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    • 专利摘要:
    Resins reinforced with graphene nanoparticles or with a combination of graphene nanoparticles and carbon nanotubes. The present invention provides resins reinforced with graphene nanoparticles (gnp) or with a combination of gnp and carbon nanotubes (cnt). It also provides methods for obtaining said reinforced resins, by dispersion of gnp or a combination of gnp and cnt in a resin, and its use in modifying the properties of different substrates. The use of reinforced resins directly as an integral part of substrates or their use as a coating allows to avoid the formation of ice or to cause its release, and to obtain a greater resistance to deterioration in the face of adverse atmospheric conditions. The present invention also describes methods for curing said resins, repairing substrates containing them and methods for adhering two substrates based on the properties that the reinforcement with gnp or with a combination of gnp and cnt confers on said resins. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2644347A1
    申请号:ES201630692
    申请日:2016-05-27
    公开日:2017-11-28
    发明作者:Silvia GONZALEZ PROLONGO；Rocio MORICHE TIRADO；Maria SANCHEZ MARTINEZ；Alberto JIMENEZ SUAREZ；Alberto DEL ROSARIO HERNANDEZ；Alejandro Ureña Fernandez
    申请人:Universidad Rey Juan Carlos；
    IPC主号:
    专利说明:

    DESCRIPTION

    Resins reinforced with graphene nanoparticles or with a combination of graphene nanoparticles and carbon nanotubes.
     5
    FIELD OF THE INVENTION
    The present invention describes resins reinforced with graphene nanoparticles (GNP), or with a combination of graphene nanoparticles (GNP) and carbon nanotubes (CNT). The resins of the present invention are used to obtain materials, paints or coatings that prevent the formation or cause the release of ice formed in various substrates. The present invention also describes methods of curing said resins, repairing substrates containing them and methods for adhering two substrates based on the properties that reinforcement with GNP or with a combination of GNP and CNT confers on said resins and substrates that they contain them or which they cover. fifteen

