High-temperature resistant PET composite materials and their preparation methods

Abstract

This invention proposes a high-temperature resistant PET composite material, comprising: carbon nanotubes, silicone rubber, and PET prepolymer. By mass percentage, carbon nanotubes account for 25%–35%, silicone rubber for 20%–30%, and the remainder is PET prepolymer. The high-temperature resistant PET composite material has a planar orientation. The carbon nanotubes comprise multiple multi-walled carbon nanotube monomers, each with its axial direction parallel to the planar orientation, and the monomers are arranged intersectingly in the planar direction. This improves the impact resistance, heat resistance, and thermal insulation properties of the high-temperature resistant PET composite material.

Description

Technical Field

[0001] This invention belongs to the field of heat-resistant materials technology, and particularly relates to a high-temperature resistant PET composite material and its preparation method. Background Technology

[0002] Ceramic pistons typically possess low density and high strength, making them a promising candidate for applications in high-performance engines. Ceramic pistons can reduce the weight of piston assemblies, thereby reducing engine inertial load and improving fuel efficiency and power output.

[0003] However, ceramic pistons in related technologies are more fragile than metal pistons and are more susceptible to cracking due to external impacts or vibrations, which increases the risk in practical applications. Furthermore, the temperature inside the piston chamber of an engine is extremely high, and the thermal stress caused by the temperature gradient may lead to cracking or deformation of the piston surface, affecting its service life. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-temperature resistant PET composite material and its preparation method, which aims to solve the problems of insufficient impact resistance, heat resistance and heat insulation performance of ceramic pistons.

[0005] To address the aforementioned problems, this invention proposes a high-temperature resistant PET composite material, comprising: carbon nanotubes, silicone rubber, and PET prepolymer. By mass percentage, the carbon nanotubes comprise 25%–35%, the silicone rubber comprises 20%–30%, and the remainder is the PET prepolymer. The high-temperature resistant PET composite material has a planar orientation. The carbon nanotubes comprise multiple multi-walled carbon nanotube monomers, the axial direction of each multi-walled carbon nanotube monomer is parallel to the planar orientation, and the multi-walled carbon nanotube monomers are arranged intersectingly in the planar orientation.

[0006] In some embodiments of the present invention, the carbon nanotubes comprise a plurality of multi-walled carbon nanotube monomers, each of which has an outer diameter between 200 nm and 400 nm.

[0007] In some embodiments of the present invention, each of the multi-walled carbon nanotube monomers has an active functional group attached to its surface, the active functional group including at least one of hydroxyl, carboxyl, and silane groups.

[0008] This invention proposes a preparation method for preparing the high-temperature resistant PET composite material as described in any one of claims 1-3, characterized in that the steps include: S1. Modify the carbon nanotubes and prepare the PET prepolymer respectively; S2. The silicone rubber and the carbon nanotubes are added sequentially to the PET prepolymer for blending to obtain a high-temperature resistant mixture; S3. The high-temperature resistant mixture is coated on the surface of a substrate, and then the substrate is placed in a directional magnetic field to undergo magneto-orientation, thereby obtaining the high-temperature resistant PET composite material.

[0009] In some embodiments of the present invention, step S1, the step of preparing the carbon nanotubes includes: Preparation of modifying reagents; An appropriate amount of untreated multi-walled carbon nanotube monomer was added to the modifying agent and heated and stirred. An alkaline neutralizing agent is added to the reaction solution, and the solution is then filtered, washed, and dried to obtain the carbon nanotubes.

[0010] In some embodiments of the present invention, in step S1, the step of preparing the PET prepolymer includes: The ester component, alcohol component, and catalyst are heated in an inert atmosphere to generate a mixed component; The mixed components are placed in a pre-condensation reactor and a post-condensation reactor in sequence for condensation reaction to obtain the PET prepolymer.

[0011] In some embodiments of the present invention, the ester component includes ethylene terephthalate or butyl terephthalate, the alcohol component includes at least one of ethylene glycol, glycerol, and isopropanol, and the catalyst includes zinc acetate or cobalt acetate and antimony trioxide.

[0012] In some embodiments of the present invention, the surface of the substrate is provided with a plurality of intersecting microchannels, and each of the intersecting microchannels is arranged in a mesh pattern.

