epoxy composite

专利摘要:
EPOXY COMPOSITE The invention relates to a process for manufacturing an epoxy composite. In the process, an epoxy prepolymer, curing agent and particulate filler are combined to form a curable mixture. The mixture is then stirred under an airless atmosphere to make it substantially homogeneous, and pressure is applied to the mixture to reduce or eliminate gas pockets in the mixture and is maintained until the curable mixture is cured to form the epoxy composite.
公开号:BR112012033203B1
申请号:R112012033203-1
申请日:2011-06-23
公开日:2020-10-27
发明作者:Philip Michael Durbin；Ronald Charles Allum
申请人:Acheron Product Pty Ltd.；
IPC主号:

专利说明:

TECHNICAL FIELD
This invention relates to a process for the manufacture of an epoxy composite. BACKGROUND OF THE INVENTION
The inventor demanded a syntactic foam of exceptionally high and uniform resistance for flotation and as a structural element for a deep water application. Several commercial foams were tested and none were able to meet an adequate FofS (safety factor). It is considered that the failure of these materials is due in part to the non-uniformity of the materials, resulting in variable strength characteristics in different parts of the material. Commercial foams tend to fail on one side first and / or develop large cracks. Since particularly a large piece of foam was required to provide buoyancy and structural integrity for the application, the inventor considered the low FofS and the non-uniform strength of commercial foams as the main drawback.
Epoxy composites can be produced by combining an epoxy prepolymer, curing agent and filler and allowing the resulting mixture to be cured. The load can fulfill one or more of a number of purposes including stiffness, increase strength, increase crush resistance and reduce density in the cured composite. If a low load level is used, the property improvement may be less than necessary. Also, the uncured mixture can have a relatively low viscosity. This can allow partial separation of the filler (due to the different densities of the filler and the epoxy prepolymer) resulting in a cured composite with non-homogeneous ones.
These problems can be solved by increasing the charge level in the mixture. However, this results in new problems. Increasing the charge level results in an increase in the viscosity of the uncured mixture. The agitation of this mixture to obtain a homogeneous product can result in the inclusion of large amounts of air, which can generate spaces in the cured composite. These spaces can adversely affect the physical properties (strength, etc.) of the cured composite. The application of a vacuum during mixing can partially solve this problem, however, the high viscosity of an uncured composite with a high load load can make the total removal of air bubbles difficult.
Therefore, there is a need for a process to manufacture epoxy composites that reduces or eliminates spaces while allowing relatively high load loading. OBJECTIVE OF THE INVENTION
An object of the present invention is to substantially overcome or at least mitigate one or more of the above disadvantages. An additional objective is to at least partially satisfy the above need. SUMMARY OF THE INVENTION
In a first aspect of the invention, there is provided a process for making an epoxy composite which comprises combining an epoxy prepolymer, a curing agent and a particulate filler to form a curable mixture, stirring the mixture to make it substantially homogeneous and apply pressure to the mixture to reduce or eliminate gas pockets in the mixture. In the present context, the term "reduce" refers to a reduction in size (for example, volume) of gas pockets. The pressure must be maintained until the curable mixture is cured to form the epoxy composite. The stirring step, and optionally also combining, can be carried out under an airless atmosphere.
The following options can be used in conjunction with the first aspect, either individually or in any suitable combination.
The pressure applied to the mixture can be at least about 7000kPa, or it can be about 7000 to about 15000kPa. This can alternatively be about 2000 to about 7000kPa. Lower pressures can be used to manufacture composites for use at lower pressures than those made using higher pressures. Pressure can be applied isostatically. This can be applied hydrostatically. The prepolymer and curing agent can be such that the working time of the curable mixture at 20 ° C is at least about 1 hour, or at least about 6 hours, or at least about 1 day. These can be such that the curable mixture does not cure at about 20 ° C, or such that it does not cure at about 20 ° C for at least about 1 day or at least about 1 week.
The combination can be carried out by, or preceded by cooling one or more of the components of the curable mixture. This can comprise, for example, cooling the prepolymer and then adding the curing agent and particulate filler. Cooling can take place at a temperature of about 0 to about 10 ° C, for example, about 3 ° C.
The airless atmosphere under which stirring, and optionally also the combination, is carried out can be one that has a solubility in the curable mixture that is greater than the solubility of air in the curable mixture at the same temperature. The airless atmosphere can comprise at least about 50% argon on a molar basis. This can be solder gas. This can comprise about 93% argon and about 5% carbon dioxide. This can comprise about 2% oxygen. This can comprise about 93% argon and about 7% carbon dioxide.
The step of applying pressure can be carried out so that the mixture is not exposed to air. This can be done under the airless atmosphere, as described above. This can be done surrounded by a protective layer or barrier material that inhibits or prevents access of air and / or the airless atmosphere to the mixture. This can be applied isostatically by a surrounding fluid (liquid or gas), and the protective layer or barrier material can inhibit or prevent access of the surrounding fluid to the mixture.
The particulate charge may have a lower density, or actual density, than the prepolymer. This may have a lower density, or actual density, than the curable mixture. This can have an actual density less than about 0.5g / cc. The particulate charge can be, or can comprise, hollow microspheres. Hollow microspheres can be hollow glass microspheres (glass microbubbles). The hollow microspheres can be such that (for example, they can have a wall thickness such that) no more than 10% of the microspheres break during the step of applying pressure to the mixture. The particulate charge may in some cases comprise more than one degree of hollow microspheres. A grade can be a high strength grade. Another degree can be a low density degree.
The combining step may comprise combining the epoxy prepolymer, the curing agent, the particulate filler and a second filler to form the curable mixture. The second filler may comprise about 0.1 to about 1% by weight or by volume of the curable mixture.
The process may comprise heating the curable mixture to initiate or accelerating curing to form the epoxy composite. This step can be useful in cases where the curable mixture has a working time of more than about 6 hours at about 20 ° C. If a heating step is used to initiate or accelerate curing, heating can take place at a temperature below 90 ° C, or at a temperature between about 40 and about 90 ° C. This can be done at a temperature where the working time is less than about 1 hour. Heating (if used) can start at a time (referred to here as a delay time) after the start of applying pressure to the mixture. The delay time can be at least about 1 hour. If a heating step is used to initiate or accelerate curing, the epoxy composite can be cooled before the pressure is released. In this context, the term "heating to" a particular temperature refers to placing the mixture in an environment at the particular temperature and does not necessarily refer to the actual temperature reached by the curable mixture in that environment. The actual temperature, at least in parts of the mixture, may exceed the particular temperature due to the curing exotherm.
The process can be used to manufacture an epoxy composite according to the second aspect (below).
In one embodiment, a process is provided for making an epoxy composite comprising: • combining an epoxy prepolymer, a curing agent and a particulate filler composed of glass microspheres to form a curable mixture, said pre- polymer and curing agent are such that the curable mixture has a working time of more than about 6 hours at about 20 ° C, • stir the mixture under an atmosphere comprising sufficient argon and carbon dioxide to make the mixture substantially homogeneous, • apply an isostatic pressure of about 7000 to about 15000k Pa to the mixture to reduce or eliminate pockets of gas in the mixture, • heat the mixture under pressure to a maximum temperature of 90 C, the said temperature being enough to cause the mixture to be cured; • allow the mixture to cure under high pressure to form the epoxy composite, • allow the epoxy composite to cool to about room temperature, and • return the epoxy composite to about atmospheric pressure.
In another embodiment, a process is provided to manufacture an epoxy composite comprising: »combining an epoxy prepolymer, a curing agent, a particulate filler composed of glass microspheres and a fibrous filler to form a curable mixture, said prepolymer and curing agent being such that the curable mixture has a working time of more than about 6 hours at about 20 ° C, • stirring the mixture under an atmosphere comprising argon and carbon dioxide sufficiently to make the mixture substantially homogeneous, • wrap the mixture in a flexible barrier material; • apply an isostatic pressure of about 7000 to about 15000kPa to the mixture to reduce or eliminate gas pockets in the mixture, • heat the mixture under pressure to a maximum temperature of 90 ° C, the said temperature being sufficient to make with the mixture to be cured, • allow the mixture to be cured under high pressure to form the epoxy composite, • allow the epoxy composite to cool to about 60 ° C, • return the epoxy composite to about atmospheric pressure ; and • allow the epoxy composite to cool to room temperature under atmospheric pressure for at least more than 1 day.
In a second aspect of the invention, an epoxy composite is provided which comprises a particulate load and has a final stress under compression greater than or equal to 100 MPa. The composite can have a density less than about 0.7 g / cc.
The following options can be used in conjunction with the second aspect, either individually or in any suitable combination.
The epoxy composite can be made by the process of the first option.
The epoxy composite can be a syntactic foam.
The epoxy composite may have a compressive modulus so that the compression strain under 110 MPa is less than or equal to about 0.9%. This can exhibit a linear distortion less than or equal to about 0.9% under hydrostatic crushing pressure of 110 MPa.
This may have a low water absorption. This may have an equilibrium water absorption of less than about 0.5% w / w, or less than about 0.1% w / w.
The density of the particulate charge can be less than about 0.5 g / cc. The particulate charge can be, or can comprise, hollow microspheres. The hollow microspheres can be hollow glass microspheres. The particulate charge can be present in the composite at about 60% or more by volume.
The epoxy composite can additionally comprise a second filler. The second charge can be a fibrous charge. The second filler may comprise aramid fibers and / or type E glass fibers. The fibers may be about 0.2 to about 2mm of average length. The second filler can be present in the composite at about 0.1 to about 1% w / w. The epoxy composite may in some cases comprise one or more additional fillers.
The epoxy composite of the second aspect can be made by the process of the first aspect.
In one embodiment, an epoxy composite is provided that comprises a particulate load composed of hollow glass microspheres, and said composite: • has a final stress under compression greater than or equal to 110 MPa, • exhibits less linear distortion or equal to about 0.9% under 110 MPa hydrostatic compression pressure: and • has a density less than about 0.7 g / cc.
In a third aspect of the invention, the use of an epoxy composite according to the second aspect, or produced by the process of the first aspect, is provided as a structural component under compression.
The following options can be used in conjunction with the third aspect, either individually or in any combination.
Use can be made on a device for use under water. In this context, use "in" a device denotes use as part of the device, either within the device or on the surface of the device or both. The device may be suitable for use at a depth of at least about 10km under the water's surface. The use can be made at a depth of at least about 10km under the surface of the water. The device may be a manned submersible vehicle. This can be an unmanned submersible vehicle. The epoxy composite can form at least part of an external surface of said device. This can be a structural part or load bearing of the external surface of said device. This can act as a flotation element for the device. This can be a flotation element and a structural part or load bearing on the outer surface or portion of the device. The use can comprise any one or more of the following steps: • Form or cut or rub the epoxy composite in a suitable format, for example, bricks, tiles or slabs; • Arrange the composite (for example, in the form of bricks, tiles or slabs) to form a shape (for example, an iron beam) suitable for use as a structural part of a submersible vehicle or other device or a part thereof; • Fill in the gaps between the parts (for example, bricks, tiles or slabs) of the composite with a filling material capable of withstanding the conditions of use of the vehicle or other device. BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a flowchart showing a process for manufacturing a cured composite according to the present invention; Figure 2 shows electron micrographs of a) broken section and b) polished section of a cured composite filled with glass microspheres and prepared in accordance with the present invention; Figure 3 shows a temperature profile representative of the process of the invention; Figure 4 shows properties of various epoxy resins that have been hardened and cured under compression: a) compressive stress / strain curves; b) compressive module; c) Poisson's ratio; Figure 5 is a graph showing the density (g / cc) vs hydrostatic crush pressure HCP (MPa) for various commercial glass microspheres; Figure 6 shows data from a series of composites filled in accordance with the present invention; Figure 7 shows a pressure-strain curve of a syntactic foam composite under hydrostatic pressure; Figure 8 shows the compressive properties of the composite used in Figure 7: a) compressive stress / strain curves; b) compressive module; c) Poisson's ratio; Figure 9 shows a fragment of the actual composite sample used in Figure 8 after compression failure; Figure 10 shows the flexural test results of a composite according to the invention; Figure 11 shows a photograph of a fracture surface of a sample of cured composite after a bending test; and Figure 12 is a drawing of a flexion tester that shows the location of strain gauges in the sample. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following terms are used in this specification:
Epoxy: an oxirane ring or a species containing oxirane groups, or cured material derived from that species.
Prepolymer: an oligomeric or polymeric species capable of being cross-linked to form a cured resin. The degree of polymerization will generally be greater than about 3. A prepolymer is generally a liquid, which can be highly viscous or can be relatively non-viscous. Viscosities ranging from about 100 to about 1000000cP are common. Prepolymers can be referred to as resins.
Curing agent: a species capable of reacting with an epoxy prepolymer to react with epoxy groups in an epoxy prepolymer to crosslink the prepolymer to form a cured epoxy resin. The curing agent may comprise thiol and / or amine groups and may comprise a catalyst for the crosslinking reaction. Curing agents can be referred to as hardeners.
Composite: a cross-linked polymer that has particles of a charge distributed through the polymer. The cross-links can be physical, chemical and / or physical-chemical. In the present invention, the charge is a particulate charge, optionally supplemented by a second charge.
Working time: the time after mixing a curable mixture (prepolymer and curing agent) in which the mixture remains flowable.
Charge: a solid additive incorporated in a polymer (in this case, an epoxy) to modify its properties. This specification describes a particulate charge and a second charge. These terms are used simply to distinguish between different charges. It will be understood that the second charge can be particulate in nature, although, if present, different from the particulate charge.
Airless atmosphere: an atmosphere that varies from the air. The particular airless atmosphere generally used in the present invention may have a solubility in the curable mixture that is greater than the solubility of air in the curable mixture at the same temperature. The airless atmospheres used in the present invention can comprise, for example, at least about 50% argon on a molar base. A particular example is the solder gas. An atmosphere without suitable air can comprise, for example, about 93% argon and about 5% carbon dioxide. This can comprise about 2% oxygen. This can comprise about 93% argon and about 7% carbon dioxide.
Isostatic pressure: pressure applied to a body equally from all sides.