    BACKGROUND OF THE INVENTION
    The formation of ice is a problem that affects various fields such as aeronautics, wind energy, photovoltaics and oil plants, among others [C. Antonini et al. Cold Regions Science and Technology 67: 58-67, 2011]. The formation of ice on the blades of a wind turbine not only affects its aerodynamics, which causes decreases of up to 50% in annual energy production, but can cause mechanical and electrical failures [M. Susoff et al. Applied Surface Science 282: 870-879, 2013]. This necessitates the implementation of methods that prevent the formation or cause the detachment of the ice formed. 25
    It is known in the state of the art the use of hydrophobic or superhydrophobic coatings for antifreeze applications that prevent its formation by not allowing water to wet the surface [L. Oberli et al. Advances in Colloid and Interface Science 210: 47-57, 2014].
    Liquid substances with antifreeze or thaw properties are also known in the state of the art. These substances are widely used in the aviation industry, hence there are numerous patents that protect different
    Compositions of this type of products (US5759436, US 2004/0036054 A1, US 2003/0098438 A1 and US 2014/0042357).
    Several studies have appeared in recent years in which the addition of carbon nanotubes (CNT) in a polymer matrix is used to increase its electrical, mechanical and thermal properties. 5
    In these studies systems are used that include the addition of carbon nanotubes (CNT) to the polymer matrix so that, by resistive heating, thaw occurs [CN102460447 A]. In this case, the authors have used CNT incorporated or adhered to fibers or fiber composite materials that in turn are incorporated into resins. These materials manage to raise the temperature thanks to their good electrical conductivity, but their thermal conductivity is not high enough to distribute the generated heat homogeneously.
    The addition of graphene in polymeric matrices and sol-gel compositions has also been used to achieve homogeneous heating while maintaining the transparency of the matrix [US 2011/0297661 A1]. For this, the 15 thermal conductivity properties of graphene are used, but not their properties as an electrical conductor. Therefore, compositions are used in which heating of different materials is induced, but without the use of the Joule effect. That is, graphene is used in quantities that are not sufficient to have properties as an electrical conductor, or, if the quantities are sufficient for the resulting material to have conductive properties, its electrical insulation, including an additional material, is carried out. That is electrical insulator.
    CNTs have also been used to heat a structure by microwave or UV radiation, using electromagnetic induction or radiation, preferably with the use of infrared or microwave emitters [WO 2013172762 25 A1].
    In previous studies it has been proven that the addition of graphene nanoparticles (GNP) to a resin to obtain resins reinforced with GNP, produces an increase in the contact angle in water wettability tests, reaching values greater than 90º. These properties make GNP reinforced resins 30 hydrophobic materials. Likewise, when the addition of graphene nanoparticles (GNP) is carried out in concentrations higher than the threshold value of electric percolation, the resins reinforced with GNP are also electrical conductors and produce a Joule [S.G. Prolongo et al. European Polymer Journal 61: 206-214. 2014]. 35
    DESCRIPTION OF THE INVENTION
    The present invention relates to resins reinforced with graphene nanoparticles (GNP) or with a combination of GNP and carbon nanotubes (CNT), methods of obtaining these reinforced resins, and the use of said reinforced resins directly as an integral part of different substrates, or in coatings and paints for said substrates, for the modification of properties such as electrical and thermal conductivity in said substrates.
    Both GNPs and CNTs are nanoparticles, that is, they are nanometric particles of at least one dimension smaller than 100 nm.
    The nanoparticles that reinforce the resins of the present invention may be graphene nanoparticles (GNP) or a combination of graphene nanoparticles (GNP) and carbon nanotubes (CNT).
    The present invention utilizes both GNP reinforced resins and reinforced resins with a combination of GNP and CNT to make use of their electrical and thermal properties. fifteen
    Thus, resins reinforced with graphene nanoparticles (GNPs), or with a combination of GNP and carbon nanotubes (CNT) according to the present invention, possess superior thermal and electrical properties useful in various industrial applications as members of different substrates or as coatings or paints of said substrates. twenty
    In an embodiment of the present invention, said reinforced resins are directly part of a substrate in which it is necessary to prevent the formation of ice or cause the release of ice formed in said substrate.
    In another embodiment of the present invention, said reinforced resins are members of a paint or a coating that covers a substrate, in which it is necessary to prevent the formation of ice or cause the formation of ice formed; or are used to increase the resistance to deterioration against adverse atmospheric conditions in said substrates.
    The thermal and electrical properties of said reinforced resins of the present invention also make them useful in the repair of various substrates, or in methods for adhering two different substrates.
    The electrical and thermal properties that the reinforced resins of the present invention confer to the substrates of which they form part of their composition, or to
    those that cover, cause, when applied to them a voltage, a homogeneous increase in temperature.
    Said homogeneous increase in temperature generated by the reinforced resins of the present invention can also be produced in an auxiliary manner by a second route: through an efficient infrared energy receiving capacity from the sun.
    Graphene is an allotropic form of carbon that forms an atomic scale a two-dimensional structure of hexagonal cells of the "honeycomb" type. Graphene is present in highly varied research and application areas thanks to its high electrical conductivity, of the order of magnitude of 104 S / m in its main plane and its thermal conductivity close to 5000 W / m K.
    In this invention graphene nanoparticles (GNP) are defined as graphene structures in which graphene layers are stacked by Van der Waals force joints and have a size smaller than 100 nm. GNPs are, therefore, essentially two-dimensional structures with nanometric size. The main plane of graphene nanoparticles (GNP) is defined as the "honeycomb" structure growth plane.
    They are defined as carbon nanotubes (CNT) to the allotropic form of carbon that has cylindrical structures. They are, therefore, unlike graphene nanoparticles (GNP), monodimensional nanoparticles with nanometric size. twenty
    The reinforced resins according to the present invention are obtained by addition, from graphene nanoparticles (GNP) or a combination of graphene nanoparticles (GNP) and carbon nanotubes (CNT) by means of a dispersion process of said nanoparticles. Said resins are, therefore, resins reinforced with GNP or resins reinforced with a combination of GNP and CNT. 25
    The application of a voltage to the reinforced resins according to the present invention induces an increase in temperature by Joule effect.
    The Joule effect is defined as the heat generated in an electrical conductive material as a result of the circulation of electric current through it, which causes an increase in temperature in said material. 30