[0013] In some embodiments of the present invention, step S3, the step of placing the substrate in a directional magnetic field to achieve magneto-orientation, includes: The extension direction of each of the intersecting microchannels on the substrate is aligned with the magnetic field direction of the directional magnetic field. Vibrate the substrate to cause magneto-orientation of multiple multi-walled carbon nanotube monomers within the high-temperature resistant mixture; The substrate is placed in a heating chamber for curing.

[0014] In some embodiments of the present invention, the curing temperature is 80~120℃ and the curing time is 60~90min.

[0015] Compared with existing technologies, the high-temperature resistant PET composite material and its preparation method in this invention have the following advantages: This invention proposes a high-temperature resistant PET composite material, comprising: carbon nanotubes, silicone rubber, and PET prepolymer. By mass percentage, carbon nanotubes account for 25%~35%, silicone rubber accounts for 20%~30%, and the remainder is PET prepolymer. The high-temperature resistant PET composite material has a planar orientation. The carbon nanotubes include multiple multi-walled carbon nanotube monomers, the axial direction of each multi-walled carbon nanotube monomer is parallel to the planar orientation, and the multi-walled carbon nanotube monomers are arranged intersectingly in the planar orientation.

[0016] Both carbon nanotubes and silicone rubber possess heat-resistant properties. When added to PET prepolymer as heat-resistant fillers, the silicone rubber provides adhesive strength for bonding the high-temperature resistant PET composite material to the ceramic piston. Crosslinking enhances the interlayer bonding force between different components in the ceramic material. The crosslinking of silicone rubber and carbon nanotubes with the PET prepolymer forms a denser network structure, which can effectively absorb energy under external forces, reducing impact and stress on the ceramic material, thereby enhancing its impact resistance. Due to the difference in the axial (along the pipe axis) and circumferential (perpendicular to the pipe axis) lattice structures of carbon nanotubes, their axial and circumferential thermal conductivity differs. The circumferential thermal conductivity of multi-walled carbon nanotube monomers is much lower than that along the axial direction, further reducing the thermal conductivity of the high-temperature resistant PET composite material and improving its thermal insulation performance. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of a method for preparing high-temperature resistant PET composite material in one embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] This invention proposes a high-temperature resistant PET composite material, comprising: carbon nanotubes, silicone rubber and PET prepolymer, wherein, by mass percentage, carbon nanotubes account for 25% to 35%, silicone rubber accounts for 20% to 30%, and the remainder is PET prepolymer.

[0020] Carbon nanotubes possess a highly stable crystalline structure with a highly ordered lattice arrangement, enabling them to maintain stability at high temperatures and resist structural changes or melting. Their extremely high specific surface area results in low heat exchange efficiency with the surrounding environment, meaning they can better maintain a relatively stable internal temperature under high-temperature conditions and are less susceptible to external heat. Silicone rubber exhibits weak interactions between its molecular chains and low intermolecular friction. Therefore, under high-temperature conditions, the molecular chains of silicone rubber do not undergo large-scale movement, giving it strong heat resistance.

[0021] Carbon nanotubes and silicone rubber are added to PET prepolymer as heat-resistant fillers. Silicone rubber contains functional groups such as silicon-hydrogen bonds or silicon-oxygen bonds, which react chemically with the hydroxyl or carboxyl groups in the PET prepolymer to form a cross-linked structure. This cross-linked structure provides multiple intermolecular hydrogen bonding sites. Through these intermolecular hydrogen bonds, carbon nanotubes and silicone rubber are blended with the PET prepolymer, resulting in a tight bond between them and the PET prepolymer, effectively enhancing the structural stability of the high-temperature resistant PET composite material.

[0022] Meanwhile, silicone rubber also provides adhesive strength for the bonding of high-temperature resistant PET composite materials and ceramic pistons. Silicone rubber has good adhesion properties, can adhere to the surface of ceramic pistons, and fill the microscopic unevenness of the surface, forming good contact with high-temperature resistant PET composite materials, thereby improving the bonding strength.