When making an epoxy composite according to the invention, an epoxy prepolymer, a curing agent and a particulate filler are combined to form a curable mixture. Commonly, though not necessarily, epoxy prepolymers and commercial curing agents are used. The appropriate reasons for these two will then be provided by the supplier. The ratio is generally within about 10% of a stoichiometric ratio (ie, the ratio where the molar ratio of epoxy groups and groups such as amines that can react with the epoxy groups). Thus, the molar ratio of prepolymer to curing agent (on a functional group basis) can be about 0.9 to about 1.1, or about 0.9 to 1.1 to 1.1 or 0.95 to 1.05, for example, about 0.9, 0.95, 1, 1.05 or 1.1. The actual weight (or volume) ratio will depend on the density of functional groups in the prepolymer and curing agent. Generally, the weight or volume ratio is about 10: 1 to about 1:10 on a weight or volume basis, or about 5: 1 to 1: 5, 2: 1 to 1: 2, 3: 2 to 2: 3, 5: 1 to 1: 1.5: 1 to 3: 1,2: 1 to 1: 1, 3: 2 to 1: 1, 1: 1 to 1: 5, 1: 1 to 1 : 2, 1: 1 to 2: 3, 1: 1 to 1:10 or 10: 1 to 1: 1 for example, about 10: 1, 9: 1, 8: 1, 7: 1, 6: 1 , 5: 1, 4: 1, 3: 1, 2: 1, 3: 2, 1: 1, 2: 3, 1: 2, 1: 3, 1: 4, 1: 5, 1: 6, 1 : 7, 1: 8, 1: 9 or 1:10. The amount of particulate filler can be sufficient to obtain a volume ratio in the curable mixture of about 60 to about 70%, or about 60 to 65, 65 to 70, 63 to 68 or 66 to 67%, for example, about 60, 61, 62, 63, 64, 65, 66, 67, 68, 69 or 70%, although in some cases this may be greater or less than that, for example, about 20, 30, 40, 50, 75 or 80%. In the case where the particulate charge comprises hollow microspheres, the amount of particulate charge can be selected so that the compaction densities are not high enough to result in a high proportion of hollow microspheres that are compressed by physical contact when the isostatic pressure is applied. There must be sufficient epoxy (ie, a sufficiently low amount of particulate charge) for the isostatic pressure to be applied to each hollow microsphere and little or no direct contact between the microspheres. These mixtures are generally sufficiently viscous to avoid component migration / separation. The amount of particulate charge can be sufficient to provide a curable mixture that does not substantially separate at rest. This may be sufficient to provide a curable mixture that has a sufficient strength limit so that it does not separate substantially at rest. This may be sufficient to provide a curable mixture with a non-zero strength limit. This can have an elastic limit of at least about 100 Pa, or at least about 200, 300, 400, 500, 600, 700, 800, 900 or 1000 Pa, or a resistance limit of about 100 to about 2000Pa, or about 100 to 1500, 100 to 1000, 100 to 500, 100 to 200, 200 to 2000, 500 to 2000, 1000 to 2000, 200 to 500, 200 to 300, 300 to 500 or 500 to 1000Pa, for example, about 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900 or 2000Pa. In some cases, a lower elastic limit may be acceptable, for example, at least about 10, 20, 30, 40, 50, 60, 70, 80 or 90 Pa, or about 10 to about 100, 10 to 50 , 50 to 100, 10 to 30 or 30 to 50Pa, for example, about 10, 20, 30, 40, 50, 60, 70, 80 or 90 Pa. The non-zero strength limit, or high viscosity, or nature The almost solid content of the curable mixture serves to ensure that the particles of the particulate filler do not separate before the mixture is cured. This in turn helps to ensure that the cured composite is homogeneous in composition, and consequently homogeneous in physical properties. In particular, since the presence of filler particles influences the strength of the cured composite, areas of different density of filler particles may have different strength properties, resulting in a total composite with reduced strength compared to a completely homogeneous composite (such as the one described here) with the same macroscopic composition, and therefore will be avoided.
As noted above, epoxy (prepolymer and curing agent) can be a commercial product. Alternatively, it can be manufactured for a particular application. In general, this will be selected for its high strength properties. As indicated elsewhere, a primary application of the present invention is in low weight, high strength syntactic foams for use in deep water applications. Epoxy can be selected to be highly resistant to hydrolysis when cured, for example, to hydrolysis by sea water under high pressure. This can be selected to have low or minimal water absorption when cured. This can be selected to have low cured density. This can be selected so that the optimum mixing ratio of prepolymer to curing agent is convenient. This can be selected so that the viscosities of the curing agent and prepolymer are suitable to produce a mixture with the particulate filler that has appropriate rheological properties (as described above). This can be selected so that the working time of the curable mixture at 20 ° C is at least about 1 hour, or at least about 2, 3, 4, 5, 6, 9, 12, 15, 18 or 24 hours, i.e. about 1 to about 24 hours, or about 1 to 12, 1 to 6, 6 to 24, 12 to 24 or 18 to 24 hours, or 1 to 7 days. This can be selected so that the curable mixture is not cured at about 20 ° C, or so that it is not cured at about 20 ° C for at least about 1, 2, 3, 4, 5, 6 or 6 days. This can be selected so that at a suitable elevated temperature below about 90 ° C, the curable mixture is cured in less than about 5 hours, or less than about 5, 3, 2, 1 or 0.5 hours , for example, cured in about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 hours. The combination of long working time at room temperature and relatively fast curing at high temperatures allows curing control, that is, curing on demand, as the curable mixture can be manipulated, molded, etc. at room temperature without premature curing and then curing started by simply raising the temperature. Curing temperatures below about 90 ° C are convenient, as these impose less stringent requirements on the equipment used to contain and manipulate the material. In addition, hazardous levels according to AS4343 are reduced when temperatures are below 90 ° C. The curing temperature can be less than about 65 ° C. This can further reduce the associated hazards. In addition, in some cases, an epoxy mixture can be cured exothermically, resulting in an additional increase in temperature. If the initial curing temperature is too high, the exotherm can increase the internal temperature of the curing mixture to the point where damage to the cured composite occurs, for example, resulting in a reduction in strength.
The inventor found that when large amounts of the curable mixture are mixed, an exotherm can occur spontaneously, resulting in cure rates that are faster than desired. Premature curing can prevent or inhibit the elimination of spaces in the mixture (since applying pressure before curing will take an insufficient time), resulting in an imperfect product. To prevent or reduce this effect, one or more components of the curable mixture can be cooled, either before or during the combining step. Since cooling is generally easier when viscosity is lower, it is common to perform cooling before adding the particulate filler, since adding the particulate filler generally results in the formation of a paste-like mixture. Thus, the epoxy prepolymer can be cooled before adding other components. In the case where a second filler is used, it is generally used in relatively low concentrations and thus generally has little effect on viscosity. Consequently, the epoxy prepolymer can be mixed with the second filler before cooling or simultaneously with cooling. Thus, one or more components can be supplied at low temperature (ie, at the cooled temperatures described below) or can be cooled as part of the process. Cooling can be at a temperature of about 0 to about 10 ° C, or about 0 to 5, 5 to 10 or 2 to 6 ° C, for example, about 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 ° C. For large batches of epoxy composite, this may take some time, for example, overnight.
A suitable process for forming the curable mixture, therefore, is as follows: a) combining the epoxy prepolymer and, optionally, second filler (for example, fibrous); b) cooling the mixed prepolymer / second charge, for example by mixing in a cold environment at about 3 ° C overnight; c) add the curing agent and continue mixing; d) add the particulate charge, optionally in several batches, and continue mixing until homogeneous; e) loading the resulting mixture into a wrapper made of a flexible water-impermeable barrier material and loading the mixture into the wrapper in a heating bath inside a pressure vessel; f) pressurize the heating bath and wrap containing the mixture to the desired pressure and maintain the pressure for an adequate delay time to allow absorption of gases in the mixture; g) heat the heating bath to about 130 ° C for about 8 hours while maintaining the pressure to cure the mixture in a cured composite; h) turn off the heating to allow the cured composite to be cooled; and i) release the pressure. Pressure release can occur when the block temperature is 60 ° C. Pressure release can be gradual, over 2, 3, 4, 5 or more than 5 steps. Alternatively, this can be continuous, for a period of about 5 to about 60 minutes, or about 5 to 30, 5 to 15, 15 to 60, 30 to 60 or 15 to 30 minutes, for example, for about 5, 10, 15, 20, 25, 30, 40, 50 or 60 minutes. The above method may be suitable for mixtures up to about 80 kg or more.
The inventor noted that in the absence of externally applied heating, a large temperature gradient can be adjusted within the curing material. It is believed that this is due to the evolution of heat due to the curing process, which can escape the external regions of the mixture more readily than the internal regions of the mixture. This large temperature gradient can result in variable properties across the resulting cured material block, possibly resulting in the formation of cracks. The external application of heat to the curing block can serve to promote a more uniform temperature distribution within the curing block and therefore more homogeneous properties. In a typical curing profile, therefore, the addition of curing agent to the epoxy prepolymer results in a slow exotherm that proceeds as the particulate charge is added. Once this is done and the final curable mixture is loaded into the heating / pressure bath container, heating starts a faster exotherm. Heating continues before the exothermic peak of the curable mixture. Once the heating is turned off, the block is allowed to be cooled slowly. The block will generally be cooled to about 60 ° C before pressure is released, or to about 50 to about 70 ° C. At these temperatures, the variability within the block is typically less than about 20 degrees Celsius. During pressure release, the block can be removed from the pressure vessel, still typically at an elevated temperature. Final cooling at room temperature can take several days.
The resulting cured block can be trimmed to have smooth, orthogonal flat faces with the desired dimensions. Typical dimensions are about 300mm x 300mm x 1300mm. The width can be about 100 to about 500 mm, or about 100 to 300, 300 to 500 or 200 to 400 mm, for example, about 100, 150, 200, 250, 300, 350, 400, 450 or 500 mm. The height can be about 100 to about 500 mm, or about 100 to 300, 300 to 500 or 200 to 400 mm, for example, about 100, 150, 200, 250, 300, 350, 400, 450 or 500 mm. The length can be about 500 to 2000mm, or about 500 to 1500, 500 to 1000, 1000 to 2000 or 1000 to 1500mm, for example, about 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900 or 2000 mm. The block may not have any externally visible cracks. This may have no internal cracks or spaces. Typically, previous methods had difficulty in producing crack-free blocks larger than about 0.02m3. By comparison, the present method can usually produce blocks free of cracks of more than about 0.1 m3.
The curable mixture may have an accelerator or catalyst or retarder to modify the cure rate. This can be a component of the curing agent or can be added separately. Suitable accelerators / catalysts are generally composed of tri-substituted amine. The accelerators / catalysts can be, for example, substituted guanidines, piperazines, imidazoles and phenolic compounds. The accelerator / catalyst can be present in the mixture in an amount sufficient to obtain the desired curing profile as described above.
The particulate filler can be any suitable filler that provides the desired properties in the cured composite containing the filler. This can be a volume charge. This can be a reinforcement charge. This can be volume and reinforcement. This can be a load to improve the buoyancy of the cured composite. This can be a load of optimization, reinforcement and buoyancy. There can be more than one charge, each, independently, with any one or more properties of volume optimization, reinforcement and fluctuation. The charge particles can be spherical, or they can have some other shape, such as ovoid, ellipsoid, cubic, rhomboid, prismatic, parallelepiped (for example, rectangular parallelepiped), oblate-spherical, acicular, fibrous, circular, polyhedral (with between fence 6 and about 50 sides), platelet-shaped, rhomboidal or may be irregularly shaped, or may be a mixture of particles of any two or more of these shapes. The particulate load can be adequate to increase the strength (in tension, shear, flexion and / or compression), increase the hardness, increase the resilience, increase the elongation at break, increase the stiffness, increase the modulus (in tension, shear, flexion and / or compression) reduce the density of the cured composite, reduce the absorption of water, increase the viscosity of the uncured mixture or for any combination of these effects. The nature and loading of the particulate load can be selected to obtain the desired properties of the cured composite. Mixtures of particulate fillers can be used to obtain these properties.
For use in deep water applications, a desired effect is to reduce the density (i.e., increase the buoyancy), and a preferred additional effect is to increase the strength under compression (and, preferably, also under bending). For this application, hollow microspheres are particularly suitable. Microspheres can be characterized in part by their actual density. This can be considered as the mass of a liquid with a density of 1.00 g / cc displaced by a microsphere completely immersed in that liquid divided by the volume of the microsphere. It will be apparent from this definition that the actual density is not affected by spaces between the microspheres, but will be affected by the confined spaces within the microspheres. The actual density of a microsphere will depend on the material from which the walls are made, the thickness of the wall and the diameter of the microsphere. The microspheres can be polymeric (for example, styrene, optionally cross-linked with divinylbenzene, acrylic, for example, polymethylmethacrylate, etc.) or they can be ceramic or glass, that is, they can be hollow glass microspheres, or they can be hollow polymer microspheres , or they can be hollow ceramic microspheres. In some cases, mixtures of two or more of these may be used.
Glass microspheres are preferred in the present invention. The actual density of the microspheres for use in the invention can be less than about 0.85 g / cc, or less than about 0.8, 0.7, 0.6 or 0.5 g / cc. This can be about 0.1 to about 0.85 g / cc, or about 0.1 to 0.8, 0.1 to 0.5, 0.1 to 0.3, 0.3 to 0 , 8, 0.5 to 0.8, 0.33 to 0.43 or 0.3 to 0.7, for example, about 0.1, 0.15, 0.2, 0.25.0, 3,0,31,0,32,0,33,0,34,0,35,0,36,0,37,0,38,0,39,0,4,0,41,0,42, 0.43.0.44, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0.8 g / cc. These may be substantially monodispersed, or may be polydispersed, or may have a polymodal (e.g., bimodal, trimodal, etc.) distribution of particle sizes. Monodispersed microspheres may have more uniform crushing resistance, while polydispersed microspheres may have improved compaction capabilities, allowing for higher particle load loads in the curable mixture. In this context, the term "substantially monodispersed" can refer to a dispersion in which less than about 10% of the microparticles (by number of particles) are more than about 10% different in diameter from the average particle diameter. . Mixtures of different grades (eg, particle sizes, different densities, etc.) of microspheres can also be used. This can be useful to improve the compaction density, allowing the use of a higher proportion of microspheres in a curable mixture. This can reduce the density of the resulting cured composite. Microspheres can have a crush strength of about 35 to about 200 Mpa (about 5000 to about 30,000 psi) or about 35 to 150, 35 to 100, 100 to 200, 100 to 150, 150 to 200, 50 to 150, 55 to 110, 35 to 70, 35 to 50, 50 to 100, 75 to 100 or 50 to 75MPa, for example, about 35, 40, 45, 50, 55, 60, 65, 70, 75 , 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200 MPa. In some cases, crush strengths less than these values may be used, for example, about 5 to about 35 MPa, or about 5 to 20, 5 to 10, 10 to 35, 20 to 35, 10 to 25 or 15 to 25 MPa (for example, about 5, 10, 15, 20, 25 or 30 MPa). These microspheres could not allow such a high curing pressure (since at higher pressures a larger proportion could cause crushing during curing), and could only be suitable for making foams for use at lower compression pressures. In this context, crush resistance is the pressure required to crush about 10% of the microspheres. This can be a hydrostatic crush pressure (HCP). Microspheres can have an average diameter of about 10 to about 200 microns, or about 10 to 100, 10 to 50, 10 to 20, 20 to 200, 50 to 200, 100 to 200, 20 to 100, 20 to 50, 50 to 100 or 15 to 30 microns, for example, about 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200 microns. These can have an average wall thickness of about 0.1 to about 5 microns, or about 0.1 to 2, 0.1 to 1.0.1 to 0.5, 0.5 to 5, 1 to 5, 2 to 5, 0.5 to 2, 1 to 2 or 0.5 to 1 micron, for example, about 0.1, 0.2, 0.3, 0.4, 0.5, 0 , 6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 microns. Preferred microspheres can have a crush strength of about 55 to 110 MPa and an actual density of about 0.3 to about 0.45 g / cc. These can have a wall thickness to diameter ratio of about 0.5 to about 10%, or about 0.5 to 5, 0.5 to 2, 0.5 to 1, 1 to 10, 2 to 10, 5 to 10.1 to 5, 1 to 2 or 2 to 5, for example, about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 , 5, 6, 7, 8, 9 or 10%. Suitable microbubbles include, for example, 3M ™ S42XHS glass bubbles, which have an actual density of about 0.42 g / cc and an isostatic crush resistance of about 8000 psi (about 55MPa). It is believed that the weaker hollow microspheres (i.e., those that could fail when HCP is determined) can weaken the cured epoxy composite if they resist the process of making the mixture. Therefore, it is considered preferable that these microspheres are crushed so as to become a solid (not hollow) charge in the curable mixture. It should be noted that the wall thickness / diameter ratio is likely to determine the HCP of a microsphere. The weak microspheres can have any size and can be those that have less sphericity or thinner walls. Higher density microspheres may simply have thick walls.