    The addition of graphene nanoparticles (GNP) or a combination of GNP and carbon nanotubes (CNT), induces an increase in electrical and thermal conductivity in resins. This increase in thermal conductivity is directly proportional to the content of GNP and CNT. No percolation effect is observed in
    thermal conductivity, since heat transport occurs through phonons. However, the electrical conductivity has a clear threshold percolation value, due to the need for electrical percolation in the nanoparticle network. The electrical percolation threshold value corresponds to a much lower concentration for CNTs than for GNPs (0.1% and 2% by weight, respectively), difference 5 due to the geometry of the nanoparticles (monodimensional in CNT and bidimensional in GNP) and the relationship of form.
    The critical percolation threshold value is defined as the critical concentration of GNP or CNT necessary for the formation of an interconnected network of said GNP and / or CNT through which electrons travel along the reinforced resin, and is characterized by a drastic increase in conductivity, attributed to the formation of said conductive network.
    The heating by Joule effect therefore depends on the electrical and thermal conductivities of the resins that are used, which, in turn, depend on the composition of nanoparticles used (amounts of GNP and CNT). The thermal conductivities 15 of the nanoparticles vary in ranges of 1 W / mK for amorphous carbon, to 5000 W / mK for a graphene monolayer. The thermal conductivity of multi-walled carbon nanotubes is close to 3000 W / mK at room temperature. In contrast to this, graphene nanoparticles have a very high "in-plane" thermal conductivity (values greater than 5000 W / mK) and a lower "out-of-plane" thermal conductivity (~ 2 W / mK). Both the electrical conductivity of the GNP in its main plane and of the CNT in the direction of the cylindrical axis are very high, reaching values of the order of magnitude of 10,000 S / m.
    It has also been found that both the electrical properties and the thermal properties of the reinforced resins according to the present invention, in which GNP or a combination of CNT and GNP have been dispersed, strongly depend on the geometry, size and shape ratio of the nanoparticles they contain. Thus, while the addition of CNT causes a higher temperature increase than the addition of GNP when applying a lower electrical voltage (due to the greater electrical conductivity of the CNT), the heating is more homogeneous by increasing the GNP content , due to the greater thermal conductivity of these. Therefore, the resins reinforced with GNP or with a combination of GNP and CNT according to the present invention, manage to use the superior thermal conductivity of the GNPs, when the GNPs are used exclusively, or the superior thermal conductivity of the GNPs together with the superior electrical conductivity of CNTs when using a combination of both. Reinforced resins are thus obtained that produce a
    more homogeneous Joule heating, which makes it possible to use these reinforced resins in industrial applications, such as preventing the formation of ice on a surface or causing it to detach.
    The reinforced resins according to the present invention thus contain GNP or a combination of GNP and CNT. The increase in temperature generated by said resins 5 by Joule effect makes them useful as an integral part of substrates, or as paint or coating thereof, when the prevention of the formation of ice or its detachment from the surface of said substrates is required.
    The increase in temperature that resins reinforced with GNP or with a combination of GNP and CNT generate materials within the scope of the present invention, both when they are an integral part of them, and when they are applied on them as paint or as a coating It is produced in two ways: (1) by applying a sufficient voltage to cause the required temperature increase or, (2) auxiliary, through an efficient capacity to receive infrared energy from the sun. fifteen
    Heating by the effect of solar energy (2) occurs because the substrate, paint or coating is obscured by the addition of graphene nanoparticles (GNP) increasing the amount of radiation absorbed. This heating mode is used as an auxiliary method to heating by Joule effect obtained by the application of a voltage. twenty
    The heating caused, together with the hydrophobic character due to the addition of graphene nanoparticles, decreases the deterioration caused by ice in a substrate comprising the reinforced resins according to the present invention.
    An embodiment of the present invention is the methods of obtaining resins reinforced with GNP or with a combination of GNP and CNT comprising:
    (i) dispersing an amount of graphene nanoparticles (GNP), or a combination of GNP and carbon nanotubes (CNT), in a mixture of monomers of a resin,
    (1) performing 1-10 calendering cycles;
    (2) maintaining the speed of each calendering cycle between 150 and 30,500 rpm; Y
    (3) reducing the separation between rollers in each calendering cycle between 150 and 2 µm.
    (ii) eliminate gases formed under vacuum,
    (iii) add a crosslinking compound, and
    (iv) cure the mixture obtained in (iii),
    and where the amount of GNP, or the combination of GNP and CNT, is at least sufficient to reach the threshold concentrations of electrical percolation of the GNP and the corresponding CNTs that integrate said resin.
    Crosslinking compounds of the present invention are compounds that cause polymerization, and in particular comprise aromatic amines.
    Resins of the present invention are thermosetting resins, in particular bicomponent epoxies.
    The use of calendering to obtain the reinforced resins of the present invention facilitates the dispersion of the nanoparticles and also causes an extension 10 of the GNP, thus achieving reinforced resins that have a greater electrical conductivity.
    An embodiment of the present invention is the method of obtaining GNP reinforced resins, in which in step (i) it comprises in (1) at least 3 calendering cycles, (2) maintaining the speed of the calendering cycles between 200 and 15 400 rpm and increasing the speed in each successive calendering cycle, and (3) reducing the separation between rollers in each calendering cycle between 120 and 15 µm.
    Another embodiment of the present invention is a method of obtaining resins reinforced with GNP or with a combination of GNP and CNT, in which step (ii) is carried out at a temperature between 50-90 ° C for at least 10 minutes. twenty
    Another embodiment of the present invention is a method of obtaining resins reinforced with GNP or with a combination of GNP and CNT, in which step (iv) is carried out in a conventional manner by increasing the temperature of the mixture obtained in step (iii ).
    An embodiment of the present invention is a method of obtaining resins 25 reinforced with GNP, or with a combination of GNP and CNT, in which step (iv) is performed by applying a voltage of 75 to 300V and increasing the temperature of the mixture obtained in step (iii).
    Another embodiment of the present invention is a method of obtaining resins reinforced with GNP or with a combination of GNP and CNT as described above, in which step (i) (2) the speed of the calendering cycles is maintained between 200 and 400 rpm, and said speed is increased in each successive calendering cycle.
    An embodiment of the present invention is a method of obtaining resins reinforced with GNP or with a combination of GNP and CNT in which step (i) comprises (1) 7 cycles of calendering, in (2) maintaining the speed of calendering cycles at 250 rpm and (3) reducing the separation between rollers in each calendering cycle between 150 and 5 µm. 5
    EXAMPLE 1 describes a method of obtaining reinforced resins according to the methods of the present invention with GNP contents of 1.5, 2, 3, 5 and 8% by weight respectively.
