Heat-conducting protective polyurethane elastomer

Abstract

The invention provides a heat-conducting protective polyurethane elastomer, and belongs to the technical field of polymer composite materials. The heat-conducting protective polyurethane elastomer comprises a polyurethane matrix and a composite heat-conducting filler dispersed in the polyurethane matrix, the composite heat-conducting filler is a compound system of flaky boron nitride modified by a polydopamine-silane coupling agent hybrid layer and spherical zinc oxide modified by tannic acid. According to the invention, flaky boron nitride modified by a polydopamine-silane coupling agent hybrid layer and spherical zinc oxide modified by tannic acid form a compound heat-conducting filler system, and the flaky boron nitride and the spherical zinc oxide form an efficient and synergistic heat-conducting network in a polyurethane matrix. The sheet-shaped BN is easy to be in horizontal orientation lap joint in a matrix to form a plane heat conduction main path with low thermal resistance, and the spherical ZnO effectively fills tiny gaps which cannot be touched by the BN sheet layers and bridges adjacent BN sheets, so that a two-dimensional plane network is upgraded into a three-dimensional interwoven network. According to the structure, a high-efficiency heat conduction channel can be formed under the condition of lower filling amount.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a thermally conductive and protective polyurethane elastomer. Background Technology

[0002] As electronic devices evolve towards higher power, higher integration, and miniaturization, efficient heat dissipation has become a key technological challenge. Polyurethane (PU) elastomers are often used as sealing, potting, or protective materials for electronic components due to their excellent wear resistance, oil resistance, cushioning, and designability. However, pure polyurethane has an extremely low thermal conductivity, which cannot meet heat dissipation requirements.

[0003] Existing technologies typically improve thermal conductivity by adding high thermal conductivity fillers (such as aluminum nitride, boron nitride, alumina, and silicon carbide) to the polyurethane matrix. However, this method faces two common challenges: 1. High filler content and performance contradiction: To achieve a high thermal conductivity (e.g., >1.0 W / m·K), a large amount of filler (volume fraction >30%) is often required. This leads to a sharp increase in the viscosity of the composite material, making processing difficult, and severely impairing the inherent high elasticity, flexibility, and mechanical strength of polyurethane, causing the material to become hard and brittle.

[0004] 2. Interfacial thermal resistance problem: The inorganic thermally conductive filler has poor compatibility with the organic polyurethane matrix, weak interfacial bonding, and high interfacial thermal resistance, which seriously restricts the effective formation of thermal conduction pathways (thermal conduction networks) and prevents the filler from fully exerting its thermal conductivity advantages.

[0005] Therefore, developing a composite material that can achieve efficient thermal conductivity while maintaining the excellent elasticity and mechanical properties of polyurethane with a reduced amount of thermally conductive filler is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention aims to provide a thermally conductive and protective polyurethane elastomer.

[0007] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of the present invention is a thermally conductive and protective polyurethane elastomer, comprising a polyurethane matrix and a composite thermally conductive filler dispersed in the polyurethane matrix; The composite thermally conductive filler is a compound system of lamellar boron nitride modified with a polydopamine-silane coupling agent hybrid layer and spherical zinc oxide modified with tannic acid.

[0008] In a preferred embodiment of the present invention, the composite thermally conductive filler accounts for 10% to 20% of the mass of the polyurethane elastomer.

[0009] In a preferred embodiment of the present invention, the mass ratio of the sheet-like boron nitride modified with the polydopamine-silane coupling agent hybrid layer to the spherical zinc oxide modified with tannic acid is 3:(1~3).

[0010] In a preferred embodiment of the present invention, the method for preparing the sheet-like boron nitride modified with a polydopamine-silane coupling agent hybrid layer includes the following steps: S1. Disperse the boron nitride flakes in Tris-HCl buffer, then add dopamine hydrochloride to react 1, to obtain polydopamine-modified boron nitride; S2. The polydopamine-modified boron nitride is dispersed in an aqueous ethanol solution, and then a silane coupling agent is added to carry out reaction 2 to obtain the sheet-like boron nitride modified with a polydopamine-silane coupling agent hybrid layer.

[0011] More preferably, the pH of the Tris-HCl buffer solution is 8.5; the mass ratio of the boron nitride flakes to dopamine hydrochloride is 1:(0.1-0.3); the reaction 1 is carried out at room temperature for 12-24 hours under stirring conditions; the average particle size of the boron nitride flakes is 15 μm and the thickness is 0.5-1 μm.