Microspheres can be classified. Thus, the classification can remove the microspheres above a selected size or it can remove the microspheres below a selected size. Smaller microspheres may have a reduced void ratio, thus impairing density-reducing properties, while larger microspheres may have less crushing resistance. These can be crushed during production, thereby impairing the density reducing properties.
In some cases, microspheres can be surface treated or surface coated. This can improve the interaction between the epoxy matrix and the microspheres. This can improve the adhesion between the epoxy matrix and the microspheres. This can increase the strength and / or resilience and / or hardness of the composite. Suitable surface treatments include epoxy silane treatments (for example, glycidoxypropyltrimethoxysilane CH2 (O) CHCH2OC3H6-Si (OCH3) 3) to bind the epoxy groups to the surface of the microspheres or treatments with aminosilane (for example, with NH2C3H6-6 aminopropyltrietoxysilane Si (OC2H5) 3) to connect the groups to the surface of the microspheres). In other cases, the microspheres are not surface treated or surface coated.
There may be more than one type of microspheres used in the invention. For example, higher density microspheres can be used for improved strength in combination with lower density microspheres for reduced density of the epoxy composite.
It may be useful to use a second charge, and optionally additional charges. Each of these, independently, may be fibrous or may be non-fibrous. Non-fibrous fillers include polyolefin microspheres (for example, polypropylene) or macrospheres (hollow or solid). These can have a diameter of about 1 to about 20 mm, or about 1 to 10, 1 to 5, 1 to 2, 2 to 20, 5 to 20, 10 to 20, 15 to 20, 5 to 15, 2 to 5, 5 to 10 or 10 to 15 mm, for example, about 1,2, 3, 4, 5, 6, 7, 8, 9. 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 mm. The macrospheres can be made of epoxy resin reinforced with carbon fiber or glass on polystyrene spheres that are manufactured using rotational casting. Suitable macrospheres are available from Cumming Corporation or Matrix Composites and Engineering Ltd. These have the typical properties set out below: density less than 0.4g / cc, compressive strength greater than 17 MPa, compressive modulus above 08Gpa. Tests of HCP (hydrostatic crush pressure) on the foam of the present invention indicate that it is capable of supporting a hole 16mm in diameter, 12mm below the surface without implosion. That being the case, it is clear that the macrospheres can safely be added to the curable material as long as they have the appropriate curable material around them (that is, there is sufficient distance between the macrospheres), and still produce a cured product that can withstand the isostatic pressure so that it is designed and / or is strong enough to maintain the required hydrostatic crush resistance of the syntactic foam while making it less dense. Suitable fibrous fillers can be aramid fibers (for example, Kevlar® fibers) or type e glass fibers. Type E glass is aluminum borosilicate glass with less than about 1% 5 by weight of alkali oxides, commonly used for fiber reinforcement. Second and optionally additional charges can be individually or in combination present in about 0.1 to about 1% by weight of the curable mixture, or about 0.1 to 0.5, 0.1 to 0.2, 0.2 to 1.0.5 to 1 or 0.2 to 0.5%, for example, about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1% w / w. The 10 fibers (if the second filler is fibrous) can have an average fiber length of about 0.2 to about 2 mm, or about 0.2 to 1.0.2 to 0.5, 0.5 to 2, 1 to 2 or 0.5 to 1.5mm, for example, about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0, 9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2 mm, or may in some cases be larger than 2 mm. The second load can improve the tensile strength of the cured epoxy composite. This can improve your stiffness. This can improve your crush resistance. This can enhance any or more, optionally all, properties by at least about 5%, or at least about 10%, for example, by about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15%, with respect to the same material devoid of the second charge. A benefit of using aramide or other organic fibers (for example, polymeric, aramid etc.) as the second filler is, the improvement in properties with relatively less impact, or in some cases no impact on the density of the final composite.
Once the components of the curable mixture have been combined, the resulting mixture is stirred, for example, mixed sufficiently (i.e., for a sufficient time and at a sufficient rate) to make it substantially homogeneous. This can be done, for example, using a mixer or agitator. The combination (described above) and optionally also stirring can be conducted under an airless atmosphere. The inventor has discovered that a small amount of carbon dioxide in the airless atmosphere can have a beneficial effect on the strength of the resulting cured composite. The concentration of carbon dioxide can be about 1 to about 10%, or about 1 to 5, 1 to 2, 2 to 10, 5 to 10 or 3 to 8% on a volume basis, or about 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10% by volume. In some cases, higher concentrations, for example, about 10 to about 50% (or about 10 to 40, 10 to 30, 20 to 50, 30 to 50 or 20 to 40%) can be used, for example, about 10, 15, 20, 25, 30, 35, 40, 45 or 50% by volume. The presence of carbon dioxide is believed to affect the gas / mixture interface to reduce the size of included gas pockets. It is also believed that carbon dioxide can inhibit or delay the curing of the epoxy resin, thus allowing more time for the elimination or reduction of spaces (gas pockets) in the mixture before curing (see below). This may be the result of an effect of carbon dioxide on the curing agent. However, the inventor found that if the concentration of carbon dioxide in the airless atmosphere is too high (for example, 100%), the density of the cured composite is greater than it could be. This is a disadvantage for deepwater applications or other applications that benefit from the low density of the composite, although the use of 100% carbon dioxide may be appropriate in cases where the low density of the composite is not critical. It may be possible to replace at least a portion of the carbon dioxide with other gases that perform a similar function, for example, sulfur dioxide, nitrogen oxides or mixtures of these gases. The remainder of the airless atmosphere, or most of the remainder, may be a gas that has greater solubility in the curable mixture than air. A suitable gas is argon. Krypton, xenon or other chemically inert gases can also be used. The preferred gas can be heavier than atmospheric gas. In some cases, lighter gases than atmospheric gases may be used instead of argon, for example, helium. Mixtures of gases (eg helium / argon / carbon dioxide, neon / argon / carbon dioxide etc.) can also be used. In some cases, mixtures with nitrogen may be used. Nitrogen can be in a lower proportion than in air, for example, less than about 70, 60, 50, 40, 30 or 20% by volume, or it can represent about 10, 20, 30, 40, 50, 60 or 70% of the atmosphere without air by volume. A preferred gas is one that has relatively high solubility in the curable mixture (for example, greater solubility than air) and relatively low solubility in the cured composite (to allow it to cure the composite and then reduce the density of the composite). This can be beneficial in stimulating the gas solution in the mixture before curing, so that any spaces that are present in the mixture are capable of being reduced or eliminated. It is believed that the reduction and / or elimination of gas pockets may be due in part to a simple reduction in the size of the gas in the bag due to the increased pressure (according to Boyle's law) and partially due to the absorption of gas in the bag within the surrounding matrix due to the increased solubility of the gas in the matrix at high pressure. After curing, it is believed that at least some dissolved gas will spread out of the composite. This can serve to reduce the density of the composite without introducing spaces. The airless atmosphere can be heavier than air, although if appropriate, detention equipment is used, gases lighter than air can be used. The gas can have a density relative to air at the same pressure of at least about 1.05, or at least about 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45 or 1.5, or about 1.05 to 2, 1.05 to 1.8, 1.05 to 1.5, 1.05 to 1.3, 1.1 to 2 , 1.2 to 2, 1.5 to 2 or 1.1 to 1.5, for example, about 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2. The airless atmosphere can comprise, for example, 90 to 95% argon (or another suitable gas as described above), or 90 to 93 or 92 to 95% argon or other suitable gas, for example, about 90, 91, 92, 93, 94 or 95% argon or other suitable gas, by volume. This can comprise argon and carbon dioxide. This can comprise carbon dioxide as a secondary component (for example, about 1 to 10%) and argon as a main component (for example, about 90 to 95%). This can be, for example, a welding gas. For mixing under an airless atmosphere heavier than air, it may be sufficient to have a flow of gas flowing over the mixture as it is mixed, however, the gas can be alternatively or additionally bubbled / spread over the mixture. The appropriate gas flow rate will depend on the size of the mixture, however, representative flow rates are between about 1 and about 1 minute, or about 1 to 5, 1 to 2, 2 to 10, 5 to 10, 2 at 5 or 2 to 3LJmin, for example, about 1.2, 3, 4, 5, 6, 7, 8, 9 or lOLVmin for about 2 to 3kg of curable mixture. For larger amounts of curable mixture, the flow rate can be proportionally higher. The mixing is usually carried out at or below room temperature to prevent premature curing of the mixture. This can be conducted, for example, at about 15 to about 30 ° C, or about 15 to 25, 15 to 20, 20 to 30, 25 to 30 or 20 to 25 ° C, for example, about 15, 20, 25 or 30 ° C. As discussed, it can be below these temperatures, for example, as low as about 0 ° C. It may be necessary to mix for at least about 30 minutes, or at least about 1,2, 3, 4, 5 or 6 hours to achieve an acceptable degree of homogeneity in the curable mixture, however, this will depend to some extent on viscosity of the mixture. In some cases, shorter mixing times can be effectively used, for example, about 1 to about 30 minutes, or about 1 to 15, 1 to 10, 1 to 5, 1 to 2, 2 to 30, 5 at 30, 10 to 30, 20 to 30, 2 to 15, 2 to 10, 2 to 5, 5 to 10 or 10 to 20 minutes, for example, about 1,2, 3, 4, 5, 6, 7 , 8, 9,10,15, 20, 25 or 30 minutes.
Once the mixture has reached an acceptable degree of homogeneity, it is pressurized to reduce or eliminate pockets of gas in the mixture. In this context, "reduce" refers to a reduction in the size or volume of gas bags (spaces). "Eliminate" refers to the disappearance of gas pockets (spaces). It is believed that this is at least partially due to the gas in the gas pockets (spaces) being absorbed / dissolved in the curable mixture. This step is preferably carried out in such a way that the mixture is not exposed to the gas (instead trapped or dissolved in the mixture). This avoids adding additional gas to the mixture which could reduce the ability of the mixture to absorb the gas present in the existing spaces. The pressure can be applied substantially in an isostatic manner. A convenient way to apply pressure to the gas is to wrap it in a barrier material, immerse the mixture involved in a liquid and apply the desired pressure to the liquid. A simple method for wrapping the mixture is to place it on / over a film of the barrier material, fold the barrier material around the mixture to completely surround it and secure the ends of the barrier material, for example, by twisting and / or mooring (for example, with a loop, string or some other suitable method). In this method, the barrier material can be wrapped around the curable mixture in a cylindrical manner. The ends can then be twisted (like a sausage) and then clamps or other suitable fastening devices are used to secure the ends. Alternatively, the wrapping can be done in a cylindrical manner and the alternating end attached to the end wraps in at least two directions as well as additional cylindrical wraps. The barrier material can be a single layer 10 barrier material or can have multiple layers (e.g. 2, 3, 4 or 5 layers) to enhance the barrier properties. The barrier material can be folded around the curable material to form an approximately rectangular parallelepiped shape. In some cases, a sealing material can be used to seal the barrier material. This can be a pressure-resistant adhesive, for example, a butyl mastic tape. In other cases, the barrier material can be thermally sealed. The barrier material may be in the form of a six-sided screw box sealed at 4 edges by a sealant and having an upper and lower diaphragm. The diaphragm allows the applied pressure to compress the mixture inward. 20 An additional option is to use a folded polypropylene box sealed with a sealing material, for example, double-sided black butyl mastic tape, as one or more outer layers (eg 1, 2, 3, 4 or 5) of film PVC welded as a tank liner and resealed with double-sided black butyl mastic tape. The PVC liners and the polypropylene box can then be placed in the six-sided screw box which is no longer sealed. In an additional option, the curable mixture can be placed on an open tray and sealed with a flexible membrane, which can be attached to the upper edges of the tray. In this option, a release agent can optionally be used on the bottom and / or sides 30 of the tray. Suitable release agents include, for example, silicone release agents. Alternatively, the tray may have a non-adhesive surface, for example, a polymeric J fluorocarbon surface. The wrap can be a single layer wrap. This can have multiple layers (for example, 2, 3, 4, 5, 6, 7, 8, 9 or 10 layers wrap). Suitably, the curable mixture can be inserted into a pouch made of the barrier material. This can then be sealed, for example, thermally sealed to prevent the ingress of the liquid where it is compressed. Sealing can be performed to include as little gas as possible inside the barrier material (ie, inside the bag). In some cases, the mixture can be first wrapped and then sealed in a bag. The pressure in the liquid will then be transferred substantially isostatically to the mixture. A suitable barrier material must be flexible to absorb changes in the dimensions of the mixture under pressure and transfer the pressure from the surrounding fluid to the mixture. This must be substantially impermeable to the liquid. This can be strong enough to withstand the forces to which it is subjected in use. It must also be able (that is, to have an appropriate softening and / or melting temperature) to withstand the temperature during curing of the curable mixture. Suitable barrier materials include polymeric films, for example, polyethylene film, PVC film, latex film, polyurethane film, EPDM rubber, etc. In the case of multilayer barrier materials, the different layers can be of the same material or they can be different. The wrap should be such that, under the applied pressure, none (or negligible amounts) of the liquid will penetrate the mixture, at least until the curable mixture is cured to form the cured composite. In some cases, examples of barrier materials may fail below about 90 ° C (for example, they may shrink, become brittle and / or deteriorate). However, when the mixture (and barrier materials) reaches that temperature, the mixture will be cured to a substantial degree (and will simply go through a final transition phase, effectively after curing, to further increase the strength) and therefore it will be impermeable to the liquid, so any penetration of the liquid will not cause problems. The liquid can be aqueous (for example, water) or it can be non-aqueous (for example, silicone fluid, mineral oil, etc.) or it can be some other type of liquid. The liquid can have a viscosity of about 0.5 to 200cS, or about 1 to 200, 10 to 200, 50 to 200, 0.5 to 100, 0.5 to 50, 0.5 to 10, 0, 5 to 2, 1 to 100, 1 to 50, 50 to 100, 1 to 20 or 20 to 50cS, for example, about 0.5, 1, 1.5, 2, 2.5, 3, 3.5 , 4, 4,5, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 140, 160 , 180 or 200cS. In some embodiments, the curable mixture involved can be compressed by means of a gas instead of a liquid. In that case, the barrier material must be substantially gas-impermeable. It should be noted that in some cases the barrier material is not completely impermeable to the surrounding liquid and some liquid may leak into the mixture located there.