    As shown in the EXAMPLES section, the thermal conductivity of the reinforced resins according to the present invention increases proportionally with the addition of different types of nanoparticles (GNP and / or CNT). The use of these reinforced resins at high temperatures makes it important to determine the maximum temperature at which they can be used. This is done in EXAMPLE 2, where reinforced resins according to the present invention are characterized by Dynamic Mechanical Thermal Analysis (DMTA). fifteen
    The DMTA technique measures visco-elasticity as a function of temperature and determines the storage module of a resin by applying an oscillating force to said resin.
    Since the resins used in the present invention are thermosetting resins it is possible to associate the maximum operating temperature of said reinforced resins 20 according to the present invention with the glass transition temperature.
    It is defined as glass transition temperature (Tg) at that temperature at which the resins undergo a strong change in their physical and mechanical properties. Below said temperature the resin is in a vitreous state, but above that temperature Tg the resin passes into a rubbery or elastomeric state, with elastic properties.
    Table 1 of EXAMPLE 2 and the graphs in FIG. 1 show these values.
    The GNP reinforced resins according to the present invention have an elevated storage module at room temperature that decreases slightly with increasing temperature. The stiffness of said resins changes abruptly at 30 high temperatures, which is associated with α-relaxation from the storage state to the elastic state of said thermosetting resin. The addition of GNP or CNT to the resins causes an increase in the storage module at room temperature, but also causes a decrease in the glass transition temperature. The highest measured module corresponds to a reinforced resin 35
    with 8% by weight of GNP. The value reached is 42% higher than that of the resin without GNP. In the case of resins reinforced only with CNT, the module is only increased by 15% regardless of the amount of CNT added to the resin. This demonstrates the superiority of the thermomechanical properties of the reinforced resins according to the present invention since thanks to their GNP content they reach much higher storage module values.
    The storage module is associated with the energy stored in the material while the loss module is associated with the energy dissipated by the material. 10
    The section corresponding to EXAMPLE 3 shows the thermal conductivity of the reinforced resins according to the present invention. Specifically, FIG. 2 shows the variation in thermal conductivity due to the addition of different quantities of graphene nanoparticles (GNP) and carbon nanotubes (CNT) to the resins according to the present invention. The thermal conductivity increases proportionally with the amount of GNP or CNT added to the resin. The highest values are obtained by the resins reinforced with GNP according to the present invention.
    In contrast to thermal conductivity, electrical conductivity shows an electrical percolation threshold value. In addition, this is different depending on the nanoparticle used (FIG. 3, EXAMPLE 4). In the case of reinforced resins 20 exclusively with CNT, the threshold value of electric percolation is reached with concentrations close to 0.1% by weight, much lower than in resins reinforced with GNP according to the present invention, with values close to 2% in weigh.
    The reinforced resins according to the present invention use Joule effect to heat the material itself or the surface of substrates in which the formation of formed ice is required or to prevent its formation. The Joule effect on reinforced resins according to the present invention has been measured and has also been compared with the Joule effect obtained on resins reinforced exclusively with CNT (EXAMPLE 5). For this, in section 5.1 of EXAMPLE 5, the temperature has been measured as a function of the applied voltage (FIG. 4) and also the current intensity together with the temperature reached as a function of the applied voltage (FIG. 5).
    The results show that the increase in the concentration of nanoparticle dispersed in the resin induces an increase in the electric current for the same applied voltage (CNT in FIG 4a and GNP in FIG 4b) due to a higher conductivity.
    electric In addition, this increase in electric current also means a greater increase in the temperature reached due to the Joule effect. The results also show a dependence on the Joule effect with respect to the nanoparticle used (CNT or GNP). For the same electric current transported, the temperature reached is different for CNT or GNP reinforced resins. 5
    FIG. 5 shows a summary of the electrical conductivities of CNT reinforced resins or GNP reinforced resins according to the present invention and the maximum temperature reached as a function of the applied voltage. It can be verified that, at higher electrical conductivity, the temperature reached is higher with lower voltages supplied. 10
    The increase in the concentration of nanoparticles dispersed in the resin increases the electrical conductivity, which is observed by an increase in the electric current transported for the same voltage. This increase in the transported electric current translates into a greater increase in temperature due to the Joule effect.
    On the other hand, in FIG. 6 the homogeneity of the heating caused by Joule effect 15 is analyzed for both GNP reinforced resins according to the present invention, and for resins exclusively reinforced with CNT. For this, infrared thermography has been used.
    To explain the results obtained in FIG. 6, we must take into account the results shown in FIG. 4. Both the GNP reinforced resins according to the present invention, and the resins exclusively reinforced with CNT reach high temperatures close to 75 ° C, but the applied voltage is different. Resins reinforced with GNP according to the present invention require higher voltages than resins reinforced exclusively with CNT. However, in the GNP reinforced resins according to the present invention, the homogeneity of the heating is superior. Thus, when analyzing (FIG. 6) the resins exclusively reinforced with CNT present areas with different temperatures (represented by the greater or lesser darkness in the thermographic images), from 60 to 80 ° C, while the resins reinforced with GNP according to the present invention they have a homogeneous temperature throughout the studied area. 30
    Finally, in EXAMPLE 6 the reproducibility of the heating obtained by the reinforced resins according to the present invention for its industrial application has been analyzed. FIG 7 shows several heating cycles by Joule effect that are the result of applying the same voltage several times, for a short period of time, to resins exclusively reinforced with CNT (0.1% CNT in FIG. 7a) and to resins 35
    reinforced with GNP according to the present invention (10% GNP in FIG. 7b). The heating by Joule effect is reproducible since in all the cycles the same maximum temperature is obtained.
    It can be concluded that the use of GNP reinforced resins according to the present invention provides thermal properties superior to those currently available on the market in the materials that integrate them, and that the use of reinforced resins with a combination of GNP and CNT according to the present invention have thermal and electrical properties superior to the materials known in the state of the art.
    An embodiment of the present invention is a resin reinforced with a concentration of at least 7% by weight, obtainable according to the methods of the present invention.
    An embodiment of the present invention is a resin reinforced with a concentration of GNP comprised between 7 and 15% by weight, obtainable according to the methods of the present invention. fifteen