[0023] To improve the surface strength of ceramic pistons, PET prepolymer is used as the base material. PET possesses excellent mechanical properties, including high strength, high stiffness, and good wear resistance, providing good mechanical support and enhancing the strength of the ceramic piston. The crosslinking between silicone rubber and carbon nanotubes with the PET prepolymer enhances their interfacial interaction within the ceramic material. This enhanced interfacial interaction effectively transfers stress and energy, thereby improving the overall strength of the ceramic material.

[0024] Crosslinking enhances the interlayer bonding between different components in ceramic materials. The crosslinking of silicone rubber and carbon nanotubes with PET prepolymer forms a denser network structure, allowing the components within the material to bind more tightly together, thereby improving the overall strength of the material. Silicone rubber and carbon nanotubes, with their excellent elasticity and energy absorption capabilities, can effectively absorb energy under external forces, reducing impact and stress on ceramic materials and thus enhancing their impact resistance. Crosslinking can improve the grain structure of ceramic pistons, making it more uniform and dense. This grain structure not only improves the strength of ceramic pistons but also reduces microcracks and defects in the material, enhancing the overall strength performance of the ceramic piston.

[0025] Furthermore, the high-temperature resistant PET composite material has a planar orientation, with the axial direction of each multi-walled carbon nanotube monomer parallel to the planar orientation, and the multi-walled carbon nanotube monomers are arranged intersectingly in the planar orientation. The heat transfer direction of the ceramic piston coated with the high-temperature resistant PET composite material is along the thickness direction of the high-temperature resistant PET composite material. Multiple parallel multi-walled carbon nanotube monomers are arranged at intervals along the thickness direction of the high-temperature resistant PET composite material, so heat transfer occurs along the circumference of each multi-walled carbon nanotube monomer.

[0026] The axial (along the pipe axis) and circumferential (perpendicular to the pipe axis) lattice structures of carbon nanotubes differ. The axial lattice structure is typically more regular, while the circumferential lattice structure is more complex, containing numerous twists and defects. This structural difference leads to different thermal conductivity along the axial and circumferential directions. The circumferential thermal conductivity of multi-walled carbon nanotube monomers is much lower than that along the axial direction. Therefore, this further reduces the thermal conductivity of the high-temperature resistant PET composite material, improves the thermal insulation performance of the ceramic piston, reduces the heat transferred to the surface of the ceramic piston, and decreases the temperature difference between the piston and the environment. This effectively converts heat into the kinetic energy required for piston movement, thereby improving the piston's energy conversion efficiency. It also effectively reduces fuel consumption, improves engine fuel efficiency, and lowers operating costs.

[0027] Meanwhile, multiple multi-walled carbon nanotube monomers intersecting in the planar direction of the high-temperature resistant PET composite material form a cross-linked network structure, which effectively enhances the structural strength of the high-temperature resistant PET composite material and improves the wear resistance of the ceramic piston surface.

[0028] Specifically, carbon nanotubes consist of multiple multi-walled carbon nanotube monomers, each with an outer diameter between 200 nm and 400 nm. Ceramic pistons operate within the engine chamber, which generates significant heat. If the material coated on the ceramic piston has excessively high thermal conductivity, heat will be rapidly conducted to the piston surface, increasing heat loss and affecting piston efficiency. Thermal stress caused by temperature gradients during piston operation can lead to cracking or deformation of the piston surface, impacting its lifespan. Coatings with low thermal conductivity can mitigate temperature gradient changes, reduce thermal stress, and improve piston stability and durability.

[0029] Therefore, the carbon nanotubes selected in the high-temperature resistant PET composite material coated on the ceramic piston are multi-walled carbon nanotubes. Multi-walled carbon nanotubes are formed by rolling up multiple layers of graphite sheets. There are gaps and relative sliding possibilities between the layers. The interaction between these gaps and sliding layers slows down the propagation speed of heat, thereby reducing the overall thermal conductivity of multi-walled carbon nanotubes.