The pressure applied to the curable mixture can be approximately equal, or less, to that which was designed to withstand in use. This can be about 5% to about 100% of the projected usage pressure, or about 5 to 50, 5 to 20, 5 to 10, 10 to 100, 20 to 100, 50 to 100, 10 to 50, 10 to 20 or 5 to 20%, for example, about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90 or 100% of the projected pressure of use. In particular modalities, this will be about 10% of the projected usage pressure. This can be enough pressure to rupture about 5 to about 15% of microsphere charge particles, or about 5 to 10 or 10 to 15% of these, for example, about 5, 10 or 15% of these . The small proportion of broken microspheres can then act as a charge to provide resistance to the resulting cured composite. The pressure can be a pressure of at least about 7000kPa (about 10000psi), although in some cases pressures below that value can be effective, for example, pressures of about, or at least about, 3000, 3500 (about 500psi), 4000, 4500, 5000, 5500, 6000 or 6500kPa, or about 3000 to 7000, 3000 to 5000, 5000 to 7000, 4000 to 6000 or 4000 to 5000kPa. Lower pressures can be used to produce composites with a lower depth rating. These foams may have less strength and / or lower density than those cured at higher pressures. The pressure can be at least about 7500, 8000, 8500, 9000, 9500 or 10000kPa, or it can be about 7000 to about 15000kPa, or 7000 to 10000, 7000 to 8000, 8000 to 15000, 10000 to 15000, 8000 to 12000 or 8000 at 10000kPa, for example, about 7000, 7500, 8000, 8500, 9000, 9500, 10000, 11000, 12000, 13000, 14000 or 15000kPa. If the pressure is too low, the required degree of clearance elimination may not be achieved, resulting in a cured composite that has insufficient crushing (or compressive) resistance. If the pressure is too high, excessive numbers of microspheres or other particles of particulate charge may be crushed or broken, in the case where the particles of particulate charge are crushable or ruptured. This can result in the production of a cured composite that has a higher density than desired, and can cause other unwanted physical properties (although it can increase the strength of the cured composite). It is estimated that a pressure of about 7000kPa can result in a reduction in space size of at least about 70 times, and that as the gas in a space dissolves in the curable mixture, the spaces can reduce substantially more than that and can disappear completely.
In some cases, pressure may initially be applied at a temperature at which the curable mixture is not rapidly cured (for example, it is not cured within about 2 hours, or within about 3, 4, 5, 6, 7 , 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 hours). This initial compression phase can occur at approximately room temperature. This can be about 15 to about 30 ° C, or about 15 to 25, 15 to 20, 20 to 30, 25 to 30 or 20 to 25 ° C, for example, about 15, 20, 25 or 30 ° C. This allows time to reduce or eliminate gas spaces in the mixture before curing. The curable mixture can be compressed at the temperature defined above for about 1 to about 20 hours, or about 1 to 10, 1 to 5, 5 to 20, 10 to 20, 15 to 20 or 10 to 15 hours, for example , about 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 hours. This time can be referred to as a delay time. In some cases, the temperature during this phase (delay period) may be below 15 ° C, for example, about 0 to about 15 ° C, or about 0 to 10, 0 to 5, 5 to 10 or 5 to 15 ° C, for example, about 0, 5, 10 or 15 ° C. Compression at a lower temperature can be an advantage, since the curable mixture will cure more slowly at a lower temperature, allowing a longer time for spaces to be reduced or eliminated (for example, absorbed). Additionally, since the gases are generally more soluble at lower temperatures, the dissolution of gases in the compressed spaces is stimulated at lower temperatures, allowing for a greater reduction in empty volume.
After the initial low temperature compression phase, the temperature can be raised to a curing temperature to cure the curable mixture. The temperature can be increased, for example, by increasing the temperature of a liquid where the curable mixture is immersed (preferably, enclosed in a barrier material as described above). The curing temperature can be less than about 90 ° C, or less than about 80, 70 or 60 ° C. This can be above about 40 ° C, or above about 50. 60 or 70 ° C, or it can be about 40 to 90, 40 to 80, 40 to 65, 40 to 60, 50 to 90, 70 at 90 or 50 to 80 ° C, for example, about 40, 45, 50, 55, 60, 65, 70, 75, 80, 85 or 90 ° C. Curing temperatures of about 90 ° C or more can be used in some cases, for example, up to about 170 ° C, or up to about 160, 150, 140, 130, 120, 110 or 100 ° C, for example for example, about 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165 or 170 ° C. The curable mixture can be increased and maintained at the curing temperature without reducing pressure, that is, maintaining the pressure as described above. Thus, after mixing, optionally under an airless atmosphere, and subsequent wrapping in a barrier material if required, the pressure is increased to the desired pressure and maintained until the curable mixture is cured to form the cured composite. In some cases, the pressure can be additionally increased before or during the high temperature curing phase, or it can be slightly reduced, however, it must be kept within the desired range (described above). Generally, the increased pressure is kept substantially constant by curing the cured composite. The curing temperature can be maintained long enough to cure the curable mixture. This can be maintained for at least about 2 hours, or at least about 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 hours, or for about 2 to 12, 4 to 12, 6 to 12, 8 to 12, 2 to 10, 2 to 6 or 6 to 10 hours, for example, for about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 hours. The curing time will depend on the nature and reasons of the components of the curable composite (particulate filler, epoxy prepolymer and curing agent) as well as on the nature, presence or absence and quantity of other components such as an accelerator. The curing temperature can be one in which the curing time, or working time, of the curable mixture is less than about 1 hour, or less than about 2, 3, 4, 5, 6.7,8,9,10 , 11,12,13,14, 15, 16, 17, 18, 19 or 20 hours, for example, the curing temperature can be such that the working time, or curing time, is about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 hours. In some cases, a post-cure can be performed, either before or after pressure relief (ie, it returns to approximately ambient pressure). Post-curing can occur under conditions (temperature, time) as defined above for curing. This may be in the same condition as the cure or under different conditions.
As described above, heating can take place by means of a heated liquid bath. In this case, the liquid in the bath can be recirculated to the bath via a temperature controller that maintains the desired temperature. In addition to providing the heating required to increase the bath temperature to the desired curing temperature, this can also serve the purpose of removing excess heat developed as a result of an exothermic curing reaction, to prevent the curing mixture from overheating. In addition or alternatively, heating can take place using an electrical wire or some other suitable method.
If a heating step is used to start curing, the epoxy composite can be cooled before the pressure is released. Cooling can be done by removing the cured composite from a liquid in which it is immersed for heating, or it can be done by cooling the liquid in which it is immersed. The cured composite can be cooled to room temperature before the pressure is released, or it can be cooled to a temperature less than or equal to about 40, 35, 30, 25 or 20 ° C, or to a temperature of about 40, 35 , 30, 25 or 20 ° C. In some cases, it can be cooled to a temperature of 45, 50, 55, 60, 65 or 70 ° C before the pressure is released. The latter ranges are more common with larger product samples, as the time required for cooling is considerably longer for these large samples.
In summary, a suitable process for producing the epoxy composite of the invention comprises the following steps. The time suggested below is suitable for producing about 1 to 2 kg of cured epoxy composite, however it may require different times (for example, longer) for larger batches and these may require a slightly modified process. • an epoxy prepolymer and curing agent are mixed under an airless atmosphere (for example, while being spread with the airless atmosphere), usually for about 3 to 4 minutes; • hollow glass microspheres are then added to the combined prepolymer / curing agent. This may involve adding two or more different degrees of microsphere. In this case, the microspheres of greater resistance (higher) or higher real density (higher) can be added first. The resulting curable mixture is then mixed under the airless atmosphere for about 5 minutes until it is homogeneous. The total time for this and the previous mixing step, including the addition times, can be about 10 to 15 minutes. o The curable mixture is then wrapped in a polymeric film. This may involve coating a mold with the film, adding the curable mixture to the coated mold and then completing the wrap. The mixture involved can then be inserted into a pouch made of a thermally sealable plastic film which is then thermally sealed to further protect the mixture. The wrapping and sealing in the bag must be carried out with the inclusion of as little gas as possible (air atmosphere or without air) inside the wrap or sealed bag. • the mixture involved is then immersed in a liquid, for example, water or low viscosity silicone fluid, and hydrostatically compressed to the desired pressure (about 7 to about 15MPa). This pressure is maintained for about 6 to 8 hours at or below room temperature (usually about 10 to about 25 ° C). • the temperature is then raised to the desired curing temperature (usually around 50 to 90 ° C) while maintaining pressure. The time to increase the temperature can be about 4 to 6 hours. The elevated temperature and pressure are then maintained for about 6 to 8 hours to cure the mixture to form the composite. A post-curing step at about 120 ° C for about 1 to 3 hours is optional. • the cured composite is then allowed to cool to around room temperature (typically around 20 to 40 ° C) while maintaining high pressure. • once the composite temperature returns to almost room temperature, the pressure can be removed.
After the epoxy composite is made, as described above, it can be formed, for example, cut, sawn, machined, ground, scraped, crushed, etc., to a desired shape. This can be formed into blocks, bricks, slabs or another convenient format. This can be formed, for example, in a format suitable for building a structural part or component for a deep water submersible vehicle. Alternatively, the curable mixture can be shaped into a desired shape before curing, so that it is cured to form curable composite pieces in the desired shape. In use, blocks or other shapes of the composite can be adhered, for example, to build a structural beam. The adhesive can be an epoxy adhesive. This can be a high strength epoxy adhesive. This can be a filled epoxy adhesive. This can be an epoxy adhesive filled with a microsphere. The microspheres can be polymeric, glass or ceramic microspheres. If the glass microsphere filled epoxy adhesive is used, the epoxy and / or the microspheres can be as described here. The epoxy and / or the microspheres may, independently, be the same as those used in the manufacture of the composite, or they may be different. In use, the composite structural shell may have a cover or coating. This can be a plastic cover or coating. This can be a blanket or fabric covering. This can be a cover or protective coating. This may comprise, for example, a polymeric filled cover or coating (for example, filled with boron fiber, Kevlar® fiber and / or carbon fiber). This may comprise a fibrous fabric covering or covering, for example, boron fibers, Kevlar® fibers and / or carbon fibers or polyester or polypropylene cloths. The cover or coating may be in the form of a flexible film. The cover or coating can be laminated with the epoxy composite. This can be flexible enough that it is not easily delaminated in use. The cover or coating can help the composite to resist the high pressures found in use.
An epoxy composite according to the present invention may have a final stress under compression (or crush strength) greater than or equal to 100MPa (about 14500psi), or greater than or equal to about 105, 110, 110 or 120MPa, or from about 100 to about 120MPa, or about 100 to 110, 100 to 105, 105 to 120 or 105 to 110MPa, for example, about 100, 101, 102, 103, 104, 105, 106, 107, 108 , 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119 or 120MPa. The final stress described above refers to the applied stress at which the composite is found. This is usually a catastrophic failure, in which the sample breaks. The composite may have a compressive module such that, at a pressure of 110MPa (or at the limit of its crush resistance, whichever is less), it exhibits a deformation less than or equal to about 3%, or less than or equal to about 2.5, 2, 1.5, 1, 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55 or 0, 5%, This can exhibit a linear distortion less than or equal to about 1.3% under hydrostatic compression pressure of 110MPa, or less than about 1.2, 1.1, 1, 0.9, 0.8, 0.7, 0.6 or 0.5, for example, a linear distortion of about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0 , 9, 1, 1.1, 1.2, or 1.3%. By comparison, commercial syntactic foams typically exhibit compressive strain (or linear distortion) of about 1.4% or more under similar conditions. By using suitable microspheres as a particulate charge (as previously described), a density less than about 0.8 g / cc can be obtained with the strength and modulus values described above, or a density less than about 0.75 , 0.7, 0.65 or 0.6 g / cc or from about 0.5 to about 0.8 g / cc or about 0.5 to 0.7, 0.5 to 0.6, 0.6 to 0.8 or 0.6 to 0.7 g / cc, for example, about 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0, 8 g / cc. The epoxy composite may have low water absorption. This can have an equilibrium water absorption of less than about 0.5% w / w, or less than about 0.1% w / w. This can be measured approximately at atmospheric pressure or at a pressure of about 110MPa, or at a pressure of about 110MPa, or at a pressure of about 125MPa. Water absorption can be less than about 0.4, 0.3, 0.2, 0.1, 0.05, 0.02 or 0.01%, or it can be about 0.01, 0, 02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5% w / w. By comparison, the previously known syntactic foams have a water absorption of about 3% by weight at about 18000psi (about 125 MPa). Water absorption values are measured at room temperature, for example, at about 20 or 25 ° C. The cured composite may have a tensile strength greater than about 20MPa, or greater than about 25, 30, 35 or 40MPa, or about 20 to about 50MPa, or about 20 to 40, 30 to 50 or 30 to 40MPa, for example, about 20, 25, 30, 35, 40, 45 OR 50MPa.
The cured composite may have a module under compression of at least about 2GPa, or at least about, or about 2 to about 9GPa, or about 2 to 8, 2 to 6, 2 to 4, 3 to 8, 5, 5 to 8.5, 7 to 8.5, 4 to 8, 6 to 8, 4 to 6, 2 to 3, 3 to 4, 2.5 to 4 or 2.5 to 3.5 GPa. This can have a module of about 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8 or 8.5GPa. It can have such a module in a deformation of up to about 3%, or up to about 2.5, 2, 1.5, 1.0.5 or 0.1%.
An important aspect of the composite described here is the combination of high crush strength (ie, compressive strength) with low density, making it suitable for structural applications in deep water. Other properties that can be combined with this combination include high break resistance, low compressibility (ie, high compressive modulus), high stiffness and homogeneity of physical properties over a large composite block. Important aspects of the process that allow these products to be obtained include: • selection of suitable raw materials, in particular low density fillers and optionally a second filler (usually fibrous): the particular degree of raw material can be important to obtain properties acceptable; • use of adequate component ratios so that the uncured mixture has sufficient viscosity to prevent the separation of components (particularly fillers); • use of a combination of prepolymer and curing agent that allows very slow curing at room temperatures and relatively fast curing at high temperatures. In some cases, this allows healing on demand. In large blocks, the mixture can be cured without external heating due to a very slow rise in temperature that has been observed to rise by around 50 ° C. It is believed that this may be due to the insulating properties of the glass or simply to the epoxy mass. For smaller blocks, the heat loss of the mixture can overcome the exotherm, so that external heating is required to cure the mixture, providing the cure on demand; • mixing under a suitable airless atmosphere so that any entrained bubbles / gas pockets can reduce in size and / or be absorbed into the mixture under compression; • compression of the curable mixture at a temperature at which curing is very slow, and this compression lasts long enough to allow absorption of gases in the mixture before curing; • external application of heat to accelerate curing and reduce temperature gradients within the curing mixture. The external application of heat also provides a post-cure for the resin. Epoxy resin generally requires 8 h at 80 ° C to achieve its optimum HDT (thermal distortion temperature) which the inventor considers to be best conducted under high pressure. Thus, the external application of heat can activate / accelerate curing, reduce temperature gradients and provide a post-cure cycle for the curing mixture.