    Another embodiment is a resin reinforced with 8% GNP, obtainable according to the methods of the present invention.
    Another embodiment is a resin reinforced with 10% GNP, obtainable according to the methods of the present invention.
    An embodiment of the present invention are reinforced resins with a combination 20 of GNP and CNT characterized in that the concentrations of GNP and CNT are each above the threshold concentrations of electrical percolation of said corresponding GNP and CNT, integrating said reinforced resin.
    An embodiment of the present invention is a resin reinforced with at least 7% GNP and at least 0.05% CNT by weight. 25
    Another embodiment of the present invention is a resin reinforced with 8% GNP and 0.1% CNT by weight.
    Another embodiment of the present invention is a resin reinforced with 10% GNP and 0.1% CNT by weight.
    An embodiment of the present invention is a material characterized in that it comprises a resin reinforced with GNP or with a combination of GNP and CNT described in the previous embodiments.
    An embodiment of the present invention is a material according to any of the embodiments described above, characterized in that said material is a paint.
    An embodiment of the present invention is a material according to any of the embodiments described above in the present invention, characterized in that said material is a coating.
    For the purposes of the present invention, coating is defined as a material that covers the surface of another material for protection or to improve its appearance and / or physical properties.
    An embodiment of the present invention is a method of preventing the formation of ice 10 or of releasing the ice formed on a substrate or on the surface of a substrate comprising, respectively,
    - including in the composition of said substrate a reinforced resin, or a material comprising said reinforced resins, according to the embodiments described above; or 15
    - coating the surface of the substrate with a reinforced resin according to the present invention, a paint or coating comprising said reinforced resins according to the embodiments described above, and
    applying on said substrate, or on the surface of said substrate, a voltage that generates an increase in temperature by Joule effect on the substrate, or on the surface of the substrate, sufficient to prevent ice formation or release the ice formed in said substrate or on the surface of said substrate.
    In another embodiment of the present invention the method of preventing the formation of ice or of releasing the formed ice described above, is characterized in that the voltage applied on said substrate, or on the surface of said substrate is between 75 and 300 V.
    Another embodiment of the present invention is the method of preventing the formation of ice or of releasing the formed ice described above, where said substrate or the surface of said substrate is also exposed to the sun.
    An embodiment of the present invention is a method of repairing a substrate or the surface of a substrate comprising,
    (i) dispersing an amount of GNP or a combination of GNP and CNT in a mixture of monomers of a resin,
    (1) performing 1 to 10 calendering cycles,
    (2) maintaining the speed in each calendering cycle between 150 and 500 rpm, and
    (3) reducing the separation between rollers in each calendering cycle between 150 and 2 µm;
    (ii) eliminate gases formed under vacuum; 5
    (iii) add a crosslinking compound;
    (iv) add the mixture obtained in step (iii) on the substrate or on the surface of the substrate to be repaired, and
    (v) curing the mixture obtained in step (iii), applying a voltage between 75 and 300V and increasing the temperature on the substrate or on the surface 10 of the substrate.
    The amount of GNP, or the amount of a combination of GNP and CNT, used in said embodiment results, respectively, in concentrations by weight of the mixture obtained in step (iii) greater than the threshold concentrations of electric percolation of said GNP and CNT, and are therefore sufficient to generate a heating by Joule effect by applying a voltage on said resins or on the substrates and / or materials in which they are integrated.
    More preferably, the amounts of GNP and CNT used in the method of repairing a substrate or the surface of a substrate as described above, result in concentrations of between 1.5 and 15% by weight GNP and between 20 0.01 and 0.5% in CNT weight, and in any case they are above those necessary to exceed the electric percolation threshold concentrations.
    An embodiment of the present invention is a method of repairing a substrate or the surface of a substrate as described above, characterized by (i) dispersing an amount of GNP, or a combination of GNP and CNT resulting in a concentration of at least 7% GNP, or at least 7% by weight of GNP and at least 0.05% by weight of CNT in the mixture obtained in step (iii).
    Another embodiment of the present invention is a method of adhering a substrate A to a substrate B comprising:
    (i) dispersing an amount of GNP or a combination of GNP and CNT in a mixture of monomers of a resin
    (1) performing 1 to 10 calendering cycles and
    (2) maintaining the speed in each cycle of calendering between 150 and 500 rpm;
    (3) reducing the separation between rollers in each calendering cycle between 150 and 2 µm;
    (ii) eliminate gases formed under vacuum; 5
    (iii) add a stoichiometric amount of a hardener compound;
    (iv) add the mixture obtained in (iii) on a surface of the substrate A;
    (v) contacting the surface of the substrate A of step (iv) with a surface of the substrate B and
    (vi) apply a voltage between 75 and 10 300 V on any of the contact surfaces and increase the temperature to cause the mixture obtained in step (iii) to cure and the adhesion of the contact surfaces of the substrate A and of substrate B respectively; and where the amount of GNP, or the amounts of GNP and CNT used, results, respectively, in concentrations by weight of the mixture obtained in step (iii) above the electrical percolation threshold concentrations of said GNP and CNT
    More preferably, the amounts of GNP and CNT used in the method to adhere a substrate A to a substrate B described above, result in concentrations of between 1.5 and 15% by weight GNP and between 0.01 and 0.5% by weight of CNT, and in In any case, they are above those necessary to exceed the 20 concentrations of electric percolation threshold.
    An embodiment of the present invention is a method for adhering a substrate A to a substrate B as described above, characterized by (i) dispersing an amount of GNP, or a combination of GNP and CNT resulting in a concentration of at least 7% of GNP, or at least 7% by weight of GNP and at least 0.05% by weight of 25 CNT of the mixture obtained in step (iii).
    One embodiment is the use of resins reinforced with GNP or with a combination of GNP and CNT according to the present invention for the manufacture of paints.
    Another embodiment is the use of resins reinforced with GNP or with a combination of GNP and CNT according to the present invention for the manufacture of coatings. 30
    Another embodiment is the use of reinforced resins according to the present invention for the protection of materials against adverse atmospheric conditions.
    Within the scope of the present invention, they are defined as adverse atmospheric conditions, such as those that cause a frost and, therefore, in which the formation of ice occurs on a surface of a material exposed to said adverse atmospheric conditions.
     5
    BRIEF DESCRIPTION OF THE FIGURES
    FIG. 1: Storage and loss modules in reinforced resins with different concentrations of CNT (1a) or GNP (1b) depending on the temperature.

