Recyclable high-thermal-conductivity polyethylene glycol flexible phase change composite material and preparation method thereof

Abstract

The invention discloses a recyclable high-thermal-conductivity polyethylene glycol flexible phase change composite material and a preparation method thereof, and is characterized in that based on a molecule and filler network design, firstly, an anhydride group is introduced into an ethylene propylene diene monomer (EPDM) molecular chain through chemical grafting, and an anhydride site with high reaction activity is constructed; a dynamic covalent cross-linked network is constructed based on a zinc acetate catalyzed cross-linking reaction of a flexible epoxy compound and anhydridized ethylene propylene diene monomer at a high temperature, on one hand, zinc acetate serves as a reactant to participate in an anhydride group to form a coordinate bond with zinc ions, and on the other hand, zinc acetate serves as a catalyst to activate an epoxy group and accelerate the reaction of epoxy and the anhydride group; generating a dynamic ester bond; the preparation method comprises the following steps: by taking a composite material as a flexible matrix, mechanically blending a polyethylene glycol (PEG) phase change component, a carboxyl carbon nanotube and a hybrid heat-conducting filler composed of spherical aluminum oxide through mixing, and carrying out high-temperature hot press molding to prepare the polyethylene glycol flexible phase change composite material which has high enthalpy of phase change, high heat conductivity and stable shape and can be repeatedly processed.

Description

Technical Field

[0001] The invention relates to the field of polymer material preparation, and in particular to a recyclable high-thermal-conductivity polyethylene glycol flexible phase-change composite material and a preparation method thereof. Background Art

[0002] Phase change materials refer to materials that undergo phase changes within a certain temperature range and can absorb or release a large amount of thermal energy. They have the advantages of high energy storage density and stable chemical properties, and are widely used in the field of thermal management. Among them, organic phase change materials have the characteristics of high heat storage density, non-toxicity and low cost, and have been widely used in modern electronics, high-power batteries, building energy conservation and energy storage conversion systems. However, organic solid-liquid PCM has three key bottlenecks: low inherent thermal conductivity (generally between 0.15-0.5 W / mK), melt leakage during phase change, and solid rigidity, which seriously restrict its application in the field of energy storage and thermal management. Although the performance of phase change materials can be improved by physical blending of thermal conductive fillers, 3D thermal conductive network impregnation and other methods, the preparation method is complicated, or it is difficult to solve the above defects at the same time. By introducing phase change materials into flexible matrices, it is expected that the flexibility, thermal conductivity and mechanical properties of phase change composite materials can be improved, and they can be repeatedly processed. However, it is currently difficult to simultaneously improve the thermal conductivity and mechanical properties of phase change materials while maintaining flexibility and reprocessability. That is, the flexibility, high thermal conductivity and high mechanical properties of phase change materials cannot be taken into account at the same time. Therefore, it is of great significance to develop flexible phase change composite materials with high thermal conductivity and high phase change enthalpy that can be repeatedly processed.

[0003] Rubber materials have good flexibility, high elasticity and chemical stability, and can be used as elastic matrix of thermal interface materials for encapsulating phase change materials. However, rubber has low intrinsic thermal conductivity and mainly relies on phonon heat conduction. Due to the amorphous structure and vibration of its macromolecular chain, it will cause a large amount of phonon scattering, so its thermal conductivity is extremely poor, which limits its application in the field of thermal management. Therefore, its thermal conductivity must be improved. Nanomaterials represented by graphene, carbon nanotubes, boron nitride, aluminum oxide, etc. have excellent intrinsic thermal conductivity and can be used as thermal conductive fillers to fill the rubber matrix, forming a continuous thermal conductive channel inside the rubber, significantly improving the thermal conductivity of the rubber.

[0004] Chinese patent CN117801790A discloses a rapid synthesis method of nano phase change microcapsules encapsulated by silicon dioxide, wherein the synthesis method is to prepare phase change microcapsules by wrapping paraffin with styrene-butadiene-styrene copolymer as the capsule wall. Although the microcapsules have a high encapsulation rate, the preparation process is complicated, the production cost is high, and the thermal conductivity and mechanical strength are also low; Chinese patent CN119119966A discloses a composite phase change material and a preparation method thereof, wherein a solid-liquid phase change material is filled into the pores of a porous material, and then a carbohydrate is dehydrated and condensed on the outer surface of the porous material to form a carbon shell to close and / or semi-close a part of the pores of the porous material. Although the preparation process is simple, the solid rigidity of the phase change material is not solved. Zhao Mengyang et al., Fine Chemicals, 2022, 39(6): 1155-1161, used polyethylene glycol and aminopropyl-terminated polydimethylsiloxane as soft segments, toluene-2,4-diisocyanate as hard segments, and carbon nanotubes as thermal conductive materials to prepare thermally conductive enhanced polyurethane-based flexible shaped phase change materials by a one-pot method, but its thermal conductivity and phase change enthalpy were low; Wang Chenyang et al., Advanced Materials, 2024, 36, 2309723, proposed a multiple hydrogen bonding strategy to synthesize supramolecular polyurethane with high latent heat storage performance and high mechanical strength using polyethylene glycol (PEG) as the phase change energy storage functional segment, which has high phase change enthalpy, high mechanical strength and heavy processing characteristics, but no thermal conductivity is involved. Therefore, the development of flexible phase change composite materials with excellent comprehensive performance is still challenging. Summary of the invention