The cured composite of the invention, particularly when made with hollow microspheres as a particulate charge, may be suitable for use in deep water applications. This may be able to withstand the pressures that operate in the deepest part of the ocean (about 11000m). This may be able to withstand hydrolysis in seawater at the pressures that operate at that depth. This can be floating in sea water. This can be suitable for use as a fluctuation element and / or as a structural element at that depth. This can be, for example, suitable for use on the outer surface of a submersible vehicle that will be used in the deepest part of the ocean, and can additionally provide 10 buoyancy in that application. This may be suitable for use as a jacket for deep water oil pipelines. It may have thermal and / or acoustic properties suitable for deep water applications. It can have any combination of the above properties suitable for the application in which it will be used. 15 For use in aqueous environments, low water absorption can be
a benefit. The composite of the invention can have a water absorption of less than about 0.5% under conditions of use (for example up to 11000m in depth), or less than about 0.4, 0.3, 0.2 or 0 , 1% on a weight basis, or about 0.05, 0.1.05, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0 , 5%. 2 0 At a depth of about 11000m in seawater, the pressure is about 16500psi (about 114MPa). At these pressures, the water absorption of the cured composite described here may be zero or may be negligible. It is believed that the particular manufacturing process, in which the composite is cured under high pressure, combined with the high level of particulate filler (which leaves relatively small amounts of potential water-absorbing organic matrix) provide this excellent absorption property of water.
The use of microspheres, particularly glass microspheres, as a particulate filler in the cured composite can also serve to improve the thermal and / or acoustic insulation properties of the composite, which can be beneficial in certain applications.
In a particular embodiment, the epoxy composite of the present invention is manufactured using hollow glass microspheres with epoxy resin. However, unlike other syntactic materials, the present composite has resistance 'isos' or equal (iso as a prefix, from the Greek word 'isos' means equal). Equal (or uniform) properties are obtained by adopting a special manufacturing process that is different from the prior art. The following description is a guideline for a suitable process for manufacturing the epoxy composite of the invention:
A high compaction density of hollow glass microspheres for epoxy resin is selected so that the mixture becomes plastic or almost solid. The light hollow glass microspheres that could normally migrate and float to the surface in liquid form are less able to migrate quickly in a high viscosity plastic or mixture.
The mixture of hollow glass microsphere and epoxy resin is mixed and compacted in a mold under an artificial atmosphere. An atmosphere of 5% CO2 with argon is suitable since both gases are easy to obtain (separately and / or already mixed as a solder gas). Also, since both gases are heavier than air, it is easy to create an artificial atmosphere over the microsphere / resin mixture using simple equipment, for example, a flow meter and open hose. Similar results are expected with other gases and / or a mixture of other gases including gases lighter than air with a special mixture and wrap spaces to contain the artificial atmosphere (s).
The mixture involved is then sealed in an airtight and liquid package. Wrapping in multiple layers of “adhesive” type film, sealed plastic bags or special flexible mold liners has been used successfully.
The now sealed mixture is placed in a pressure vessel and pressurized with liquid. A non-hazardous thermally conductive liquid such as water is suitable, however, other liquids can also be used. The pressure is selected depending on numerous factors such as the HCP (hydrostatic crush pressure) of the hollow glass microspheres, compaction density, etc. The ideal pressure will flatten weak hollow glass microspheres that are unwanted without causing excessive compaction so that stronger hollow glass microspheres are crushed by physical contact with each other.
Delayed curing of the epoxy resin is highly preferred to allow as much of the entrained gas that is present in the mixture to be absorbed into the liquid epoxy resin (already mixed with the curing agent). The hydrostatic pressure maintained during the curing of the resin and any additional post-cure cycle, even returns to room temperature before the pressure is released.
The various characteristics of the above process, including selecting the correct compaction density, type of hollow glass microsphere, epoxy resin system, artificial atmosphere gases, applied hydrostatic pressure, curing temperature and curing cycle times are important for the process . It is a more collaborative process that produces the syntax with the best results.
The inventor believes that CO2 can change the surface tension of the epoxy resin and / or it can act as a retarder to allow the epoxy resin to remain liquid longer. Both effects could allow more gas to be absorbed into the liquid epoxy resin before it gels or hardens to a solid. Argon acts as a diluent for C02, since the inventor found that too much CO2 in the epoxy resin can have an adverse effect, and can be more absorbent in liquid epoxy resin than air.
In prior art processes, hollow glass microspheres and epoxy resin are generally mixed with an aqueous paste and then poured into molds for curing. Superior quality foams are mixed under vacuum conditions to minimize trapping of air and carefully dumped to prevent more air from entering the mixture. Captured or trapped air is not desired, as it reduces HCP (hydrostatic crushing pressure) and hardness (measured in deformation), but increases fluctuation and insulation and therefore some air / gas in the mixture has traditionally been accepted.
The hollow glass microspheres / epoxy resin system was considered potentially suitable for the application, however, the mixing of ingredients under a vacuum was considered difficult and undesirable. Other low-density and hollow fillers have been considered, but hollow glass microspheres offer the highest crushing resistance ratios for density compared to other types. Also, other bonding agents have been considered, but epoxy resin systems have a different advantage with better compressive strength to density ratios and are virtually impermeable to water ingress.
To overcome the need for vacuum mixing, the inventor developed a process that involves mixing the ingredients at much higher compaction densities and then isostatically compressing the mixture in a pressure vessel and allowing them to be cured under pressure. It was believed that it could create a foam substantially free of air (or at least a foam with reduced amounts of air) since any air spaces could be made smaller by compression (Boyle's law) and could be absorbed into the liquid epoxy resin before to harden (Henry's law). It must be recognized that "air-free" in this context refers to microspheres outside the air, provided that the process clearly does not affect the air trapped inside the microspheres. The inventor considers that any compressed / absorbed air can be decompressed outside the cured composite and causes problems. There is no direct evidence that this does, however, air is not a concern.
A large number of cured composites were prepared with different compaction densities of hollow glass microspheres in epoxy resin, following the recommended post-cure cycles and using different isostatic pressures. Higher compaction densities of the particulate load were considered to provide a more uniform foam, since, in high compaction density mixtures, hollow glass microspheres are unable to migrate if the mixture is mixed to a mass-like consistency. This is an important step in achieving a foam of uniform density and strength.
Initially, the foams produced (mixing in air) seemed to be free of spaces, however, it was evident that large air pockets were not absorbed in the epoxy resin and were trapped in the foam. Bending tests revealed that the specimens broke under tension near these explosive pockets of trapped air, these were under pressure in the cured composite. The spaces are distinguishable by a brownish mark and then any light brown mark discovered during machining has been treated as a suspicious space (although not visible to the naked eye). There appears to be more space than is considered desired, although the results of HCP (hydrostatic crush pressure) tests are acceptable. These foams were considered to have unsatisfactory properties under tension.
To address the problem with compressed gas spaces, the ingredients were mixed under various gases that were heavier than air. This is relatively easy to achieve as the only equipment required is a gas source, a flow meter and a short hose.
The gas must remain in the mixing vessel subject to currents and additional confinement. Mixtures that were mixed under airless atmospheres were then isostatically compressed in a pressure chamber similar to the “mixtures in air” samples.
The following effects were observed using different gases: • mixing under CO2 produced a space-free foam, but an adverse reaction to the curing agent in the epoxy resin system was observed: the samples mixed under this gas were denser than expected, although they maintained a satisfactory HCP; • mixture mixed under 100% argon produced smaller spaces identifiable by smaller brown marks, again with satisfactory HCP; • a welding gas with 5% CO2, 2.5% O2 by volume and the remaining argon was tested.
So far the results have been a space-free foam with no significant increase in density.
From the above mixtures under various gases, it appears that CO2 in small concentrations can slow the curing of the epoxy resin (not for large concentrations) and / or can change the surface tension of the liquid epoxy sufficiently to allow more gas (or gas exchange) faster) is absorbed into the epoxy resin before it hardens. During these tests, it was found that delayed post-cure temperature adjustment also reduced the spaces. This is believed to provide more time for the gas to be absorbed before the epoxy resin is fully cured.
Thus, the present invention incorporates the use of a gas to alter the properties and / or curing of an epoxy resin in order to help absorb the entrained gas in a mixture which is then placed under isostatic pressure until complete curing.
Figure 1 summarizes a suitable process according to the present invention, as previously described.
Figure 2 shows electron micrographs of polished broken sections of the composite. In the broken section (Figure 2a), spaces can be observed where the microspheres are extracted during the rupture.
Figure 3 shows a representative temperature profile during the high pressure steps of the process described here. A slight initial increase in temperature may be due to a slight curing exotherm, however, in the absence of external heating, the temperature remains largely constant at around 22-25 ° C. After about 6 hours, external heating is started, and about 5 to 6 hours it is required to reach a final temperature of around 80 ° C. Fluctuations in temperature can occur due to variations in the bath temperature due to the "variation" of the thermostat, and / or due to other causes, such as instability due to the curing exotherm. After about 6 hours of curing at high temperature, the composite is allowed to cool to about 30 ° C, this takes about 4 hours. At that point, the cured composite is ready for decompression.
Selection of hollow glass microspheres
Hollow glass microspheres can be obtained commercially from any manufacturer. Microspheres made by 3M ™ have been found to be particularly suitable. 3M uses the term 'glass bubbles' for hollow glass microspheres. Figure 5 shows a graph representing the available 3M glass bubbles showing HCP (crushing hydrostatic pressure) against the actual bubble density. From Figure 5 it is evident that the increase in HCP is due to the increased density - the correlation is approximately linear up to HCP of about 80MPa, although above that it seems possible to increase HCP without the substantial increase in density. The ideal microsphere for deep water applications could be found in the lower right part of the graph (low density / high HCP), however, these products are currently commercially unavailable. The table below provides the data in Figure 5 together with the identification of the particular degrees of tested microsphere.
10 From Figure 5 and the table above, it appears that the most efficient glass bubbles are K1 for low pressure applications, XLD3000 and XLD6000 for slightly higher pressure applications, and IM30K for extreme pressure applications. Although ÍM30K is not specifically manufactured for use in the manufacture of syntactic foam, it is nevertheless an efficient glass bubble for use in this application. A 5 glass (possibly custom-made) bubble material of 0.4 g / cc density and about 12,000 psi (about 83MPa), the crush strength from Figure 5 appears to be adequate. Glass bubbles XLD6000, IM30K and S42XHS were selected for testing.
Selection of a suitable epoxy resin system 10 Pure specimens of the following types of epoxy resin were tested for density and compressive strength; • KINETIXOR118 ATL Composites R118 epoxy with H103 curing agent • KINETIXOR246 ATL Composites R246 epoxy with H128 curing agent • KINETIXOR240 ATL Composites R240 epoxy with H341 curing agent • Epiglass®HT9000 Epiglass®HT9000 StandardHydronH0009000H2x900H210H210 standard L285 epoxy with curing agent L285 • 862L6 Hexion Chemicals Epon® 862 with curing agent Lindau Lindride®6 • 862LS-8IK Hexion Chemicals Epon® 862 with curing agent Lindau Lindride®6
The stress-strain curves under compression are shown in Figure 4. Thus, Figure 4 illustrates the properties of various epoxy resins that have been cured under high pressure. Figure 4a shows the compressive stress-strain curves, indicating that the materials are capable of withstanding a compressive stress of more than 80MPa, and in one case, more than 120MPa. Figure 4b shows the modulus values derived from the curves in Figure 4a. The initial modulus is between about 3 and 4GPa, however it is reduced when the deformation is more than about 2% (corresponding to the stress of about 60-80MPa). From these values it appears that the region in which these materials are reasonably elastic is up to at least about 2% deformation. Figure 4c shows the Poisson's ratio corresponding to the curves of Figures 4a and 4b. The Poisson's ratio is observed to increase approximately linearly to at least about 4%, and the linearity of the Poisson's ratio appears to increase with the reduction of the maximum stress rating.
The following densities were measured: • R118 1,130 g / cc • R246 1,136 g / cc • R240 1,185 g / cc • HT9000 1,166 g / cc • L285 1,172 g / cc • 862L6 1,235 g / cc • 862LS-81K 1,217 g / cc Specimen production
In a representative process. The recommended ratio of epoxy resin and curing agent was mixed with glass microspheres to obtain a microsphere concentration of about 66-67% by volume in the mixture. The mixture was conducted under a flux of solder gas comprising 2% oxygen, 5% carbon dioxide and 93% argon for a sufficient time to obtain a homogeneous mixture of a paste-like consistency. The mixture was wrapped in a flexible plastic film and immersed in liquid at room temperature. A pressure of about 1500psi (about 10,300kPa) was applied to the liquid to pressurize the mixture. The pressure was maintained for about 15 hours and the temperature then increased (while maintaining the same pressure) at about 80 ° C. That temperature and pressure were maintained for about 8 hours, after which the resulting cured composite was cooled to about room temperature before the pressure was released.
Although the increased compressive strength of an epoxy resin can increase the HCP of syntactic foam, the effect of increased epoxy resin strength when the HCP of the syntactic is above the compressive strength of the epoxy is not great. The disadvantage of the increased compressive strength of the epoxy resin is that it generally coincides with the increased epoxy resin density. The densities of the epoxy resins described above are within a range of less than 0.105 g / cc. Among the tested resins, the effect on syntactic buoyancy may be greater than 2lbs / cuft (0.032g / cc) in a glass bubble with high compaction densities. 10 Figure 6 shows a graph representing the HCP of syntactic foam and the density that was produced using different degrees of glass bubble at various densities of compaction with different epoxy resins. From these results, it appears that the density of glass bubble compaction and the different epoxy resins alter the density and HCP of syntactic foam, 15 but mainly the HCP of the glass bubble that determines the HCP of syntactic foam. The table below shows the data (HCP, density and tension (pε)) in Figure 6, which identifies the foams (by proportion of microspheres, nature of microspheres and nature of epoxy resin).