    FIG. 2: Thermal conductivity values in resins reinforced with GNP according to the present invention and in resins reinforced exclusively with CNT.

    FIG. 3: Electrical conductivity curves in resins reinforced with GNP according to the present invention and in resins reinforced exclusively with CNT.
     fifteen
    FIG. 4: Measurement of the electric current and the associated temperature increase as a function of the voltage applied in resins exclusively reinforced with CNT (4a) and in resins reinforced with GNP according to the present invention (4b).

    FIG. 5: Electrical conductivity values of resins exclusively reinforced with 20 CNT (5a) and in resins reinforced with GNP according to the present invention (5b) together with the temperature reached as a function of the applied voltage.

    FIG. 6: Infrared thermography images of resins reinforced exclusively with 0.25% CNT (6a) and of resins reinforced with 8% GNP according to the present invention (6b).

    FIG. 7: Cyclic experiences of heating by Joule effect applying 50V for 30 min in resins reinforced with 0.5% CNT (7a) and with 10% GNP according to the present invention (7b). 30


    EXAMPLES

    EXAMPLE 1: Method of obtaining
    Graphene supplied by XG Science, under the trademark M25, has been used with a purity> 99.5% by weight, consisting of nanoparticles with an average thickness 5 of 6-8 nm laterally and an average size of 25 µm.
    An epoxy resin with the basic DGEBA monomer (Araldite LY556, bisphenol A diglycidyl ether) and an aromatic amine-type hardening compound (Araldite XB3473, mixture of diethyltholuenediamine and 1,2-diaminocyclohexane), both of Huntsman, have been used. 10
    The dispersion procedure consists of 7 calendering cycles with different rollers spaced between 15 and 5 µm and increasing the speed in each cycle: 250, 300 and 350 rpm. The dispersion was carried out in the monomer mixture of the resin. Once the dispersion is complete, the gases are removed from the mixture under vacuum conditions (40 mbar) at 80 ° C for 15 minutes. Subsequently, the hardener is added in a 100: 23 ratio (LY556: XB3473) by weight to achieve the stoichiometric ratio. The resin is cured at 140 ° C for 8 hours.
    The percentage of graphene nanoparticles (GNP) was determined based on the percolation threshold value.
    GNP reinforced resins with 1.5, 2, 3, 5 and 8% by weight of 20 graphene nanoparticles (GNP) were obtained.

    EXAMPLE 2: Characterization by DMTA
    DMTA (Dynamic Mechanical Thermal Analysis) measurements of samples of CNT-reinforced resins and GNP-reinforced resins according to the present invention were performed, using the simple cantilever beam flex mode in a DMTA V Rheometric Scientific apparatus. The measurements were made at 1 Hz, in a temperature range of 30 to 220 ° C, at a heating rate of 2 ° C per minute. The dimensions of the samples were 35x12x1.5 mm3. The storage module (E ’), the loss module (E’ ’) and the loss tangent (Tan Delta) 30 were measured as a function of temperature.
    In the following Table 1 and in the graphs of FIG. 1 these values are collected.
    Thermal diffusivity is equal to thermal conductivity divided by density and specific heat capacity at constant pressure. Thermal diffusivity measures the ability of a material to conduct thermal energy in relation to its ability to store it.
    To calculate the thermal conductivity, the specific heat capacity was determined by calorimetry using Differential Scanning Calorimetry (DSC, Mettler Toledo mod. 822e) while the density of the resins reinforced with CNT or GNP was measured with a Mettler Toledo balance (± 0.001 mg), equipped with a density measurement kit.
    FIG. 2 shows the variation of thermal conductivities for reinforced resins 10 with different amounts of GNP according to the present invention and for reinforced resins with different amounts of CNT. The thermal conductivity increases proportionally with the amount of GNP or CNT dispersed in the resin. The highest values are obtained by the GNP reinforced resins of the present invention. fifteen

    EXAMPLE 4: Measurement of electrical conductivity.
    The measurement of electrical conductivity compares the electrical properties of resins exclusively reinforced with CNT and of resins reinforced with GNP according to the present invention. twenty
    The measurement of the electrical conductivity was carried out following the ASTM D257 standard. For this, a Source-Meter Unit device (Keithley 2410 from Keithley Instruments) was connected through a GPIB interface to a PC. The electrical resistance was determined by Ohm's law by calculating the slope of the current-voltage intensity curve, from which the electrical conductivity can be determined taking into account the geometry of the samples used (10x10x1 mm3).
    In contrast to thermal conductivity, electrical conductivity shows an electrical percolation threshold value. In addition, the value is different depending on the nanoparticle used (FIG. 3). Thus, the concentration of nanoparticles dispersed in the resin that is required to reach the threshold value of electric percolation is different for cases in which CNT or GNP is added to the resin. In the case of dispersion exclusively of CNT, the threshold value of electric percolation is reached with values close to 0.1% by weight, much lower than resins reinforced with GNP according to the present invention, which requires values close to 2% by weight.
    EXAMPLE 5: Determination of the Joule effect