[0030] Multi-walled carbon nanotubes (MWCNTs) have a complex internal structure with numerous scattering centers at the interfaces between layers, such as grain boundaries and interlayer defects. This interfacial scattering causes repeated scattering of heat particles between layers, reducing heat transfer efficiency and slowing down heat conduction. Larger diameter MWCNTs indicate more layers, further hindering heat transfer. Outer diameters of the outer wall carbon nanotubes can be 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm. Different diameters are selected and added to high-temperature resistant PET composites based on application requirements to reduce the thermal conductivity of the PET composite. Furthermore, silicone rubber contains numerous silicon-oxygen (Si-O) bonds in its molecular structure. These non-metallic bonds exhibit strong scattering during heat conduction due to their vibrational modes, thus reducing thermal conductivity. Silicone rubber also possesses numerous micropores and voids, which further impede heat propagation, thereby reducing the thermal conductivity of high-temperature resistant PET composites.

[0031] In one embodiment of the present invention, the surface of each multi-walled carbon nanotube monomer is connected with active functional groups, including at least one of hydroxyl, carboxyl, and aldehyde groups. Functionalization of the carbon nanotube surface can increase its compatibility with silicone rubber and PET prepolymers and facilitate the formation of cross-linked structures. Oxidation treatment of the carbon nanotube surface introduces active functional groups such as carboxyl, hydroxyl, and silane groups, enabling it to form more hydrogen bonds or chemical bonds with silicone rubber or PET, thereby enhancing their adhesion and cross-linking.

[0032] The modified carbon nanotubes with functional groups have the cross-linking effect of coupling agents, eliminating the need to add other coupling agents, such as peroxide-based coupling agents or epoxy-based coupling agents, to the high-temperature resistant PET composite material. Coupling agents will remain in the material, leading to unstable performance of the high-temperature resistant PET composite material and affecting its service life. By not adding other coupling agents, this problem can be avoided, ensuring the stability and durability of the material.

[0033] Example 1: Please refer to Figure 1 Example 1 of the present invention proposes a preparation method for preparing high-temperature resistant PET composite materials, the steps of which include: S1. Modify carbon nanotubes and prepare PET prepolymers respectively.

[0034] The steps involved in modifying carbon nanotubes include: Modifying agents were prepared, including nitric acid, sulfuric acid, and potassium permanganate. These agents acted as strong modifiers to introduce functional groups, with a ratio of 1:3:1. These agents introduced hydroxyl and carboxyl functional groups onto the surface of carbon nanotubes, increasing their chemical activity and enabling them to react with different materials, such as through cross-linking and functionalization. This improved the bonding performance between high-temperature resistant PET composites and ceramic materials.

[0035] An appropriate amount of untreated multi-walled carbon nanotube monomer was added to the modifying reagent, and the mixture was heated and stirred. Under heating conditions, the modifying reagent reacted with the carbon nanotubes to undergo an oxidation reaction, oxidizing the carbon atoms on the surface of the carbon nanotubes into specific functional groups. The heating temperature was 60℃, and the stirring time was 90 min. The reaction equations for the carbon nanotubes (CNTs) and the components of the modifying reagent are shown below: CNT + HNO3 → CNT-OH / CNT-COOH + NO x +H2O; CNT+H2SO4→CNT-OH / CNT-COOH+SO2+H2O; CNT+KMnO4+H + →CNT-OH / CNT-COOH+CO2+MnO2+K + +H2O; This results in the formation of carbon nanotubes with hydroxyl and carboxyl functional groups.

[0036] An alkaline neutralizing agent is added to the reaction solution, and the solution is then filtered, washed, and dried to obtain carbon nanotubes.

[0037] A basic neutralizing agent, such as sodium bicarbonate solution, neutralizes the acidic modifying agent in the solution, bringing it to neutral or near-neutral levels. This avoids the influence of acidic conditions on subsequent experimental steps or product properties. It also effectively reduces the occurrence of these side reactions, improving reaction selectivity and product purity.

[0038] The carbon nanotubes were washed with deionized water, and then centrifuged. Because carbon nanotubes are small in size and mass, traditional filtration methods can lead to mass reduction or incomplete filtration. Centrifugation effectively solves these problems. The samples were then washed multiple times with deionized water to remove residual modifying agents and other impurities. Finally, the washed carbon nanotube samples were dried, either using vacuum drying or low-temperature drying methods.