• XLD6000 - syntactic foam made with XLD6000 glass bubbles fulfilled the desired densities. The foams were made with MCP ranging from about 96MPa to 132MPa. Although very efficient for limited depth applications, these HCP values do not meet the FofS for the depth requirements required for very deep water applications. • S42XHS - unsightly syntactic foams with S42XHS glass bubbles did not meet the desired densities up to 0.024g / cc. This makes them even less efficient than revealed. However, a foam specimen was made with 151MPa HCP at a density of 0.67g / cc. While FofS in these surroundings may be acceptable, its density is less than desired. • ÍM30K - a specimen of syntactic foam made with ÍM30K glass bubbles has a generally acceptable density. It also resists the highest compaction density of all other mixtures. Despite having an exceptionally high HCP (206.8MPa), this one is too heavy for the application of general buoyancy. However, it can be useful in other areas of an underwater vehicle that requires a lightweight material with exceptional strength.
With reference to Figure 6 and the associated table, a degree of glass bubble between XLD6000 and IM30K appears to be preferred. Situated in a straight line between these two products, "low target" could be a 10,000 psi (68.9MPa) HCP glass bubble at 0.35g / cc density, while "high target" could be a HCP bubble of 16,000psi (110.3MPa) at 0.425 g / cc density. It was contemplated that using these microspheres, not only would FofS be satisfied in HCP, but a light material with buoyancy for any deep application could be produced. Even a single degree between these targets could help fill a gap to allow manufacturers of syntactic foam to meet the needs of the customer who demands more efficient, high-strength foams.
Figure 7 shows the behavior of a composite prepared using IM30K glass microspheres together with S42XHS glass microspheres under hydrostatic pressure. The ÍM30K microspheres provide increased resistance while the S42XSH microspheres provide reduced density. The extensometers were attached to the upper and lower part of the sample. It can be seen that there is very little difference between the curves, this indicates a substantially symmetrical compression performance and consequently the sample is substantially homogeneous. The compression performance shows a linear change in strain with a pressure increase of up to 160MPa, well above the design requirements for materials that will be used in deep water applications.
Figure 8 shows the compression tests of the sample used in Figure 7. Thus, Figure 8a shows a stress-strain curve under compression, indicating a largely linear behavior of up to about 100MPa / 1.5% deformation, with performance up to about 110Mpa / 2% deformation. Figure 8b shows the module performance. Even at about 2%, the module is above SGPa, and up to almost 1% it remains above 7GPa. Figure 8c shows the behavior of the Poisson's ratio. This increases approximately linearly, but even at about 2% deformation it is only about 0.4.
Figure 9 shows a fragment of the actual composite sample used in Figure 8 after the compressive failure. It can be seen that the sample does not show visible spaces. As previously noted, spaces in the cured composite can act as sample failure initiation sites, resulting in reduced final compressive strength.
Figure 10 shows the results of flexion testing of a sample made using 10% IM30K glass microspheres and 57% S42XHS glass microspheres with R118 / H103 epoxy resin. Figure 11 shows a sample after the fracture, indicating a total rupture. It can be seen that the samples can withstand a bending force of up to about 24kN. The curves are linear, indicating that throughout the test range, the material behaves elastically in flexion mode. The fact that the compressive strains (the curves that slope downwards to the right) have values almost similar to those under tension (those that slope upwards to the right) is stimulating, since this indicates that the material behaves similarly under compression and voltage. The sample used in this test was made using lower pressure and other specimens made using higher pressure produced better results in flexion mode.
To test the curability of the curable mixture before curing, a batch of curable mixture comprising 10% IM30K glass microspheres, 57% S42XHS glass microspheres with R118 / H103 epoxy mixture at 20 ° C was formed in a cylindrical shape approximately 110mm in diameter by 380mm in length. 31.2 kg must be added to a flat plate 5 to make the same pancake (for a few minutes). The slaughter rate is minimal after that period. The width of the flattened cylinder has been reduced by about 85 mm. The contact area of the flat plate on the mixture has an oval shape approximately 110mm wide x 390mm long. It is estimated that it has an area of approximately 10 33.150mm2 with a force of 0.306kN, which refers to 9.227kPa. Test protocols
The following test protocols were used in the experiments described above:
Pressure test: 15 A 100mm x 100mm x 100mm sample was used as a sample and extensometers centrally positioned on four faces or on two opposite faces. For a hysteresis test, the pressure was increased from 0 to 125MPa and back, cycle 5 times. The elevation rate is 10MPa / minute. After the cycle, the sample was increased to failure. For the failure test, the 2nd pressure at the beginning of the failure was recorded. Bending test at 4 points:
The apparatus is as shown in Figure 12. Three parallel 120 ° notches were made centrally in the sample as shown in Figure 12. The cylinders used are 20mm in diameter and 75mm in length. The 25 0790 ° extensometers were centrally positioned and 10mm separated and duplicated at the bottom of the sample, or alternatively a 0790 ° strainer was centrally positioned at the top and bottom. The force was increased until the sample failed.
A 4-point bending test was considered preferred for testing the materials present. The generally used 3-point bending test does not necessarily result in rupture at the weakest point in the specimen. A 4-point flexion test was therefore adopted since it allowed the defective specimen to break at a point of weakness. applications
The present invention was developed for use as a structural component in regions of very high pressure as well as in deep waters. However, other applications where the epoxy of the invention can find application include capstan winches in yachts, in loudspeaker cones, as protection against explosions and in cylinders and pistons.

