A PET elastomer, composite material, dynamic covalent network polymer, its preparation method and application

Abstract

This application relates to the field of polymer materials technology, providing a PET elastomer, composite material, dynamic covalent network polymer, and its preparation method and application. The elastomer is prepared by in-situ self-assembly of crown ether-primary amide dual-functionalized PET through melt blending. Its molecular network integrates a quasi-rotaxane supramolecular crosslinking network. This structure is formed by the host-guest interaction between the crown ether and the primary amide, and can act as a sliding crosslinking point to dissipate energy through the sliding of cyclic components. This application employs a two-step end-capping-in-situ self-assembly process to overcome the technical obstacles of low PET chain-end activity and poor compatibility between polyrotaxane and PET, achieving molecular-level dispersion of quasi-rotaxane in the PET matrix. This fully utilizes the molecular pulley effect to achieve breakthrough toughening of the elastomer. Simultaneously, it combines rigid nanofillers modified with aminosilane coupling agents to form a soft-hard synergistic network, enabling the PET composite material to maintain high toughness while simultaneously improving strength, modulus, and thermal properties.

Description

Technical Field

[0001] This application belongs to the field of polymer materials technology, and particularly relates to a PET elastomer, composite material, dynamic covalent network polymer, and its preparation method and application. Background Technology

[0002] Polyethylene terephthalate (PET) is a thermoplastic polyester with excellent overall performance. Due to its good mechanical properties, high chemical stability, low cost, and good processability, it is widely used in fibers, bottle packaging, and engineering plastics. However, PET's inherent brittleness and low impact toughness limit its application in high-end fields. Traditional PET toughening methods mainly involve blending with rubber, acrylate elastomers, etc. While this can slightly improve toughness, it significantly sacrifices the material's strength, flexural modulus, and heat distortion temperature. Furthermore, the modified blends suffer from poor compatibility and are difficult to recycle, placing a significant burden on the environment.

[0003] In recent years, mechanically interlocked molecules (MIMs) such as polyrotaxane and quasi-rotaxane have provided a novel approach to toughening polymer materials. Their cyclic molecules can slide freely along linear molecular axes, dissipating energy through the "molecular pulley effect," significantly improving the toughness, elongation at break, and self-healing properties of polymers. They have been successfully applied to the toughening modification of elastomers such as polyurethane. However, introducing polyrotaxane / quasi-rotaxane structures into the semi-crystalline engineering plastic PET still faces two major, non-obvious technical obstacles: first, PET chain-end chemical inertness results in a single functional group and few reaction sites after melt polycondensation, making it difficult to directly graft functional molecules such as crown ethers and amides; second, the polarity mismatch between polyrotaxane and PET leads to macroscopic phase separation and stress defect points during direct blending, hindering the toughening effect. Currently, there are no reports of successfully introducing polyrotaxane / quasi-rotaxane structures into PET systems and achieving synergistic improvements in toughness, strength, and recyclability. Therefore, developing a novel PET-modified material and its preparation method to resolve the technical contradictions of traditional PET toughening has significant industrial and environmental value. Summary of the Invention

[0004] The purpose of this application is to provide an adaptive PET elastomer, which aims to solve the technical problems of the contradiction between toughness improvement and strength and modulus maintenance in traditional PET toughening technology, the difficulty in effectively introducing polyrotaxane / quasi-rotaxane mechanical interlocking structure into the PET system due to the inertness of PET chain ends and the mismatch with PET polarity, and the poor compatibility and recyclability of traditional PET modified materials.

[0005] The embodiments of this application are implemented as follows: an adaptive PET elastomer is prepared by melt blending and in-situ self-assembly of end-functionalized PET. The end-functionalized PET is a PET molecular chain with one end modified with a crown ether group and the other end modified with a primary amide group. The PET molecular network of the adaptive PET elastomer integrates a quasi-rotaxane supramolecular crosslinking network. The quasi-rotaxane structure in this network is formed by the self-assembly of the crown ether group and the primary amide group of the end-functionalized PET through host-guest interaction. The quasi-rotaxane structure acts as a sliding crosslinking point and can dissipate energy through the sliding motion of the cyclic components.