[0039] The steps for preparing PET prepolymer include: An ester component, an alcohol component, and a catalyst are heated in an inert atmosphere to generate a mixed component. The ester component includes polyethylene terephthalate, the alcohol component includes ethylene glycol, and the catalyst includes zinc acetate and antimony trioxide. The molar ratio of the ester component to the alcohol component is 1:1.2~1.5, and the mass percentage of the catalyst in the alcohol component is 0.01%~0.05%. In Example 1, the molar ratio of polyethylene terephthalate to ethylene glycol is 1:1.3, and the mass percentage of the catalyst is 0.02%. The inert atmosphere can be nitrogen, argon, helium, etc.

[0040] The mixed components were sequentially placed in a pre-polymerization reactor and a post-polymerization reactor for polymerization to obtain a PET prepolymer. The reaction temperature in the pre-polymerization reactor was 270°C, and the reaction temperature in the post-polymerization reactor was 280°C. The higher temperature in the post-polymerization reactor helps to increase the polymerization rate, thereby accelerating the growth of polymer chains. This ensures that the desired polymer molecular weight is obtained in subsequent processing. The high temperature also reduces the viscosity of the polymer, making the polymerization reaction smoother. This helps to ensure the continuity and consistency of the polymer chains. Moreover, a certain degree of heat helps to promote the crystallization process of PET molecular chains. Increased crystallinity can improve physical properties such as strength and stiffness.

[0041] After undergoing a polycondensation reaction, dimethyl terephthalate and ethylene glycol are linked together by ester bonds to form a linear polymer. The cross-linking of this linear polymer creates numerous cavities, providing space for subsequent blending of heat-resistant fillers. The cross-linked network structure effectively enhances the tensile strength and structural strength of the high-temperature resistant PET composite material.

[0042] S2. Silicone rubber and carbon nanotubes are added sequentially to the PET prepolymer for blending to obtain a high-temperature resistant mixture. The carbon nanotubes are first stirred with the PET prepolymer before adding the silicone rubber to the mixture. Silicone rubber has a lower fluid viscosity; adding the carbon nanotubes to the PET prepolymer first facilitates the subsequent addition of silicone rubber and also promotes the uniform dispersion of the carbon nanotubes in the mixture. The carbon nanotubes comprise 35%, the silicone rubber 30%, and the remainder is PET prepolymer.

[0043] S3. The high-temperature resistant mixture is coated on the surface of the substrate, and then the substrate is placed in a directional magnetic field to achieve magneto-orientation. After curing, the high-temperature resistant PET composite material is obtained.

[0044] The steps of placing the substrate in a directional magnetic field to achieve magneto-oriented alignment include: The extension direction of each intersecting microchannel on the substrate is aligned with the direction of the directional magnetic field. Carbon nanotubes are honeycomb structures composed of carbon atoms, forming hollow cylindrical structures. In this structure, the arrangement and axial configuration of carbon atoms give carbon nanotubes certain magnetic dipole properties. When an external magnetic field is applied to carbon nanotubes, due to the special shape and electronic structure of carbon nanotubes, their internal spin and charge distribution are affected by the magnetic field. If the direction of the external magnetic field is aligned with the axis of the carbon nanotube, the magnetic field will further enhance or adjust the spin orientation of the electrons inside the carbon nanotube, making the carbon nanotube as a whole exhibit magnetism and displaying magnetic dipole properties in the same direction as the external magnetic field, resulting in the axis of the carbon nanotube being in the same direction as the direction of the directional magnetic field.

[0045] Therefore, taking advantage of this property of carbon nanotubes, the carbon nanotubes coated on the substrate rotate in the same direction as or close to the magnetic field of the directional magnetic field, thus keeping the carbon nanotubes parallel to the surface of the substrate. Heat is transferred from the external environment to the surface of the substrate along the thickness direction of the high-temperature resistant PET composite material, that is, the heat transfer direction is along the circumference of the carbon nanotubes. The circumferential thermal conductivity of carbon nanotubes is lower, which effectively enhances the heat resistance and thermal insulation properties of the high-temperature resistant PET composite material.