权利要求:
Claims (14)
[0001]
1. Epoxy composite, characterized by the fact that it comprises a particulate load and has a final stress under compression greater than or equal to 10OMPa and a density less than 0.7 g / cm3 and an equilibrium water absorption less than 0.5 % w / w measured at a pressure of 10OMpa and at a temperature of 20 ° C or 25 ° C, where% w / w refers to the percentage increase in weight, according to the formula: Water absorption percentage = [(weight liquid - dry weight) / dry weight] x 100.
[0002]
2. Epoxy composite according to claim 1, characterized by the fact that it exhibits linear distortion less than or equal to 0.9% under hydrostatic compression pressure of HOMPa.
[0003]
Epoxy composite according to any one of claims 1 to 2, characterized by the fact that the particulate charge consists of hollow microspheres.
[0004]
4. Epoxy composite according to any one of claims 1 to 3, characterized by the fact that the particulate charge is present in the composite at 60% or more by volume.
[0005]
Epoxy composite according to any one of claims 1 to 4, characterized in that it additionally comprises a second filler.
[0006]
Process for the manufacture of an epoxy composite according to claim 1, the process characterized by the fact that it comprises: combining an epoxy prepolymer, a curing agent and a particulate filler to form a curable mixture; stirring the mixture under an airless atmosphere to make it substantially homogeneous, the atmosphere having a solubility in the curable mixture that is greater than the solubility of air in the curable mixture at the same temperature; apply pressure to the mixture to reduce or eliminate gas pockets in the mixture; and maintaining pressure until the curable mixture is cured to form the epoxy composite.
[0007]
Process according to claim 6, characterized in that the prepolymer and the curing agent are such that the working time of the curable mixture at 20 ° C is at least 1 hour.
[0008]
Process according to any one of claims 6 to 7, characterized in that the step of applying pressure is conducted so that the mixture is not exposed to air or the airless atmosphere.
[0009]
9. Process according to any of claims 6 to 8, characterized by the fact that the particulate charge consists of hollow microspheres.
[0010]
Process according to any one of claims 6 to 9, characterized in that it comprises heating the curable mixture to initiate or accelerate the curing to form the epoxy composite.
[0011]
11. Process according to claim 10, characterized by the fact that the heating starts in a time, referred to here as delay time, after the start of applying pressure to the mixture, optionally in a time of at least 1 hour after the start.
[0012]
12. Process according to any one of claims 10 to 11, characterized by the fact that the epoxy composite is cooled before the pressure is released.
[0013]
13. Use of an epoxy composite according to any one of claims 1 to 5, characterized by the fact that it presents itself as a structural component under compression.
[0014]
14. Use, according to claim 13, characterized by the fact that the use is made in a device for use under water.