[0005] The purpose of the present invention is to provide a recyclable high thermal conductivity polyethylene glycol flexible phase change composite material and a preparation method thereof in view of the deficiencies in the prior art. The present invention is characterized in that based on the molecular and filler network design, anhydride groups are introduced into ethylene propylene diene monomer (EPDM) molecular chains by chemical grafting, anhydride reaction sites are introduced, the reaction activity of anhydride and epoxy groups is utilized, and a dynamic covalent network is constructed based on zinc acetate catalyzing the reaction of flexible epoxy compounds and anhydride ethylene propylene diene monomer rubber. Zinc acetate forms coordination bonds with anhydride groups and on the other hand, acts as a catalyst to activate epoxy groups, accelerate the reaction of epoxy and anhydride groups, and generate dynamic ester bonds; further, a hybrid thermal conductive filler composed of polyethylene glycol (PEG) phase change components, carboxylated carbon nanotubes and spherical alumina is mechanically blended and hot-pressed at high temperature to prepare a polyethylene glycol flexible phase change composite material with high phase change enthalpy, high thermal conductivity, stable shape and repeatable processing. One-dimensional carboxyl carbon nanotubes are coated with zero-dimensional spherical alumina, and the hybrid thermal conductive filler imparts high thermal conductivity. At the same time, the thermal conductive filler network and the dynamic covalent cross-linking network effectively encapsulate PEG, giving it repeatable processing and recycling characteristics. The phase change composite material prepared by the present invention has high thermal conductivity, high phase change enthalpy, recyclability and mechanical flexibility, and can be used in the field of thermal management to effectively dissipate heat from electronic devices.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The raw material fractions mentioned herein are by mass unless otherwise specified.

[0007] A recyclable high thermal conductivity polyethylene glycol flexible phase change composite material, the main raw materials of which are composed of the following components, calculated by weight: 100 parts of EPDM rubber 1-5 parts of anhydride compound 3-6 parts of zinc acetate Epoxy compound 20-25 parts Polyethylene glycol 150-200 parts Thermally conductive filler 1-20 parts Wherein, the acid anhydride compound is any one of itaconic anhydride, succinic anhydride and succinic anhydride; The epoxy compound is any one of epoxy soybean oil, epoxy linseed oil and epoxy tetrahydrophthalate; The molecular weight of the polyethylene glycol is 6000 g / mol; The thermally conductive filler is a hybrid thermally conductive filler composed of carboxylated carbon nanotubes and spherical alumina, and the mass ratio of the carboxylated carbon nanotubes to the spherical alumina is 1:2.

[0008] A method for preparing a recyclable high thermal conductivity polyethylene glycol flexible phase change composite material comprises the following steps: S1: Preparation of dynamically cross-linked anhydride EPDM rubber 100 parts of ethylene propylene diene monomer rubber (EPDM) are added into a torque rheometer at 180°C and 50 r / min, and kneaded for 1 min. Then, 1-5 parts of anhydride compound and 0.1-1 part of di-tert-butyl peroxide diisopropylbenzene are added into the internal mixer and mixed evenly, and the mixture is reacted continuously for 5-10 min. 3-6 parts of zinc acetate and 20-25 parts of epoxy compound are added into the torque rheometer, the rotation speed is controlled at 10-60 r / min, and the mixture is reacted continuously for 7-15 min, so that the anhydride group, zinc ion and epoxy group are fully reacted, and the dynamically cross-linked anhydride ethylene propylene diene monomer rubber is prepared.