[0012] More preferably, the silane coupling agent is KH-550; the mass ratio of the plate-like boron nitride to the silane coupling agent is 1:(0.15~0.3); the reaction 2 is a reflux reaction at 60~80℃ for 4~6 hours; and the concentration of ethanol in the ethanol aqueous solution is 90% (v / v).

[0013] In a preferred embodiment of the present invention, the method for preparing the tannic acid-modified spherical zinc oxide is as follows: ZnO is dispersed in water, the pH is adjusted, and then tannic acid is added to carry out reaction 3 to obtain the tannic acid-modified spherical zinc oxide.

[0014] More preferably, the average particle size of the ZnO is 0.5 μm; the mass ratio of ZnO to tannic acid is 5:(0.5~1.5); the pH is 3~3.5; and the reaction 3 is carried out by stirring at 50~60℃ for 2~4 hours.

[0015] In the design of thermally conductive and protective polyurethane elastomers, polydopamine-modified lamellar boron nitride (PBN) is chosen primarily due to its strong adhesion and abundant active functional groups. The PDA layer not only significantly enhances the interfacial bonding between BN and the polyurethane matrix and reduces interfacial thermal resistance through hydrogen bonding and chemical interactions, but also serves as a stabilizing platform providing sites for subsequent silane coupling agent grafting. The two work synergistically to form a hybrid modification layer, thereby effectively improving the dispersibility of BN and constructing an efficient planar thermally conductive pathway. Meanwhile, tannic acid is used to modify spherical zinc oxide, utilizing the interaction between tannic acid and Zn... 2+The strong coordination ability of the BN compound forms a robust coating layer on the ZnO surface. This layer not only improves the dispersion stability of ZnO in polyurethane but also enhances interfacial bonding by forming strong hydrogen bonds with the matrix through phenolic hydroxyl groups and other groups. Simultaneously, tannic acid acts as a "bridge" to promote the interaction between ZnO and BN fillers, aiding in the construction of a more complete three-dimensional thermally conductive network. Overall, these two targeted surface modification strategies work together to address key issues such as poor filler-matrix compatibility, high interfacial thermal resistance, and easy filler agglomeration. Through fractal synergy and interfacial reinforcement design, highly interconnected and low-thermal-resistance thermally conductive pathways are constructed with low filler content, thereby significantly improving the thermal conductivity and overall reliability of the composite material.

[0016] The second technical solution of the present invention is a method for preparing the above-mentioned thermally conductive and protective polyurethane elastomer, comprising the following steps: The polyol and diisocyanate monomer were reacted under the action of a catalyst to obtain a polyurethane prepolymer. The polyurethane prepolymer, composite thermally conductive filler, and crosslinking agent are added to the solvent, and reaction 4 is carried out to obtain the thermally conductive and protective polyurethane elastomer.

[0017] In a preferred embodiment of the present invention, the polyol is polycaprolactone diol; the diisocyanate monomer is diphenylmethane diisocyanate; the catalyst is dibutyltin dilaurate; the mass ratio of the polyol, diisocyanate monomer and catalyst is 100:(6~10):(0.005~0.01); the temperature of reaction 3 is 80~95℃ and the time is 1~3h.

[0018] In a preferred embodiment of the present invention, the solvent is toluene; the crosslinking agent is triethylamine; the mass ratio of the polyurethane prepolymer to the crosslinking agent is 100:(0.04~0.08); the composite thermally conductive filler accounts for 10%~20% of the mass of the polyurethane elastomer; the temperature of the reaction 4 is 30~55℃, and the time is 7~14h.

[0019] The present invention discloses the following technical effects: 1. Significantly Improved Thermal Conductivity: A composite thermally conductive filler system is constructed using a polydopamine-silane coupling agent hybrid layer modified with lamellar boron nitride and tannic acid-modified spherical zinc oxide. These two components form a highly efficient and synergistic thermally conductive network within the polyurethane matrix. The lamellar BN readily overlaps horizontally within the matrix, forming a low-thermal-resistance planar thermally conductive main pathway. The spherical ZnO acts as "thermally conductive spheres," effectively filling the tiny voids inaccessible to the BN lamellars and bridging adjacent BN lamellars, upgrading the two-dimensional planar network to a three-dimensional interwoven network. This structure enables the formation of highly efficient thermally conductive pathways with lower filler content, allowing the composite material to achieve high thermal conductivity with a filler mass fraction of only 10%-20%, superior to single filler or simple blend systems.

