Bio-based recoverable high-thermal-conductivity dynamic ordered network composite material and preparation method thereof

Abstract

The invention discloses a bio-based recoverable high-thermal-conductivity dynamic ordered network composite material and a preparation method thereof, and is characterized in that the material takes a bio-based multifunctional epoxy system and a carboxylic acid compound containing disulfide bonds as reaction monomers, and the reaction monomers are reacted under the conditions of high temperature and metal salt catalyzed epoxy-carboxylic acid esterification reaction to obtain the bio-based recoverable high-thermal-conductivity dynamic ordered network composite material. A dynamic ordered network structure simultaneously containing disulfide bonds and beta-hydroxyl ester bonds is constructed, and the dynamic ordered network can be used as a springboard for phonon transmission, serves as an efficient'thermal bridge ', and plays a role similar to an ordered'crystal domain', so that higher heat-conducting property is shown when heat-conducting filler is not introduced, high flexibility and intrinsic heat conduction are realized, and the service life of the material is prolonged. And the material is endowed with reprocessing and recycling characteristics. Due to the synergistic existence of carboxyl, hydroxyl generated by epoxy ring opening and metal coordination in the system, and in combination with electrostatic interaction, Van der Waals force and hydrophobic interaction, the material has the adhesion characteristic suitable for a thermal interface at the same time.

Description

Technical Field

[0001] This invention relates to the field of bio-based polymer composite materials and thermal management materials, and in particular to a method for preparing a bio-based recyclable high thermal conductivity dynamic ordered network composite material. This material is particularly suitable for the thermal management of electronic devices that require efficient heat dissipation, good interface compatibility, and environmental friendliness. Background Technology

[0002] As consumer electronics, new energy, and high-power electronic devices develop towards higher integration and higher power density, the heat generated during device operation is constantly increasing. Insufficient heat dissipation efficiency will directly affect the performance stability, lifespan, and safety of these devices. Therefore, developing thermal interface materials with high thermal conductivity and good interface compatibility has become an important research direction in the field of materials science.

[0003] Existing thermal interface materials typically use polymers as the matrix and introduce carbon-based or inorganic thermally conductive fillers to improve their thermal conductivity. However, polymer matrices generally have low intrinsic thermal conductivity, often requiring high filler content to construct effective thermal conduction pathways. This not only increases the processing difficulty but also weakens the material's flexibility and interfacial adhesion, severely hindering efficient phonon transport and ultimately hindering the reduction of interfacial contact thermal resistance. Furthermore, the thermally conductive filler and polymer matrix are usually heterogeneous interfaces; insufficient interfacial compatibility can introduce additional interfacial thermal resistance, limiting the full utilization of the high intrinsic thermal conductivity of the filler.

[0004] In the prior art, various thermal interface material solutions have been proposed. For example, Chinese patent CN202411616930.X discloses a high thermal conductivity phase change thermal interface material, which achieves thermal management by introducing a phase change material and a thermally conductive filler. However, this type of material relies on the phase change process to function, and its instantaneous thermal conductivity and system stability are limited, and it usually requires a high filler content. Chinese patent CN202311786927.8 discloses a graphene thermally conductive film with high in-plane thermal conductivity, but its thermal conductivity exhibits significant anisotropy, and its thermal conductivity in the thickness direction is limited, requiring high interface flatness and pressure application. Chinese patent CN202110495381.5 discloses an expanded graphite thermal interface material. This system mainly relies on physical filling to construct thermal conductive pathways, and the interfacial bonding ability between the filler and the matrix is ​​limited, often requiring a high filler content or large compressive stress to reduce interfacial contact thermal resistance. Dynamic covalent polymer networks, due to their ability to undergo bond exchange reactions under stimuli such as heat and light, resulting in network topology rearrangement, are endowed with remodelable, repairable, and recyclable properties, providing new ideas for the development of sustainable thermal interface materials. However, how to endow dynamic polymer networks with high thermal conductivity through molecular design without relying on high thermal conductivity fillers remains a significant challenge. The intrinsic thermal conductivity of polymers is typically very low (~0.2 W / (m·K)), mainly due to the strong phonon scattering in their amorphous structure.