[0009] S2: Preparation of polyethylene glycol flexible phase change composites The above-prepared dynamically cross-linked anhydride EPDM rubber is used as a flexible matrix, added to a double-roll open mill, mixed at room temperature, and 1-20 parts of carboxylated carbon nanotubes and spherical alumina hybrid thermal conductive fillers are added to make the thermal conductive fillers evenly dispersed in the rubber matrix to form a strong interaction and reduce the interfacial thermal resistance between the thermal conductive fillers and the flexible matrix. Subsequently, 150-200 parts of polyethylene glycol phase change components are added and mixed on a double-roll mill to evenly and completely disperse in the flexible matrix to form a good package. Finally, hot pressing is performed at 50-120°C and 3-10 MPa for 1-5 min to obtain a polyethylene glycol flexible phase change composite material.

[0010] The present invention has the following advantages: Based on the design of molecular and filler network, the dynamic cross-linking network of flexible matrix and the interface between thermal conductive filler and matrix are constructed, in order to reduce the interfacial thermal resistance and improve the thermal conductivity, while the phase change component is infiltrated into the matrix network to maintain flexibility. Firstly, the anhydride group is introduced into the molecular chain of ethylene propylene diene monomer (EPDM) by chemical grafting under the action of initiator, and the anhydride site with high reactivity is successfully constructed; breaking through the traditional blending method of physically blending flexible epoxy compounds as plasticizers, zinc acetate is used to catalyze the esterification reaction of epoxy compounds and anhydrides, so that the anhydride group forms a coordination bond with zinc ions, and on the other hand, it acts as a catalyst to activate the epoxy group, accelerate the reaction of epoxy and anhydride groups, and generate dynamic ester bonds; one-dimensional carboxyl carbon nanotubes are coated with zero-dimensional spherical alumina to form a hybrid thermal conductive filler to synergistically enhance thermal conductivity, and the polyethylene glycol (PEG) phase change component, thermal conductive filler and rubber matrix are mixed evenly, and hot-pressed at high temperature to prepare polyethylene glycol flexible phase change composite materials with high phase change enthalpy, high thermal conductivity, stable shape and repeatable processing.

[0011] The thermally conductive filler network and the dynamic covalent cross-linking network effectively encapsulate PEG. The dynamic covalent network imparts repeatable processing and recycling characteristics. The entire system reduces the interfacial thermal resistance between the thermally conductive filler and the flexible matrix, allowing the phase change composite material to maintain flexibility and high phase change enthalpy at a high PEG content, and can be used for phase change thermal management of electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Molecular structure of polyethylene glycol flexible phase change composite material.

[0013] Figure 2 This is a photo of the mechanical flexibility of polyethylene glycol flexible phase change composite materials.

[0014] Figure 3 Demonstration of thermal management application scenarios of polyethylene glycol flexible phase change composite materials. DETAILED DESCRIPTION

[0015] The present invention is further described below through specific examples. It should be noted that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make non-essential improvements and adjustments to the present invention based on the contents of the present invention described above. Example 1

[0016] 100 parts of ethylene propylene diene monomer (EPDM) were added into a torque rheometer at 180℃ and 50 r / min and mixed for 1 min. Then, 1 part of itaconic anhydride and 0.2 parts of di-tert-butyl peroxide diisopropylbenzene were added into the internal mixer and mixed evenly. The mixture was reacted continuously for 5 min. 3 parts of zinc acetate and 20 parts of epoxidized soybean oil were then added into the torque rheometer. The speed was controlled at 30 r / min and the mixture was reacted continuously for 7 min. The anhydride groups, zinc ions and epoxy groups were fully reacted to prepare the dynamically cross-linked anhydride EPDM.

[0017] The above-prepared dynamically cross-linked anhydride EPDM rubber was used as a flexible matrix and added to a double-roll mill for mixing at room temperature. 5 parts of carboxylated carbon nanotubes and spherical alumina hybrid thermal conductive fillers were added to make the thermal conductive fillers evenly dispersed in the rubber matrix to form a strong interaction. Then 150 parts of polyethylene glycol 6000 were added and mixed on a double-roll mill to evenly and completely disperse in the flexible matrix to form a good package. Finally, hot pressing was performed at 50°C and 5 MPa for 2 min to obtain a polyethylene glycol flexible phase change composite material. According to the test, the thermal conductivity of the phase change composite material was 0.67 W / mK, the melting enthalpy was 132 J / g, the tensile strength was 1.52 MPa, the mechanical strength recovery rate was 87% after repeated processing for 3 times, and there was no leakage after heating at 80°C for 5 h. Example 2

[0018] 100 parts of ethylene propylene diene monomer (EPDM) were added into a torque rheometer at 180℃ and 50 r / min and mixed for 1 min. Then, 3 parts of itaconic anhydride and 0.5 parts of di-tert-butyl peroxide diisopropylbenzene were added into the internal mixer and mixed evenly. The mixture was reacted continuously for 5 min. 3 parts of zinc acetate and 20 parts of epoxidized soybean oil were then added into the torque rheometer. The speed was controlled at 30 r / min and the mixture was reacted continuously for 7 min. The anhydride groups, zinc ions and epoxy groups were fully reacted to prepare the dynamically cross-linked anhydride EPDM.