[0046] Vibrating the substrate causes multiple multi-walled carbon nanotube monomers within the high-temperature resistant mixture to undergo magneto-orientation. The substrate surface has multiple intersecting microchannels arranged in a mesh pattern. These intersecting microchannels assist in guiding the carbon nanotubes, promoting their intersecting arrangement, and enhancing the wear resistance of the high-temperature resistant PET composite material.

[0047] The substrate was placed in a heating chamber for curing at a temperature of 80°C for 60 minutes.

[0048] If the heating temperature is too high, the substrate and the high-temperature resistant PET composite material will over-melt during the drying process, resulting in uneven surfaces and even cracks or bubbles. It will also cause volatile components to evaporate too quickly during the reaction, leading to insufficient formation of the pore structure in the material and reducing its density and mechanical properties.

[0049] If the temperature is too low, the substrate and high-temperature resistant PET composite material will not dry and cure completely, resulting in unreacted or uncured parts on the surface or inside of the material, which will reduce the mechanical properties and stability of the material.

[0050] If the curing time is too long, the high-temperature resistant PET composite material will become over-hardened, making the material brittle and reducing its toughness and impact resistance. If the curing time is too short, the high-temperature resistant PET composite material will not cure completely, leaving unreacted or uncured parts on the surface or inside the material. This will affect the mechanical properties and stability of the material, and may lead to unstable performance, making it susceptible to changes caused by external environmental factors.

[0051] Example 2: Example 2 of the present invention proposes a preparation method for preparing high-temperature resistant PET composite materials, the steps of which include: S1. Modify carbon nanotubes and prepare PET prepolymers respectively.

[0052] The steps involved in modifying carbon nanotubes include: A modifying agent is prepared, which includes trichlorosilane, which introduces silane groups onto the carbon nanotubes.

[0053] An appropriate amount of untreated multi-walled carbon nanotube monomer was added to the modifying agent, and the mixture was heated and stirred at 60°C for 90 minutes.

[0054] An alkaline neutralizing agent is added to the reaction solution, and the solution is then filtered, washed, and dried to obtain carbon nanotubes. The alkaline neutralizing agent is a sodium bicarbonate solution.

[0055] The steps for preparing PET prepolymer include: The ester component, alcohol component, and catalyst are heated in an inert atmosphere to generate a mixed component; wherein the ester component includes butyl terephthalate, the alcohol component includes glycerol, and the catalyst includes cobalt acetate and antimony trioxide; the molar ratio of butyl terephthalate to glycerol is 1:1.5, and the mass percentage of the catalyst is 0.05%.

[0056] The mixed components were placed in a pre-condensation reactor and a post-condensation reactor in sequence for condensation reaction to obtain PET prepolymer. The reaction temperature of the pre-condensation reactor was 270℃ and the reaction temperature of the post-condensation reactor was 280℃.

[0057] S2. Silicone rubber and carbon nanotubes are added sequentially to the PET prepolymer for blending to obtain a high-temperature resistant mixture. The carbon nanotubes account for 25%, the silicone rubber accounts for 30%, and the balance is PET prepolymer.

[0058] S3. The high-temperature resistant mixture is coated on the surface of the substrate, and then the substrate is placed in a directional magnetic field to achieve magneto-orientation. After curing, the high-temperature resistant PET composite material is obtained.

[0059] The steps of placing the substrate in a directional magnetic field to achieve magneto-oriented alignment include: The extension direction of each intersecting microchannel on the substrate is set to be in the same direction as the magnetic field direction of the directional magnetic field; Vibrate the substrate to induce magneto-orientation of multiple multi-walled carbon nanotube monomers within the high-temperature resistant mixture; The substrate was placed in a heating chamber for curing at a temperature of 100°C for 90 minutes.

[0060] Comparative Example 1: The difference between the preparation method of the high-temperature resistant PET composite material in Comparative Example 1 and Example 1 is that the carbon nanotubes were not modified in step S1.

[0061] Comparative Example 2: The difference between the preparation method of the high-temperature resistant PET composite material in Comparative Example 2 and Example 1 is that, in step S2, the mass percentage of carbon nanotubes is 50%. Comparative Example 3: The difference between the preparation method of the high-temperature resistant PET composite material in Comparative Example 3 and Example 1 is that the mass ratio of carbon nanotubes in step S2 is 10%.