[0005] In summary, existing thermal interface materials generally suffer from problems such as insufficient intrinsic thermal conductivity of the matrix, high interfacial thermal resistance between the filler and the matrix, and dependence on high filler content or high-pressure conditions when improving thermal conductivity. Furthermore, most systems lack recyclability, making it difficult to simultaneously achieve high thermal conductivity, good interfacial compatibility, and sustainable development requirements. Therefore, there is an urgent need for a novel thermal interface material that can achieve high thermal conductivity with low filler content, effectively reduce the contact thermal resistance of heterogeneous interfaces, and possess good interfacial adhesion and recyclability. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing thermal management materials, such as low intrinsic thermal conductivity of the polymer matrix, high thermal resistance at the heterogeneous interface between the thermally conductive filler and the matrix, and the reliance on high filler content to achieve high thermal conductivity. This invention provides a bio-based, recyclable, high thermal conductivity, dynamically ordered network composite material and its preparation method. This invention abandons the traditional approach of filling the matrix with high thermal conductivity fillers, instead focusing on molecular network structure design. It enhances the intrinsic thermal conductivity of the material by constructing a dynamically ordered covalent network, cleverly integrating recyclability and strong interfacial adhesion.

[0007] In this system, the multifunctional epoxy system reacts with carboxylic acid compounds containing disulfide bonds to form a dynamic and reversible network structure, giving the material excellent flexibility, adhesion, and recyclability. On the other hand, the matrix and thermally conductive filler form a stable interface bond through supramolecular interactions, effectively reducing the contact thermal resistance of the heterogeneous interface. This allows the thermally conductive filler to synergistically construct a continuous and efficient thermally conductive network with the high intrinsic thermal conductivity matrix at a low addition level, thereby significantly improving the overall thermal conductivity of the material, reducing phonon scattering, and achieving rapid heat transfer.

[0008] The objective of this invention is achieved by the following technical solution, wherein the raw material fractions are all parts by mass unless otherwise specified.

[0009] A bio-based, recyclable, highly thermally conductive, dynamically ordered network composite material is developed. The core of this composite lies in a specially designed dynamically ordered network formed by the esterification reaction of bio-based multifunctional epoxy and disulfide-bonded carboxylic acid compounds under metal salt catalysis, via the reaction of epoxy groups and carboxyl groups. This reaction generates two key chemical bonds: (1) β-hydroxy ester bond: generated by the reaction of epoxy ring opening and carboxyl group. The hydroxyl group at the adjacent position can form intramolecular or intermolecular hydrogen bond / coordination bond with ester group or metal ion, promoting the orderly arrangement of local chain segments.

[0010] (2) Dynamic disulfide bond: derived from carboxylic acid compounds containing disulfide bonds, which can undergo reversible exchange reactions under heating conditions.

[0011] The synergistic effect of these two types of bonds ensures that the resulting network is not entirely random. β-hydroxy ester bonds and their associated secondary interactions (such as hydrogen bonds and metal coordination) guide the molecular chains to form locally ordered microregions, similar to "physical cross-linking points" or microcrystalline regions in traditional polymers. These ordered microregions can serve as effective channels or "stepping stones" for phonon transmission, significantly reducing phonon scattering within the network, thus exhibiting a higher intrinsic thermal conductivity than ordinary random network polymers on a macroscopic scale. Dynamic disulfide bonds endow the entire network with the ability to rearrange its topology under thermal stimulation, giving the material thermoplastic processing and recyclability.

[0012] In addition, the abundant polar groups (hydroxyl, carboxyl, ester groups) and possible metal ion coordination centers in the network provide the material with the ability to adhere to a variety of substrates (such as metals, ceramics, and plastics), making it suitable for the interfacial wetting and bonding required for thermal interface materials.

[0013] To further enhance thermal conductivity and meet higher heat dissipation requirements, layered expanded graphite can be introduced into the aforementioned dynamic network matrix. Expanded graphite possesses extremely high in-plane thermal conductivity and good flexibility. In this invention, strong supramolecular interactions such as hydrogen bonds and π-π stacking can be generated between the polar groups in the matrix network and the functional groups or π-electron clouds on the surface of the expanded graphite sheets, thereby achieving excellent interfacial bonding, greatly reducing interfacial thermal resistance, and constructing an efficient and continuous three-dimensional thermal conduction pathway from the graphite sheets to the matrix network.