[0020] 2. Enhanced filler dispersibility and interfacial compatibility: Polydopamine modification introduces active groups onto the boron nitride surface, while silane coupling agents further form a hybrid interfacial layer, enhancing the chemical bonding and interfacial adhesion between boron nitride and the polyurethane matrix. Tannic acid surface modification of zinc oxide also improves its compatibility with the matrix. This dual modification strategy effectively prevents filler agglomeration, promotes uniform dispersion within the matrix, and ensures the structural integrity and stability of the thermally conductive network.

[0021] 3. The thermally conductive and protective polyurethane elastomer provided by the present invention has high thermal conductivity and high strength. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0028] In this invention, the boron nitride flakes (BN, average particle size 15μm, thickness 0.5-1μm, industrial grade); the zinc oxide sphericals (ZnO, average particle size 0.5μm, industrial grade); and the polycaprolactone diol have a molecular weight of 2000-3000 g / mol.

[0029] In the examples, the preparation method of the sheet-like boron nitride modified by the polydopamine-silane coupling agent hybrid layer is as follows: S1. 10g of sheet-like boron nitride is dispersed in 300mL Tris-HCl buffer (pH=8.5), sonicated for 30min, then 2g of dopamine hydrochloride is added and stirred at room temperature for 24h, then the product is collected by centrifugation, washed and dried to obtain polydopamine modified boron nitride; S2. Disperse 10g of polydopamine-modified boron nitride in 300mL of ethanol aqueous solution (volume ratio 9:1), then add 0.2g of silane coupling agent KH-550, reflux at 80℃ for 6h, after the reaction is completed, collect the product, wash and dry it to obtain sheet-like boron nitride modified with polydopamine-silane coupling agent hybrid layer.

[0030] The preparation method of tannic acid modified spherical zinc oxide is as follows: 5.0 g ZnO is added to 200 mL of deionized water, ultrasonically dispersed for 1 h, pH is adjusted to 3, then 0.5 g tannic acid is added and stirred in a 60 °C water bath for 4 h. After the reaction is completed, the mixture is washed and dried to obtain tannic acid modified spherical zinc oxide.

[0031] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0032] Example 1 A method for preparing a thermally conductive and protective polyurethane elastomer, comprising the following steps: (1) Diphenylmethane diisocyanate, polycaprolactone diol and dibutyltin dilaurate (mass ratio of 100:7:0.008) were heated to 80°C in a nitrogen atmosphere and reacted for 1 h to obtain isocyanate-terminated polyurethane prepolymer. (2) Add isocyanate-terminated polyurethane prepolymer and composite thermally conductive filler (the mass ratio of lamellar boron nitride modified with polydopamine-silane coupling agent hybrid layer to spherical zinc oxide modified with tannic acid is 3:1) to toluene solvent, and then add triethylamine as a crosslinking agent. The mass ratio of polyurethane prepolymer, composite thermally conductive filler and triethylamine is 100:12:0.07. Heat to 30°C and react for 7 hours. Remove the solvent by vacuum distillation, wash with distilled water, and heat-press to mature to obtain thermally conductive and protective polyurethane elastomer.

[0033] Example 2 The only difference from Example 1 is that the mass ratio of polyurethane prepolymer, composite thermally conductive filler and triethylamine is 100:15:0.08. All other steps and parameters are the same as in Example 1.

[0034] Example 3 The only difference from Example 1 is that the mass ratio of polyurethane prepolymer, composite thermally conductive filler and triethylamine is 100:20:0.01. All other steps and parameters are the same as in Example 1.

[0035] Example 4 The only difference from Example 1 is that the mass ratio of the sheet-like boron nitride modified with the polydopamine-silane coupling agent hybrid layer to the spherical zinc oxide modified with tannic acid is 3:2. All other steps and parameters are the same as in Example 1.

[0036] Comparative Example 1 The only difference from Example 1 is that the sheet-like boron nitride modified with the polydopamine-silane coupling agent hybrid layer is replaced with unmodified boron nitride, and the tannic acid modified spherical zinc oxide is replaced with unmodified spherical zinc oxide. All other steps and parameters are the same as in Example 1.

[0037] Comparative Example 2 The only difference from Example 1 is that the tannic acid-modified spherical zinc oxide is omitted; all other steps and parameters are the same as in Example 1.