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同族专利:

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公开号 | 公开日

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AU2011269656A1|2013-01-24|

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CA2803640C|2018-07-31|

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MY168652A|2018-11-28|

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ES2675343T3|2018-07-10|

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MX2012015132A|2013-05-09|

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EP2585534A1|2013-05-01|

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BR112012033203A2|2016-11-16|

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CA2803640A1|2011-12-29|

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RU2013102969A|2014-07-27|

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EP2585534A4|2015-03-11|

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CN103154129B|2016-05-25|

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TR201809277T4|2018-07-23|

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AU2011269656B2|2015-03-26|

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IL223738A|2017-06-29|

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JP5934197B2|2016-06-15|

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JP2013529691A|2013-07-22|

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US9267018B2|2016-02-23|

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US20130172448A1|2013-07-04|

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MX341153B|2016-08-09|

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WO2011160183A1|2011-12-29|

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SG186413A1|2013-01-30|

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EP2585534B1|2018-04-04|

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CN103154129A|2013-06-12|

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法律状态:
2018-04-10| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-10-22| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-05-26| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2020-10-27| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 23/06/2011, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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AU2010902788|2010-06-24|

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AU2010902788A|AU2010902788A0|2010-06-24|Epoxy composite|

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PCT/AU2011/000772|WO2011160183A1|2010-06-24|2011-06-23|Epoxy composite|

---