[0006] Another objective of this application is a method for preparing an adaptive PET elastomer as described above, comprising: a) Hydroxyl-terminated PET prepolymer was prepared by melt polycondensation; b) By introducing crown ether groups and amide groups into both ends of PET prepolymer through a two-step isocyanate / acyl chloride end-capping reaction, terminal functionalized PET is obtained; c) The end-functionalized PET is melt-blended at 240-280°C and 50-200 rpm, and a quasi-rotaxane crosslinking network is formed through host-guest recognition of crown ether-amide, resulting in an adaptive PET elastomer.

[0007] Another objective of this application is to provide a PET composite material, which is prepared by melt blending the aforementioned end-functionalized PET with a rigid nanofiller modified by an aminosilane coupling agent to form a soft-hard composite network in which a quasi-rotaxane supramolecular network and a rigid nanofiller work together.

[0008] Another objective of this application is to provide a method for preparing the PET composite material as described above, including steps a) and b) as described above, and further comprising: d) Surface modification of rigid nanofillers: Rigid nanofillers were ultrasonically dispersed in ethanol, glacial acetic acid was added, the pH value was adjusted to 5.0, and then 1 wt% of aminosilane coupling agent relative to the total mass of the filler was added. The mixture was refluxed at 70°C for 6 h, and after centrifugation, washing and drying, the modified rigid nanofillers were obtained. e) Melt blending molding: The end-functionalized PET from step b) is premixed with the modified rigid nanofiller from step d), and then melt-blended and extruded in a twin-screw extruder at 240-280℃ and 50-200rpm to obtain a PET composite material.

[0009] Another objective of this application is to provide a PET-based dynamic covalent network polymer, which is obtained by melt molding of end-functionalized PET containing dynamic covalent bonds, forming a dual network structure of quasi-rotaxane physical crosslinking and dynamic covalent chemical crosslinking; wherein the dynamic covalent bonds are disulfide bonds or ester bonds that can catalyze transesterification.

[0010] Another objective of this application is a method for preparing a PET-based dynamic covalent network polymer as described above, comprising: Option 1: Prepare a polymer containing disulfide bonds: a1) Preparation of hydroxyl-terminated PET prepolymer containing disulfide bonds: In the melt polycondensation stage of step a) of claim 3, dithiodibenzoic acid, accounting for 5% of the total molar amount of diacid, is introduced and co-condensed with terephthalic acid and ethylene glycol to obtain a hydroxyl-terminated PET prepolymer with disulfide bonds in the main chain. b1) Perform end-group functionalization on the hydroxyl-terminated PET prepolymer containing disulfide bonds according to the method in step b) above to obtain end-group functionalized PET containing disulfide bonds. c3) The end-functionalized PET containing disulfide bonds is melt-molded at 240-280℃ and 50-200rpm to obtain a polymer with a dual network structure; Alternatively, in option two, a polymer containing catalytically exchangeable ester bonds can be prepared: a2) Preparation of hydroxyl-terminated PET prepolymer containing secondary hydroxyl groups: Glycerol is added to provide secondary hydroxyl groups during the melt polycondensation stage of step a) in claim 3 to obtain hydroxyl-terminated PET prepolymer containing secondary hydroxyl groups; b2) Perform end-group functionalization according to the method in step b) above to obtain end-group functionalized PET containing secondary hydroxyl groups; c2) The terminal functionalized PET containing secondary hydroxyl groups is mixed with 0.5wt% zincate catalyst and melt-molded at 240-280℃ and 50-200rpm to obtain a polymer with a dual network structure.

[0011] Another objective of this application is the application of the above-described adaptive PET elastomer, the above-described PET composite material, and the above-described PET-based dynamic covalent network polymer in the preparation of flexible electronic devices, engineering plastics, or recyclable packaging materials.