[0038] Performance testing: The thermal conductivity of the high-thermal-conductivity graphene-grafted polyurethane elastomer in the examples and comparative examples was tested using a TC-1200RH thermal conductivity tester, according to GB / T 3399-1982. The results are shown in Table 1.

[0039] The tensile strength of the highly thermally conductive graphene-grafted polyurethane elastomer was tested using a T150 UTM tensile testing instrument, according to GB / T 1040.1-2006. The results are shown in Table 2.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A thermally conductive and protective polyurethane elastomer, characterized in that, It includes a polyurethane matrix and a composite thermally conductive filler dispersed in the polyurethane matrix; The composite thermally conductive filler is a compound system of lamellar boron nitride modified with a polydopamine-silane coupling agent hybrid layer and spherical zinc oxide modified with tannic acid.

2. The thermally conductive and protective polyurethane elastomer according to claim 1, characterized in that, The composite thermally conductive filler accounts for 10% to 20% of the mass of the polyurethane elastomer.

3. The thermally conductive and protective polyurethane elastomer according to claim 1, characterized in that, The mass ratio of the sheet-like boron nitride modified with the polydopamine-silane coupling agent hybrid layer to the spherical zinc oxide modified with tannic acid is 3:(1~3).

4. The thermally conductive and protective polyurethane elastomer according to claim 1, characterized in that, The method for preparing the sheet-like boron nitride modified with a polydopamine-silane coupling agent hybrid layer includes the following steps: S1. Disperse the boron nitride flakes in Tris-HCl buffer, then add dopamine hydrochloride to react 1, to obtain polydopamine-modified boron nitride; S2. The polydopamine-modified boron nitride is dispersed in an aqueous ethanol solution, and then a silane coupling agent is added to carry out reaction 2 to obtain the sheet-like boron nitride modified with a polydopamine-silane coupling agent hybrid layer.

5. The thermally conductive and protective polyurethane elastomer according to claim 4, characterized in that, The pH of the Tris-HCl buffer solution is 8.5; the mass ratio of the boron nitride flakes to dopamine hydrochloride is 1:(0.1-0.3); the reaction 1 is carried out at room temperature for 12-24 hours under stirring; the average particle size of the boron nitride flakes is 15 μm and the thickness is 0.5-1 μm.

6. The thermally conductive and protective polyurethane elastomer according to claim 4, characterized in that, The silane coupling agent is KH-550; the mass ratio of the plate-shaped boron nitride to the silane coupling agent is 1:(0.15~0.3); the reaction 2 is a reflux reaction at 60~80℃ for 4~6h.

7. The thermally conductive and protective polyurethane elastomer according to claim 1, characterized in that, The method for preparing the tannic acid-modified spherical zinc oxide is as follows: ZnO is dispersed in water, the pH is adjusted, and then tannic acid is added to carry out reaction 3 to obtain the tannic acid-modified spherical zinc oxide.

8. The thermally conductive and protective polyurethane elastomer according to claim 7, characterized in that, The average particle size of the ZnO is 0.5 μm; the mass ratio of ZnO to tannic acid is 5:(0.5~1.5); the pH is 3~3.5; the reaction 3 is carried out by stirring at 50~60℃ for 2~4 hours.

9. The method for preparing the thermally conductive and protective polyurethane elastomer as described in claim 1, characterized in that, Includes the following steps: The polyol and diisocyanate monomer were reacted under the action of a catalyst to obtain a polyurethane prepolymer. The polyurethane prepolymer, composite thermally conductive filler, and crosslinking agent are added to the solvent, and reaction 4 is carried out to obtain the thermally conductive and protective polyurethane elastomer.

10. The preparation method according to claim 9, characterized in that, The polyol is polycaprolactone diol; the diisocyanate monomer is diphenylmethane diisocyanate; the catalyst is dibutyltin dilaurate; the mass ratio of the polyol, diisocyanate monomer and catalyst is 100:(6~10):(0.005~0.01); the temperature of reaction 3 is 80~95℃ and the time is 1~3h; The solvent is toluene; the crosslinking agent is triethylamine; the mass ratio of the polyurethane prepolymer to the crosslinking agent is 100:(0.04~0.08); the composite thermally conductive filler accounts for 10%~20% of the mass of the polyurethane elastomer; the temperature of reaction 4 is 30~55℃, and the time is 7~14h.

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