    5.1.- Temperature measurement depending on the electrical conductivity.
    For the study of Joule effect heating of the nanocomposites of the present invention, the Source-Meter Unit apparatus (Keithley 2410 of 5 Keithley Instruments) was used together with an IR laser digital thermometer. Different experiments were carried out to analyze various parameters such as the temperature increase depending on the electric current used (FIG. 4). Resins reinforced with GNP according to the present invention and resins reinforced exclusively with CNT were used. In all cases the electric current increases linearly with the applied voltage, 10 indicating that in all the cases studied Ohm's law is fulfilled. The results show that the increase in the amount of nanoparticle used (CNT in 4a and GNP in 4b) induces an increase in electrical current for the same voltage applied due to the greater electrical conductivity. In addition, this increase in electric current also means a greater increase in the temperature reached due to the Joule effect.
    The results also show a dependence with the nanoparticle used (CNT or GNP). For the same electric current carried, the temperature reached is different in resins reinforced exclusively with CNT than in resins reinforced with GNP according to the present invention. twenty
    FIG. 5 shows a summary of the electrical conductivities of resins exclusively reinforced with CNT or resins reinforced with GNP according to the present invention and the maximum temperature reached as a function of the applied voltage. It can be verified that, at higher electrical conductivity, the temperature reached is higher with lower voltages supplied. 25
    The increase in the concentration of the nanoparticle dispersed in the resin increases the electrical conductivity, which is observed by an increase in the electric current transported for the same voltage. This increase in the transported electric current translates into a greater increase in temperature due to the Joule effect.
     30
    5.2.- Measurement of heating homogeneity by Joule effect
    To analyze the homogeneity of heating by Joule effect, GNP reinforced resins according to the present invention have been studied by thermography against resins exclusively reinforced with CNT.
    Taking into account the results of the thermographic images shown in FIG. 6 the homogeneity of heating is superior in the GNP reinforced resins according to the present invention. The temperature reached is shown based on the shading intensity of the thermographic image. Thus, the whitish zones correspond to high temperatures, close to 80ºC and the darkest zones 5 correspond to lower temperatures. The resin reinforced exclusively with CNT (6a) presents important differences in the shading of the image, with zones that vary between 60 and 80ºC. In contrast to this situation, the GNP reinforced resin according to the present invention (6b) presents an image with less variations in shading intensity, that is, it has a homogeneous temperature due to its greater thermal conductivity. The lower thermal conductivity of the resins reinforced exclusively with CNT induces the appearance of areas with different temperatures.

    EXAMPLE 6: Reproducibility of heating by Joule 15 effect
    50V voltages for 30 minutes were applied to GNP reinforced resins according to the present invention, with a 0.5% by weight CNT content (7a) and a 10% GNP content (7b). After 30 minutes, the current is removed for 5 minutes. In both figures we observe that the heating is reproducible since the resins reinforced with the different nanoparticles reach the same maximum temperature in each cycle.
    权利要求:
    Claims (28)
    [1]

    1. Process for obtaining a resin reinforced with graphene nanoparticles (GNP) or with a combination of GNP and carbon nanotubes (CNT) comprising:
    (i) dispersing an amount of GNP, or a combination of GNP and CNT, in a mixture of monomers of a resin,
    (1) performing between 1 to 10 calendering cycles;
    (2) maintaining the speed of the calendering cycles between 150 and 500 rpm; and 10
    (3) reducing the separation between rollers in each calendering cycle between 150 and 2 µm;
    (ii) eliminate gases formed under vacuum,
    (iii) add a crosslinking compound, and
    (iv) cure the mixture obtained in (iii), 15
    and where the amount of GNP, or of the combination of GNP and CNT, is at least sufficient to reach the threshold concentrations of electric percolation of the GNP and the corresponding CNT, members of the reinforced resin.
    [2]
    2. The method of obtaining according to claim 1, characterized in that in stage (i) GNP is dispersed and that it comprises in (1) at least 3 cycles of calendering, (2) maintaining the speed of the calendering cycles between 200 and 400 rpm, and (3) reducing the separation between rollers in each calendering cycle in the range of 120 to 15 µm.
    [3]
    3. The method of obtaining according to any one of claims 1 or 2, wherein step (ii) is carried out at a temperature between 50 and 90 ° C for at least 10 min.
    [4]
    4. The method of obtaining according to any of claims 1-3, wherein step (iv) is performed by applying a voltage of 75 to 300 V and increasing the temperature of the mixture obtained in step (iii).
    [5]
    5. The method of obtaining according to any of claims 1-4, characterized in that the reinforced resin obtained is a thermosetting epoxy resin.