[0012] This application's embodiments successfully overcome two non-obvious technical obstacles—low PET chain-end activity and poor compatibility due to the polarity mismatch between polyrotaxane and PET—through an original two-step end-capping-in-situ self-assembly process. This achieves molecular-level dispersion of quasi-rotaxane in the PET matrix and fully utilizes the molecular pulley effect of the sliding cyclic components. This results in a breakthrough in toughening of the prepared adaptive PET elastomer, with a notched impact strength reaching up to 60.5 kJ / m. 2With an elongation at break exceeding 500%, and through the formation of a soft-hard synergistic network using rigid nanofillers modified with aminosilane coupling agents, PET composites achieve simultaneous improvements in strength, modulus, and thermal properties while maintaining high toughness. The tensile strength reaches a maximum of 72 MPa, and the heat distortion temperature exceeds 100℃, completely resolving the industry pain point that traditional PET toughening technologies inevitably sacrifice strength and modulus for toughness enhancement. Simultaneously, disulfide bonds and catalytic ester exchange bonds are introduced into the PET-based dynamic covalent network polymer to construct a dual-network structure, achieving a closed-loop chemical recovery rate of over 90% for catalytic depolymerization monomers. Furthermore, various PET modifications... After three melting and regranulation processes, the intrinsic viscosity of the product remains at no less than 85%, significantly improving the recyclability and recycling value of the material. In addition, the preparation process of this application adopts existing PET processing technologies such as melt polycondensation and twin-screw melt blending, which are fully compatible with existing production equipment, requiring no additional special equipment, and are easy to scale up. Furthermore, products with different performance orientations can be adapted to high-end fields such as flexible electronic device substrates, engineering plastic parts, and closed-loop recyclable packaging materials, breaking through the application limitations caused by the inherent brittleness of pure PET, realizing the high-end and functional upgrade of PET materials, and meeting the needs of green and low-carbon industrial development. Attached Figure Description

[0013] Figure 1 Infrared spectral comparison of pure PET, adaptive PET elastomer of Example 1 (sample A), and PET composite material of Example 2 (sample B) provided in the embodiments of this application; Figure 2 DMA storage modulus-temperature curves of pure PET, adaptive PET elastomer of Example 1 (sample A), and PET composite material of Example 2 (sample B) provided in the embodiments of this application. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0015] The core technical feature of this application is the introduction of quasi-rotaxane structures as sliding crosslinking points into the PET molecular network. A two-step end-capping-in-situ self-assembly process is employed to overcome the technical obstacles of PET chain end inertia and poor compatibility between polyrotaxane and PET. The "molecular pulley effect" of quasi-rotaxane is utilized to achieve high toughness in PET. Based on this, a soft-hard synergistic composite network is formed by combining rigid nanofillers modified with aminosilane coupling agents, achieving a synergistic improvement in toughness, strength, and modulus. Furthermore, by introducing dynamic covalent bonds, a dual-network structure of physical crosslinking of quasi-rotaxane and dynamic covalent chemical crosslinking is formed, endowing the material with thermomorphic properties and chemically closed-loop recyclability.

[0016] The technical solution of this application includes three types of core products, corresponding preparation methods, and industrial applications, as detailed below: This application provides an adaptive PET elastomer, which is prepared by in-situ self-assembly of end-functionalized PET through melt blending. The end-functionalized PET is a PET molecular chain with one end modified with a crown ether group and the other end modified with a primary amide group. A quasi-rotaxane supramolecular crosslinking network is integrated into the PET molecular network of the elastomer. The quasi-rotaxane structure is formed by the self-assembly of the crown ether group and the primary amide group of the end-functionalized PET through host-guest interactions. Furthermore, the quasi-rotaxane structure acts as a sliding crosslinking point, dissipating energy through the sliding motion of the cyclic components. The notched impact strength of the elastomer is ≥52.1 kJ / m. 2 After three melting and regranulation processes, the intrinsic viscosity retention rate is ≥85%.

[0017] Wherein, the crown ether group is benzo-24-crown-8 and / or dibenzo-24-crown-8; based on the total weight of the elastomer, the content of the component corresponding to the quasi-rotaxane structure is 0.5~10wt%, wherein when the content is 5wt%, the tensile strength of the elastomer is 55±3MPa, and when the content is 10wt%, the elongation at break of the elastomer is ≥520% and the notched impact strength is 60.5±5.5kJ / m. 2 .

[0018] This application also provides a method for preparing the above-mentioned adaptive PET elastomer, including the following steps: a) Hydroxyl-terminated PET prepolymer was prepared by melt polycondensation: using terephthalic acid and excess ethylene glycol as raw materials, antimony trioxide as catalyst, esterification was carried out at 250~260℃, followed by polycondensation at 270~280℃ and vacuum degree <100Pa to obtain a hydroxyl-terminated PET prepolymer with an intrinsic viscosity of 0.35dL / g. b) Preparation of terminal-functionalized PET via a two-step isocyanate / acyl chloride end-capping reaction: Hydroxyl-terminated PET prepolymer was reacted with p-toluenesulfonyl isocyanate in DMF at 80°C for 4 h to obtain terminal isocyanate PET, which was then reacted with an amino-modified crown ether at 60°C for 6 h to obtain PET with a crown ether group at one end; it was then reacted with excess adipic acid chloride in DMF to introduce acyl chloride end groups, and then reacted with excess 1,6-hexanediamine to obtain terminal-functionalized PET with a primary amide group at the other end; c) Melt blending in situ self-assembly: Dry end-functionalized PET is melt blended at 240~280℃ and 50~200rpm, and a quasi-rotaxane crosslinking network is formed through host-guest recognition of crown ether-amide to obtain adaptive PET elastomer.