[0019] The above-prepared dynamically cross-linked anhydride EPDM rubber was used as a flexible matrix and added to a double-roll mill for mixing at room temperature. 5 parts of carboxylated carbon nanotubes and spherical alumina hybrid thermal conductive fillers were added to make the thermal conductive fillers uniformly dispersed in the rubber matrix to form a strong interaction. Then 150 parts of polyethylene glycol 6000 were added and mixed on a double-roll mill to uniformly and completely dispersed in the flexible matrix to form a good package. Finally, hot pressing was performed at 50°C and 5 MPa for 2 min to obtain a polyethylene glycol flexible phase change composite material. According to the test, the thermal conductivity of the phase change composite material was 0.79 W / mK, the melting enthalpy was 138 J / g, the tensile strength was 2.23 MPa, the mechanical strength recovery rate was 90% after repeated processing for 3 times, and there was no leakage after heating at 80°C for 5 h. Example 3

[0020] 100 parts of ethylene propylene diene monomer (EPDM) were added into a torque rheometer at 180℃ and 50 r / min and mixed for 1 min. Then, 3 parts of succinic anhydride and 0.3 parts of di-tert-butyl peroxide diisopropylbenzene were added into the internal mixer and mixed evenly. The mixture was reacted continuously for 7 min. 4 parts of zinc acetate and 22 parts of epoxy linseed oil were added into the torque rheometer. The speed was controlled at 50 r / min and the mixture was reacted continuously for 10 min. The anhydride groups, zinc ions and epoxy groups were fully reacted to prepare the dynamically cross-linked anhydride ethylene propylene diene monomer (EPDM).

[0021] The above-prepared dynamically cross-linked anhydride EPDM rubber was used as a flexible matrix and added to a double-roll mill for mixing at room temperature. 8 parts of carboxylated carbon nanotubes and spherical alumina hybrid thermal conductive fillers were added to make the thermal conductive fillers evenly dispersed in the rubber matrix to form a strong interaction. Then 160 parts of polyethylene glycol 6000 were added and mixed evenly and completely dispersed in the flexible matrix on a double-roll mill to form a good package. Finally, hot pressing was performed at 80℃ and 3 MPa for 2 min to obtain a polyethylene glycol flexible phase change composite material. According to the test, the thermal conductivity of the phase change composite material was 1.03 W / mK, the melting enthalpy was 144 J / g, the tensile strength was 1.82 MPa, the mechanical strength recovery rate was 83% after repeated processing for 3 times, and there was no leakage after heating at 80℃ for 5 h. Example 4

[0022] 100 parts of ethylene propylene diene monomer (EPDM) were added into a torque rheometer at 180℃ and 50 r / min and mixed for 1 min. Then, 4 parts of succinic anhydride and 0.4 parts of di-tert-butyl peroxide diisopropylbenzene were added into the internal mixer and mixed evenly. The mixture was reacted continuously for 8 min. 5 parts of zinc acetate and 23 parts of epoxy tetrahydrophthalate were added into the torque rheometer. The speed was controlled at 50 r / min and the mixture was reacted continuously for 10 min. The anhydride groups, zinc ions and epoxy groups were fully reacted to prepare the dynamically cross-linked anhydride ethylene propylene diene monomer (EPDM).

[0023] The above-prepared dynamically cross-linked anhydride EPDM rubber was used as a flexible matrix and added to a double-roll mill for mixing at room temperature. 12 parts of carboxylated carbon nanotubes and spherical alumina hybrid thermal conductive fillers were added to make the thermal conductive fillers uniformly dispersed in the rubber matrix to form a strong interaction. Then 180 parts of polyethylene glycol 6000 were added and mixed on a double-roll mill to uniformly and completely dispersed in the flexible matrix to form a good package. Finally, hot pressing was performed at 90℃ and 6 MPa for 3 min to obtain a polyethylene glycol flexible phase change composite material. According to the test, the thermal conductivity of the phase change composite material was 1.22 W / mK, the melting enthalpy was 148 J / g, the tensile strength was 2.06 MPa, the mechanical strength recovery rate was 81% after repeated processing for 3 times, and there was no leakage after heating at 80℃ for 5 h. Example 5

[0024] 100 parts of ethylene propylene diene monomer (EPDM) were added into a torque rheometer at 180℃ and 50 r / min and mixed for 1 min. Then, 5 parts of succinic anhydride and 0.8 parts of di-tert-butyl peroxide diisopropylbenzene were added into the internal mixer and mixed evenly. The mixture was reacted for 10 min. Then, 6 parts of zinc acetate and 25 parts of epoxidized soybean oil were added into the torque rheometer. The speed was controlled at 60 r / min and the mixture was reacted for 12 min. The anhydride groups, zinc ions and epoxy groups were fully reacted to prepare the dynamically cross-linked anhydride EPDM.