    [6]
    6. The process for obtaining according to any of claims 1-5, characterized in that the crosslinking compound is an aromatic amine.
    [7]
    7. The method of obtaining according to any of claims 1-6, characterized in that in step (i) (2) the speed of the calendering cycles is maintained between 200 and 400 rpm and said speed is increased in each cycle of 5 successive calendering.
    [8]
    8. The method of obtaining according to any of claims 1-6, characterized in that in step (i) it comprises (1) 7 calendering cycles, (2) maintaining the speed of the calendering cycles at 250 rpm and (3) reducing the separation between rollers in each cycle of calendering between 150 and 5 µm. 10
    [9]
    9. GNP reinforced resin obtainable according to the method of any of claims 1-8, characterized in that the concentration of GNP is at least 7% by weight of the resin.
    [10]
    10. A GNP reinforced resin obtainable according to claim 9, characterized in that the concentration of GNP is between 7 and 15% by weight of the resin.
    [11]
    11. Reinforced resin with a combination of GNP and CNT obtainable according to the procedure of any of claims 1-8, characterized in that the concentration of GNP and CNT is at least 7 and 0.05% by weight of the resin respectively. twenty
    [12]
    12. Reinforced resin with a combination of GNP and CNT characterized in that the concentrations of GNP and CNT are above the threshold concentrations of electrical percolation of the GNP and the corresponding CNT, integral of the reinforced resin.
    [13]
    13. Reinforced resin according to any of claims 11 or 12 characterized in that it comprises 8% GNP and 0.1% CNT by weight.
    [14]
    14. Reinforced resin according to any of claims 11 or 12 characterized in that it comprises 10% GNP and 0.1% CNT by weight.
    [15]
    15. Material characterized in that it comprises a reinforced resin according to claims 9-14. 30
    [16]
    16. The material of claim 15 characterized in that it is a paint.
    [17]
    17. The material of claim 15 characterized in that it is a coating.

    [18]
    18. Method for preventing the formation of ice or for releasing the ice formed on a substrate or on a surface of a substrate, comprising, respectively,
    - including in the composition of said substrate a reinforced resin according to claims 9 to 14, or a material according to claims 15 to 17; or
    - coating the surface of the substrate with a resin according to claims 9 5 to 14 or with a material according to claims 15 to 17, and
    apply on the substrate or on the surface of said substrate a voltage that generates an increase in temperature by Joule effect, on the substrate or on the surface of the substrate, sufficient to prevent the formation of ice or release the ice formed on said substrate or on the surface of said substrate. 10
    [19]
    19. The method of preventing the formation of ice or of releasing the ice formed of claim 18, characterized in that the substrate, or the surface of the substrate, is also exposed to the sun.
    [20]
    20. The method for preventing the formation of ice or of releasing the ice formed on a substrate or on the surface of a substrate, according to any of the 15 claims 18 or 19, characterized in that the applied voltage is between 75 and 300 V.
    [21]
    21. Method of repairing a substrate, or the surface of a substrate, comprising,
    (i) dispersing a quantity of GNP, or a combination of GNP and CNT, into a mixture of monomers of a resin,
    (1) performing between 1 to 10 calendering cycles;
    (2) maintaining the speed of the calendering cycles between 150 and 500 rpm; Y
    (3) reducing the separation between rollers in each calendering cycle between 25 150 and 2 µm;
    (ii) eliminate gases formed under vacuum,
    (iii) add a crosslinking compound, and
     (iv) add the mixture obtained in step (iii) in the substrate or on the surface of the substrate to be repaired and; 30
    (v) cure the mixture obtained in step (iii) by applying a voltage, between 75 and 300V and increasing the temperature in the substrate, or in the surface of the substrate;
    and where the amount of GNP, or the amount of a combination of GNP and CNT, used results, respectively, in concentrations by weight of the mixture obtained in step (iii) above the electrical percolation threshold concentrations of said GNP and CNT
    [22]
    22. The repair method of claim 21 characterized in that in step 5 (i) an amount of GNP or a combination of GNP and CNT is dispersed which results in at least 7% by weight of GNP or, at least 7 % by weight of GNP and at least 0.05% by weight of CNT of the mixture obtained in step (iii).
    [23]
    23. Method for adhering a substrate A to a substrate B characterized in that it comprises:
    (i) dispersing an effective amount of GNP or a combination of GNP and CNT in a mixture of monomers of a resin,
    (1) performing between 1 to 10 calendering cycles;
    (2) maintaining the speed of the calendering cycles between 150 and 500 rpm; and 15
    (3) reducing the separation between rollers in each calendering cycle between 150 and 2 µm;
     (ii) remove occluded gases under vacuum,
    (iii) add a crosslinking compound;
    (iv) add the mixture obtained in (iii) on a surface of the substrate A; twenty
    (v) contacting the surface of the substrate A of step (iv) with a surface of the substrate B;
    (vi) apply a voltage between 75 and 300 V on any of the contact surfaces and increase the temperature to cause the mixture obtained in step (iii) to cure and adhere the contact surfaces 25 of the substrate A and the substrate B respectively;
    and where the amount of GNP, or the amounts of GNP and CNT used, results, respectively, in concentrations by weight of the mixture obtained in step (iii) above the threshold concentrations of electric percolation of said GNP and CNT. 30
    [24]
    24. The method of claim 23 characterized in that in step (i) an amount of GNP or a combination of GNP and CNT is dispersed resulting in the
    minus 7% by weight of GNP or, at least 7% by weight of GNP and at least 0.05% by weight of CNT of the mixture obtained in step (iii).
    [25]
    25. Use of the reinforced resins of claims 9-14 for the manufacture of paints.
    [26]
    26. Use of the reinforced resins of claims 9-14 for manufacturing 5 coatings.
    [27]
    27. Use of the reinforced resins of claims 9-14 for the protection of substrates against adverse weather conditions.
    [28]
    28. The use of claim 27 characterized in that the adverse atmospheric conditions consist of a frost and the protection of the substrates affected by said conditions comprises preventing the formation of ice or releasing the ice formed on said substrates.
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