[0014] The preparation method of the above-mentioned bio-based recyclable high thermal conductivity dynamic ordered network composite material mainly includes the following steps: Preparation of S1 precursor: 100 parts of multifunctional epoxy system were added to a reaction vessel, heated and stirred at 80-150℃ for 5 min, and then 20-50 parts of carboxylic acid compound containing disulfide bond and 1-4 parts of metal salt were added. The reaction was continued to be stirred for 10-90 min to obtain a viscous precursor.

[0015] S3 Thermally conductive filler introduction: When it is necessary to prepare composite materials containing expanded graphite, 10-25 parts of layered expanded graphite are added to the precursor obtained in step S1 and uniformly dispersed by mechanical stirring for 1-2 hours. The entire system gradually transforms into a gel state.

[0016] S3 Molding and Curing: Inject the precursor of step S1 or the mixture of step S2 into a mold and cure it at 120-180℃ and 0.5-5MPa for 0.5-3 h. After cooling, a bio-based recyclable high thermal conductivity dynamic ordered network composite material is obtained.

[0017] The multifunctional epoxy system is epoxidized soybean oil, epoxidized cashew phenol, epoxidized linseed oil, epoxidized palm oil, epoxidized castor oil and their derivatives or combinations thereof. The carboxylic acid compound containing a disulfide bond is at least one of lipoic acid, dithiodipropionic acid, dithiol dihydroxyacetic acid, 2,2'-dithiodibenzoic acid, and 1,2-dithiocyclohexane-3,6-dicarboxylic acid. The expanded graphite has a particle size of 50-300 mesh; The metal salt is at least one of zinc acetate, zinc acetylacetone, zinc chloride, zinc nitrate, zinc stearate, and magnesium acetate.

[0018] The beneficial effects of this invention are as follows: This invention effectively solves the problems of low intrinsic thermal conductivity of polymer matrices, high interfacial thermal resistance between thermally conductive fillers and the reliance on high filler content to achieve high thermal conductivity in existing thermal management materials by constructing a bio-based, recyclable, and dynamically ordered network composite material with high thermal conductivity. By constructing an ordered dynamic network containing β-hydroxy ester bonds and dynamic disulfide bonds, the phonon transport path is optimized at the molecular level, achieving a significantly improved intrinsic thermal conductivity without adding any traditional thermally conductive fillers, fundamentally reducing the dependence on high-content thermally conductive fillers.

[0019] When expanded graphite is introduced, the strong interfacial bonding based on supramolecular effects enables a leap in thermal conductivity even with low filler content, effectively improving the compatibility of heterogeneous interfaces, significantly reducing the contact thermal resistance between the filler and the matrix, while maintaining the flexibility and dynamic properties of the matrix.

[0020] The composite material prepared by this invention possesses high flexibility, hot-press reshaping / recyclability, and excellent adhesion to heat dissipation interfaces, effectively filling microscopic voids at the interface. Its overall performance far surpasses that of traditional filled or ordinary dynamic polymer thermal interface materials. The preparation process of this invention is simple and mild, facilitating large-scale production. It exhibits comprehensive advantages in thermal conductivity, interface compatibility, and sustainability, making it suitable for thermal management fields such as consumer electronics, new energy, and medical heat dissipation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the cross-linking reaction of molecules in this dynamic ordered network.

[0022] Figure 2 This is a schematic diagram of the adhesion mechanism of the dynamic ordered network.

[0023] Figure 3 This is a scanning electron microscope (SEM) image of the thermally conductive network of the dynamic ordered network composite material. Detailed Implementation

[0024] The present invention will be further described below through specific embodiments. It should be noted that the embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make non-essential improvements and adjustments to the present invention based on the above content. Example

[0025] 100 parts of epoxidized soybean oil were added to a reaction vessel, heated and stirred at 150°C for 5 min, followed by the addition of 20 parts of thioctic acid and 1 part of zinc acetate, and the reaction was continued with stirring for 10 min to obtain a viscous precursor. The precursor was injected into a mold and cured at 150°C and 0.5 MPa for 2 h. After cooling, a bio-based recyclable, highly thermally conductive, dynamically ordered network material was obtained. Example