[0062] Comparative Example 4: The difference between the preparation method of the high-temperature resistant PET composite material in Comparative Example 4 and Example 1 is that the substrate was not placed in a directional magnetic field to achieve magneto-orientation during step S3.

[0063] Experiment 1: Determination of thermal conductivity of high temperature resistant PET composite material.

[0064] The thermal conductivity of the high-temperature resistant PET composite materials obtained in Examples 1-2 and Comparative Examples 1-4 was measured using a thermal conductivity measuring instrument. During the experiment, a release film was used as the substrate to facilitate the separation and cutting of the high-temperature resistant PET composite material into test pieces, which were then placed in the thermal conductivity measuring instrument. The test temperature and test time for thermal conductivity were set, and the calculation formula was φ=-λA*(dt / dx), where φ is the heat flow rate, λ is the thermal conductivity, A is the area of ​​the test piece, and t is the test time.

[0065] Table 1. Comparison of thermal conductivity of various embodiments and comparative examples: According to Table 1 above: Examples 1 and 2, as well as Comparative Examples 1 and 3, all exhibit low thermal conductivity, demonstrating strong heat insulation and heat resistance properties. However, Comparative Example 2 contains excessive carbon nanotubes, which negatively impacts the thermal insulation capability of the high-temperature resistant PET composite material. In Comparative Example 4, the carbon nanotubes were not magnetooriented in a directional magnetic field, making it difficult for the multiple multi-walled carbon nanotube monomers to be aligned parallel to the surface of the high-temperature resistant PET composite material, resulting in a decrease in heat insulation and heat resistance properties in localized areas.

[0066] Experiment 2: Tensile test of high temperature resistant PET composite material.

[0067] The high-temperature resistant PET composite materials prepared in Examples 1-2 and Comparative Examples 1-4 were placed in a tensile testing machine for tensile testing. During the test, a release film was used as the substrate to facilitate the separation and cutting of the high-temperature resistant PET composite material into test pieces. The tensile direction of the test pieces was along the plane of the high-temperature resistant PET composite material.

[0068] Table 2. Comparison of elastic modulus of each embodiment and comparative example: According to Table 2 above: The elastic modulus of the high-temperature resistant PET composite materials in Examples 1-2 is much higher than that of the comparative examples 1-4, indicating that the high-temperature resistant PET composite materials prepared using the preparation method of the present invention have a very high elastic modulus. When coated on ceramic pistons, they have strong wear resistance and impact resistance.

[0069] In Comparative Example 1, the carbon nanotubes were not modified in step S1. The carbon nanotubes could not function as coupling agents, making it difficult for them to crosslink with silicone rubber and PET prepolymer. Furthermore, the internal distribution of the components was not uniform, resulting in a significant decrease in the elastic modulus.

[0070] In Comparative Example 2, the mass percentage of carbon nanotubes in step S2 is 50%. An excessively high mass percentage of carbon nanotubes leads to an increase in the viscosity of the high-temperature resistant PET composite material, resulting in carbon nanotube aggregation and a significant decrease in the elastic modulus.

[0071] In Comparative Example 3, the mass percentage of carbon nanotubes in step S2 is 10%. If the mass percentage of carbon nanotubes is too small, there is too little internal support structure, making it difficult to form an effective cross-linked network structure, resulting in a decrease in elastic modulus.

[0072] In Comparative Example 4, the substrate was not placed in a directional magnetic field to achieve magneto-orientation during step S3. The circumferential direction of the carbon nanotubes was difficult to align with the thickness direction of the high-temperature resistant PET composite material, and without microchannels to guide the multiple multi-walled carbon nanotube monomers, it was difficult to form an effective cross-linked network structure, resulting in a decrease in elastic modulus.

[0073] In one embodiment of the present invention, a ceramic piston is also provided, wherein the outer surface of the ceramic piston is coated with a high-temperature resistant PET composite material.

[0074] The specific steps are as follows: The high-temperature resistant mixture is applied to the outer surface of the ceramic piston by spraying or brushing. The silicone rubber in the high-temperature resistant mixture acts as a binder, enhancing the adhesion between the high-temperature resistant PET composite material and the ceramic piston. In other embodiments, the surface of the ceramic piston can be modified with active groups, which can also enhance the adhesion between the high-temperature resistant PET composite material and the ceramic piston.