[0019] Furthermore, this application embodiment also provides a PET composite material, which is prepared by melt blending the above-mentioned end-functionalized PET with rigid nanofillers modified by aminosilane coupling agent to form a soft-hard composite network in which a quasi-rotaxane supramolecular network and rigid nanofillers work together; the tensile strength of the composite material is ≥65MPa, the heat distortion temperature is ≥98℃, and the intrinsic viscosity retention rate after 3 melt regranulation is ≥88%.

[0020] The rigid nanofiller is at least one of graphene nanosheets and sepiolite mineral fibers, and the aminosilane coupling agent is 3-aminopropyltriethoxysilane; the content of the rigid nanofiller is 0.1~5wt% based on the total weight of the composite material.

[0021] Specifically, when graphene nanosheets and sepiolite mineral fibers are compounded at a mass ratio of 3:1 and the addition amount is 2wt%, the tensile strength of the composite material is 72±4MPa, the flexural modulus is 2.8±0.1GPa, and the heat distortion temperature is 102±3℃; when only 3wt% sepiolite mineral fibers are added, the notched impact strength of the composite material is 35.0±3.0kJ / m²; when 1.5wt% each of graphene nanosheets and sepiolite mineral fibers are added, the flexural modulus of the composite material is 2.7±0.1GPa.

[0022] This application embodiment also provides a method for preparing the above-mentioned PET composite material, including steps a) and b) above, and further comprising: d) Surface modification of rigid nanofillers: Rigid nanofillers were ultrasonically dispersed in ethanol, glacial acetic acid was added, the pH value was adjusted to 5.0, and then 1 wt% of aminosilane coupling agent relative to the total mass of the filler was added. The mixture was refluxed at 70°C for 6 h, and after centrifugation, washing and drying, the modified rigid nanofillers were obtained. e) Melt blending molding: The end-functionalized PET from step b) is premixed with the modified rigid nanofiller from step d), and then melt blended, extruded, and granulated at 240~280℃ and 50~200rpm to obtain the PET composite material.

[0023] Furthermore, this application also provides a PET-based dynamic covalent network polymer, which is obtained by melt molding of end-functionalized PET containing dynamic covalent bonds to form a dual network structure of quasi-rotaxane physical crosslinking and dynamic covalent chemical crosslinking; the dynamic covalent bonds are disulfide bonds or ester bonds that can undergo exchange reactions under the action of zincate catalysts; the polymer has a monomer recovery rate of >90% after catalytic depolymerization and a intrinsic viscosity retention rate of ≥95% after 3 melt regranulation.

[0024] Among them, the tensile strength of the polymer containing disulfide bonds can reach 60±3MPa, and the stress relaxation characteristic time at 180℃ is about 600s; the stress relaxation characteristic time of the polymer containing catalytically exchangeable ester bonds at 180℃ is about 120s, and the catalytic depolymerization monomer recovery rate is >92%.

[0025] This application also provides a method for preparing the above-mentioned PET-based dynamic covalent network polymer, including two preparation schemes: Option 1: Prepare a PET-based dynamic covalent network polymer containing disulfide bonds: a1) Preparation of hydroxyl-terminated PET prepolymer containing disulfide bonds: In the melt polycondensation stage of step a) above, dithiodibenzoic acid, accounting for 5% of the total molar amount of diacid, is introduced and co-condensed with terephthalic acid and ethylene glycol to obtain a hydroxyl-terminated PET prepolymer with disulfide bonds in the main chain. b1) Perform end-group functionalization according to the method in step b) above to obtain end-group functionalized PET containing disulfide bonds; c1) The polymer with a double network structure is obtained by melting and molding it at 240~280℃ and 50~200rpm; Option 2: Prepare a PET-based dynamic covalent network polymer containing catalytically exchangeable ester bonds: a2) Preparation of hydroxyl-terminated PET prepolymer containing secondary hydroxyl groups: Glycerol is added to provide secondary hydroxyl groups during the melt polycondensation stage of step a) above to obtain hydroxyl-terminated PET prepolymer containing secondary hydroxyl groups; b2) Perform end-group functionalization according to the method in step b) above to obtain end-group functionalized PET containing secondary hydroxyl groups; c2) It is mixed with 0.5wt% zincate catalyst and melt-molded at 240~280℃ and 50~200rpm to obtain a polymer with a dual network structure.