[0025] The above-prepared dynamically cross-linked anhydride EPDM rubber was used as a flexible matrix and added to a double-roll mill for mixing at room temperature. 20 parts of carboxylated carbon nanotubes and spherical alumina hybrid thermal conductive fillers were added to make the thermal conductive fillers uniformly dispersed in the rubber matrix to form a strong interaction. Subsequently, 200 parts of polyethylene glycol 6000 were added and mixed on a double-roll mill to uniformly and completely dispersed in the flexible matrix to form a good package. Finally, hot pressing was performed at 100°C and 8 MPa for 5 min to obtain a polyethylene glycol flexible phase change composite material. According to the test, the thermal conductivity of the phase change composite material was 1.32 W / mK, the melting enthalpy was 156 J / g, the tensile strength was 2.37 MPa, the mechanical strength recovery rate was 81% after repeated processing for 3 times, and there was no leakage after heating at 80°C for 5 h.

[0026] In summary, the embodiments of the present invention, in a dynamically cross-linked anhydride EPDM rubber flexible matrix, co-encapsulates the polyethylene glycol phase change material through a hybrid thermally conductive filler to construct a thermally conductive network, endowing the phase change composite material with high thermal conductivity and mechanical properties, and can perform functions such as repeated processing, and can be applied to the field of phase change thermal management.

[0027] The above embodiments describe the specific contents of the present invention in detail, but the present invention is not limited to the embodiments, and those skilled in the art can make equivalent substitutions, which should be included in the protection scope of the present invention.

Claims

1. A recyclable high thermal conductivity polyethylene glycol flexible phase change composite material, characterized in that The main raw materials of the phase change composite material are composed of the following components, calculated by weight: EPDM 100 parts 1-5 parts of anhydride compound 3-6 parts of zinc acetate Epoxy compound 20-25 parts Polyethylene glycol 150-200 parts Thermally conductive filler 1-20 parts Wherein, the acid anhydride compound is any one of itaconic anhydride, succinic anhydride and succinic anhydride; The epoxy compound is any one of epoxy soybean oil, epoxy linseed oil and epoxy tetrahydrophthalate; The molecular weight of the polyethylene glycol is 6000 g / mol; The thermally conductive filler is a hybrid thermally conductive filler composed of carboxylated carbon nanotubes and spherical alumina, and the mass ratio of the carboxylated carbon nanotubes to the spherical alumina is 1:

2.

2. A method for preparing a recyclable high thermal conductivity polyethylene glycol flexible phase change composite material, characterized in that: The steps include: S1: Preparation of dynamically cross-linked anhydride EPDM rubber 100 parts of EPDM are added to a torque rheometer at 180°C and 50 r / min, and kneaded for 1 min. Then, 1-5 parts of anhydride compound and 0.1-1 part of di-tert-butyl peroxide diisopropylbenzene are added to the internal mixer and mixed evenly, and the reaction is continued for 5-10 min. 3-6 parts of zinc acetate and 20-25 parts of epoxy compound are added to the torque rheometer, the speed is controlled to 10-60 r / min, and the reaction is continued for 7-15 min, so that the anhydride group, zinc ion and epoxy group are fully reacted, and the dynamically cross-linked anhydride EPDM rubber is prepared. S2: Preparation of polyethylene glycol flexible phase change composites The above-prepared dynamically cross-linked anhydride EPDM rubber is used as a flexible matrix, added to a double-roll open mill, mixed at room temperature, and 1-20 parts of carboxylated carbon nanotubes and spherical alumina hybrid thermal conductive fillers are added to make the thermal conductive fillers evenly dispersed in the rubber matrix to form a strong interaction and reduce the interfacial thermal resistance between the thermal conductive fillers and the flexible matrix. Subsequently, 150-200 parts of polyethylene glycol phase change components are added and mixed on a double-roll mill to evenly and completely disperse in the flexible matrix to form a good package. Finally, hot pressing is performed at 50-120°C and 3-10 MPa for 1-5 min to obtain a polyethylene glycol flexible phase change composite material.

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