[0026] 100 parts of epoxy castor oil were added to a reaction vessel, heated and stirred at 150°C for 10 min, followed by the addition of 30 parts of dithiodipropionic acid and 1 part of zinc nitrate. The reaction was continued with stirring for 1 h to obtain a viscous precursor. The precursor was injected into a mold and cured at 150°C and 0.5 MPa for 30 min. After cooling, a bio-based recyclable, highly thermally conductive, dynamically ordered network material was obtained. Example

[0027] 100 parts of epoxidized linseed oil were added to a reaction vessel, heated and stirred at 150°C for 5 min, followed by the addition of 50 parts of 2,2'-dithiodibenzoic acid and 2 parts of zinc acetylacetonate, and the reaction was continued with stirring for 2 h to obtain a viscous precursor. The precursor was injected into a mold and cured at 150°C and 1 MPa for 45 min. After cooling, a bio-based recyclable, highly thermally conductive, dynamically ordered network material was obtained. Example

[0028] 100 parts of epoxidized soybean oil were added to a reaction vessel, heated and stirred at 150°C for 5 min, followed by the addition of 20 parts of thioctic acid and 1 part of zinc acetate, and the reaction was continued for 10 min to obtain a viscous precursor. 10 parts of expanded graphite were added to the precursor and mechanically stirred for 2 h to disperse it uniformly, gradually transforming the entire system into a gel state. The precursor was injected into a mold and cured at 150°C and 0.5 MPa for 30 min. After cooling, a bio-based recyclable, highly thermally conductive, dynamically ordered network composite material was obtained. Example

[0029] 100 parts of epoxidized soybean oil were added to a reaction vessel, heated and stirred at 150°C for 5 min, followed by the addition of 20 parts of thioctic acid and 1 part of zinc acetate, and the reaction was continued for 10 min to obtain a viscous precursor. 20 parts of expanded graphite were added to the precursor and mechanically stirred for 2 h to disperse it uniformly, gradually transforming the entire system into a gel state. The precursor was injected into a mold and cured at 150°C and 0.5 MPa for 30 min. After cooling, a bio-based recyclable, highly thermally conductive, dynamically ordered network composite material was obtained. Example

[0030] 100 parts of epoxidized soybean oil were added to a reaction vessel, heated and stirred at 150°C for 5 min, followed by the addition of 20 parts of thioctic acid and 1 part of zinc acetate, and the reaction was continued for 10 min to obtain a viscous precursor. 25 parts of expanded graphite were added to the precursor and mechanically stirred for 2 h to disperse it uniformly, gradually transforming the entire system into a gel state. The precursor was injected into a mold and cured at 150°C and 0.5 MPa for 30 min. After cooling, a bio-based, recyclable, highly thermally conductive, dynamically ordered network composite material was obtained. Example

[0031] 100 parts of epoxidized soybean oil were added to a reaction vessel, heated at 150°C and stirred for 5 min. Then, 50 parts of thioctic acid and 3 parts of zinc acetate were added, and the reaction was continued for 30 min to obtain a viscous precursor. 10 parts of expanded graphite were added to the precursor and mechanically stirred for 2 h to disperse it evenly, gradually transforming the entire system into a gel state. The precursor was injected into a mold and cured at 150°C and 2 MPa for 1 h. After cooling, a bio-based, recyclable, highly thermally conductive, dynamically ordered network composite material was obtained.

[0032] Comparative Example 1 Bisphenol A type epoxy resin (E-51) and methyltetrahydrophthalic anhydride were mixed at a molar ratio of epoxy group to anhydride group of 1:0.85. One part of accelerator (DMP-30) was added, and the mixture was poured into a mold and cured at 120℃ / 2 h + 150℃ / 4 h to obtain a hard and brittle epoxy network resin.