[0026] In Scheme 1, dithiodibenzoic acid is a dicarboxylic acid monomer containing a disulfide bond; in Scheme 2, glycerol is a secondary hydroxyl donor; and the zincate catalyst is a dedicated catalyst for transesterification reactions.

[0027] This application also provides an application of the above-mentioned adaptive PET elastomer, the above-mentioned PET composite material, and the above-mentioned PET-based dynamic covalent network polymer. The adaptive PET elastomer can be used to prepare flexible substrates for flexible electronic devices, bendable parts, etc.; the PET composite material can be used to prepare engineering plastic substrates, which can be molded and processed to obtain automotive parts, electronic and electrical housings, etc.; the PET-based dynamic covalent network polymer can be used to prepare closed-loop recyclable packaging materials, environmentally friendly engineering plastic parts, etc.

[0028] The following detailed embodiments illustrate the PET elastomers, composite materials, dynamic covalent network polymers, and their preparation methods provided in this application. Unless otherwise specified, the experimental methods used in the embodiments are conventional polymer material preparation processes; unless otherwise specified, the raw materials used are all industrial-grade pure products. Specifically, the graphene nanosheets are selected with a sheet thickness of 5-10 nm and a lateral dimension of 1-5 μm; the sepiolite is selected from needle-like mineral fibers with an aspect ratio of 200-300:1; heptadecafluorodecyltriethoxysilane and dithiodibenzoic acid are analytical grade; and the zincate catalyst is basic zinc carbonate zincate.

[0029] Example 1: Preparation of Adaptive PET Elastomer Synthesis of PET prepolymer: A conventional melt polycondensation method was used. Terephthalic acid (PTA): ethylene glycol (EG) was added at a molar ratio of 1:1.2. 166.13 g (1.0 mol) of PTA and 74.50 g (1.2 mol) of EG were added to a melt polycondensation reactor equipped with a stirring, condenser, and vacuum system. Antimony trioxide (0.03 wt% of PTA) was added as a catalyst. Nitrogen protection was first applied, and the temperature was raised to 250-260°C. Esterification was carried out at 0.1 MPa for 2.5 hours, until no condensate was observed in the separator, indicating completion of the esterification reaction. Subsequently, the nitrogen was turned off, and the vacuum was gradually increased to <100 Pa. The temperature was raised to 270-280°C for a polycondensation reaction for 2 hours, with continuous stirring (stirring speed 200 rpm) until the melt in the reactor reached the set viscosity. The reaction was then stopped, and the product was discharged, cooled, and granulated to obtain an intrinsic viscosity of 0.35. dL / g hydroxyl-terminated PET prepolymer.

[0030] Preparation of end-functionalized PET: (1) Crown ether end modification: 100g of the above-mentioned hydroxyl-terminated PET prepolymer was added to a three-necked flask, and N,N-dimethylformamide (DMF) was added to prepare a solution with a solid content of 25wt%. Stirring was started (350rpm) and the temperature was raised to 80℃. P-toluenesulfonyl isocyanate was added at a molar ratio of 1:1.08 for hydroxyl-terminated PET prepolymer and 1:1.08. The reaction was kept at a constant temperature for 4h to obtain a terminal isocyanate (-NCO) PET solution. The reaction system was then cooled to 60℃, and amino-modified benzo-24-crown-8 was added at a molar ratio of 1:1 for PET terminal isocyanate and benzo-24-crown-8 modified with amino. The reaction was continued at a constant temperature for 6h. After the reaction was completed, the product was poured into anhydrous ethanol to precipitate. After filtration, the filter cake was dried under vacuum at 80℃ for 12h to obtain a PET intermediate with a benzo-24-crown-8 crown ether group at one end.

[0031] (2) Amide end modification: Take 80g of the above crown ether modified PET intermediate and add it to a three-necked flask. Add DMF to prepare a solution with a solid content of 25wt%. Heat to 70℃ and stir (300rpm). Add excess adipic acid chloride according to the molar ratio of crown ether modified PET intermediate: adipic acid chloride = 1:1.15. React for 3h to introduce acyl chloride end groups. Then add excess 1,6-hexanediamine according to the molar ratio of acyl chloride end group PET: 1,6-hexanediamine = 1:1.15. Continue to react at a constant temperature for 3h. After the reaction is completed, pour the product into anhydrous ethanol to precipitate. After filtration, the filter cake is dried under vacuum at 80℃ for 12h to obtain crown ether-amide double-terminated PET with a primary amide group at the other end.