[0075] The ceramic piston was then magnetooriented and cured to obtain a ceramic piston coated with a high-temperature resistant PET composite material. Since the ceramic piston is non-magnetic, only the multi-walled carbon nanotube monomers in the high-temperature resistant PET composite material are affected by the magnetic field.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high temperature resistant PET composite material, characterized in that, include: The carbon nanotubes, silicone rubber, and PET prepolymer are, by mass percentage, wherein the carbon nanotubes account for 25% to 35%, the silicone rubber accounts for 20% to 30%, and the remainder is the PET prepolymer. The high-temperature resistant PET composite material has a planar orientation. The carbon nanotubes include multiple multi-walled carbon nanotube monomers, the axial direction of each multi-walled carbon nanotube monomer is parallel to the planar orientation, and the multi-walled carbon nanotube monomers are arranged intersectingly in the planar orientation. The steps in the preparation method of high-temperature resistant PET composite materials include: S1. Modify the carbon nanotubes and prepare the PET prepolymer respectively; The steps for preparing the carbon nanotubes include: Prepare a modifying agent, which includes at least one of nitric acid, sulfuric acid, potassium permanganate, and trichlorosilane; An appropriate amount of untreated multi-walled carbon nanotube monomer was added to the modifying agent and heated and stirred. An alkaline neutralizing agent is added to the reaction solution, and the solution is then filtered, washed, and dried to obtain the carbon nanotubes. S2. The silicone rubber and the carbon nanotubes are added sequentially to the PET prepolymer for blending to obtain a high-temperature resistant mixture; S3. The high-temperature resistant mixture is coated on the surface of the substrate, and then the substrate is placed in a directional magnetic field to undergo magneto-orientation. After curing, the high-temperature resistant PET composite material is obtained. The step of placing the substrate in a directional magnetic field to achieve magneto-orientation includes: The extension direction of each of the intersecting microchannels on the substrate is aligned with the magnetic field direction of the directional magnetic field. Vibrate the substrate to cause magneto-orientation of multiple multi-walled carbon nanotube monomers within the high-temperature resistant mixture; The substrate is placed in a heating chamber for curing.

2. The high temperature resistant PET composite material of claim 1, wherein, The outer diameter of each of the multi-walled carbon nanotube monomers is between 200 nm and 400 nm.

3. The high temperature resistant PET composite material of claim 2, wherein, Each of the multi-walled carbon nanotube monomers has an active functional group attached to its surface, the active functional group including at least one of hydroxyl, carboxyl, and silane groups.

4. The high-temperature resistant PET composite material according to claim 1, characterized in that, The surface of the substrate is provided with multiple intersecting microchannels, and each intersecting microchannel is arranged in a mesh pattern.

5. The high-temperature resistant PET composite material according to claim 1, characterized in that, The curing temperature is 80~120℃, and the curing time is 60~90min.

6. A method for preparing a high-temperature resistant PET composite material, used to prepare the high-temperature resistant PET composite material as described in any one of claims 1-5, characterized in that, The steps in the preparation method of high-temperature resistant PET composite materials include: S1. Modify the carbon nanotubes and prepare the PET prepolymer respectively; S2. The silicone rubber and the carbon nanotubes are added sequentially to the PET prepolymer for blending to obtain a high-temperature resistant mixture; S3. The high-temperature resistant mixture is coated on the surface of the substrate, and then the substrate is placed in a directional magnetic field to undergo magneto-orientation. After curing, the high-temperature resistant PET composite material is obtained. The steps for preparing the PET prepolymer include: The ester component, alcohol component, and catalyst are heated in an inert atmosphere to generate a mixed component; The mixed components are placed in a pre-condensation reactor and a post-condensation reactor in sequence for condensation reaction to obtain the PET prepolymer.

7. The preparation method according to claim 6, characterized in that, The ester component includes ethylene terephthalate or butyl terephthalate, the alcohol component includes at least one of ethylene glycol, glycerol, and isopropanol, and the catalyst includes zinc acetate or cobalt acetate and antimony trioxide.

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