[0033] The test results are shown in Table 1: Table 1. Performance Comparison of Dynamically Ordered Network Composite Material and Ordinary Epoxy Network parameter Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Thermal conductivity (W / mK) 2.21 2.24 2.29 3.12 4.34 5.40 3.72 0.24 Adhesion strength (kPa) 323 388 402 271 252 244 326 36 Thermal conductivity (W / mK) after three repeated processing steps 2.06 2.11 2.14 2.89 3.94 5.22 3.57 Cannot be processed repeatedly Tensile strength recovery rate after three repeated processing 92% 94% 95% 89% 88% 85% 92% Cannot be processed repeatedly Recovery rate of elongation at break after three repeated processing 87% 87% 89% 85% 88% 84% 87% Cannot be processed repeatedly In summary, by comparing Examples 1-3 and Comparative Example 1, Comparative Example 1 exhibits lower thermal conductivity and adhesion strength, making it unsuitable for repeated processing and recycling. This indicates that the thermal conductivity of ordinary epoxy networks is poor, confirming the effectiveness of dynamic ordered network design in improving intrinsic thermal conductivity and interfacial adhesion performance, and achieving reprocessability and recycling. In Examples 4-6 of this invention, the thermal conductivity gradually increases after adding different amounts of expanded graphite. By constructing a bio-based dynamic ordered network and introducing a small amount of expanded graphite thermally conductive filler, the composite material significantly improves the intrinsic thermal conductivity and overall thermal conductivity of the matrix while maintaining good flexibility and interfacial adhesion performance. This approach balances high thermal conductivity with recyclability, demonstrating broad application prospects in the field of high-performance, sustainable thermal interface materials.

[0034] The above embodiments have described the specific content of the present invention in detail, but the present invention is not limited to the embodiments described. Those skilled in the art can make equivalent substitutions, all of which should be covered within the protection scope of the present invention.

Claims

1. A bio-based, recyclable, highly thermally conductive, dynamically ordered network composite material, characterized in that, The composite material is based on a dynamic and ordered cross-linked network formed by esterification of a bio-based multifunctional epoxy system and a carboxylic acid compound containing disulfide bonds under the catalysis of a metal salt; the dynamic and ordered cross-linked network contains both dynamically exchangeable disulfide bonds and β-hydroxy ester bonds; the intrinsic thermal conductivity of the composite material is not less than 1.6 W / (m·K) when no external thermally conductive filler is added.

2. The bio-based recyclable high thermal conductivity dynamically ordered network composite material according to claim 1, characterized in that, The main raw materials of this composite material are composed of the following components, in parts by mass: 100 parts of multifunctional epoxy system 20-50 parts of carboxylic acid compounds containing disulfide bonds 10-25 parts expanded graphite 1-4 parts of metal salt The multifunctional epoxy system is epoxidized soybean oil, epoxidized cashew phenol, epoxidized linseed oil, epoxidized palm oil, epoxidized castor oil and their derivatives or combinations thereof. The carboxylic acid compound containing a disulfide bond is at least one of lipoic acid, dithiodipropionic acid, dithiol dihydroxyacetic acid, 2,2'-dithiodibenzoic acid, and 1,2-dithiocyclohexane-3,6-dicarboxylic acid. The expanded graphite has a particle size of 50-300 mesh; The metal salt is at least one of zinc acetate, zinc acetylacetone, zinc chloride, zinc nitrate, zinc stearate, and magnesium acetate.

3. A method for preparing the bio-based recyclable high thermal conductivity dynamic ordered network composite material as described in claim 1 or 2, characterized in that, Includes the following steps: Preparation of S1 precursor: 100 parts of multifunctional epoxy system were added to a reaction vessel, heated and stirred at 80-150℃ for 5 min, then 20-50 parts of carboxylic acid compound containing disulfide bond and 1-4 parts of metal salt were added, and the reaction was continued to be stirred for 10-90 min to obtain a viscous precursor. S3 Thermally conductive filler introduction: When it is necessary to prepare composite materials containing expanded graphite, 10-25 parts of layered expanded graphite are added to the precursor obtained in step S1 and uniformly dispersed by mechanical stirring for 1-2 hours. The whole system gradually transforms into a gel state. S3 Molding and Curing: Inject the precursor of step S1 or the mixture of step S2 into a mold and cure it at 120-180℃ and 0.5-5 MPa for 0.5-3 h. After cooling, a bio-based recyclable high thermal conductivity dynamic ordered network composite material is obtained.

4. Application of a bio-based recyclable high thermal conductivity dynamic ordered network composite material in the wetting and bonding of thermal interface materials.

Images