[0032] Quasi-rotaxane network molding: The above-mentioned dual-end functionalized PET was placed in a vacuum drying oven and dried at 120℃ and a vacuum degree of -0.095MPa or higher for 5 hours to remove moisture. The dried dual-end functionalized PET was added to a twin-screw extruder with an aspect ratio of L / D=40:1. The extruder temperatures were set as follows: feeding section 200~210℃, melting section 240~250℃, homogenization section 250~260℃, and die head 250℃. The screw speed was 100 rpm. Under the action of shear force and temperature, the crown ether groups and primary amide groups underwent host-guest recognition and in-situ self-assembly to form a quasi-rotaxane supramolecular crosslinking network. After the melt was extruded through the die head, it was cooled by a cold water bath at 25~30℃ and then pelletized by a pelletizer (pelletizing speed 350 rpm) to obtain the finished product of quasi-rotaxane-based adaptive PET elastomer, in which the content of the component corresponding to the quasi-rotaxane structure was 0.5wt%.

[0033] Example 1a: Adaptive PET elastomer with 5wt% quasi-rotaxane network component The preparation method was completely consistent with Example 1, except that the amount of double-ended functionalized PET added was adjusted in the quasi-rotaxane network molding step, so that the proportion of double-ended functionalized PET in the total material was 5 wt%, and the remainder was unfunctionalized pure PET prepolymer. After melt blending and self-assembly, an adaptive PET elastomer with a quasi-rotaxane network component content of 5 wt% was obtained. The notched impact strength of this sample was 52.1 ± 5.0 kJ / m. 2 Tensile strength 55±3MPa.

[0034] Example 1b: Adaptive PET elastomer with 10 wt% quasi-rotaxane network component The preparation method is completely consistent with Example 1, except that the amount of double-ended functionalized PET added is adjusted in the quasi-rotaxane network molding step, so that the proportion of double-ended functionalized PET in the total material is 10 wt%, and the remainder is unfunctionalized pure PET prepolymer. After melt blending and self-assembly, an adaptive PET elastomer with a quasi-rotaxane network component content of 10 wt% is obtained. The notched impact strength of this sample is 60.5 ± 5.5 kJ / m. 2 Elongation at break: 520±60%.

[0035] Example 2: Preparation of Quasi-Rotaxane / Rigid Nanofiller PET Composite Material Pretreatment of fluorinated nano-hybrid filler: 10g of mixed filler was taken at a mass ratio of graphene nanosheets (GNP): sepiolite = 3:1, and 500mL of anhydrous ethanol was added. The mixture was placed in an ultrasonic disperser and ultrasonically dispersed at 400W for 1.5h to obtain a uniform filler dispersion. The dispersion was transferred to a three-necked flask, glacial acetic acid was added, and the pH was adjusted to 5.0. Then, 0.1g of heptadecafluorodecyltriethoxysilane (1 wt% relative to the total mass of the filler) was added. The mixture was heated to 70℃ and refluxed with stirring at 250rpm for 6h. After the reaction, the mixture was placed in a high-speed centrifuge and centrifuged at 9000rpm for 10min. The supernatant was discarded, and the lower solid was washed three times with anhydrous ethanol. Then, it was dried in a vacuum drying oven at 80℃ for 12h to obtain surface-fluorinated modified GNP / sepiolite nano-hybrid filler.

[0036] Preparation of composite material: 98g of the double-ended functionalized PET obtained in Example 1 and 2g of the above modified nano-hybrid filler were added to a high-speed mixer and premixed at 1200rpm for 8min to obtain a uniform mixture. The mixture was added to a twin-screw extruder with an aspect ratio of L / D=40:1. The extruder temperatures were set as follows: feeding section 210~220℃, melting section 245~255℃, homogenization section 255~265℃, and die head 260℃. The screw speed was 150rpm. After melt blending, the mixture was extruded. The melt was cooled by a 25~30℃ cold water bath and pelletized by a pelletizer (350rpm) to obtain a quasi-rotaxane / rigid nano-filler PET composite material containing 2wt% fluorinated nano-hybrid filler. The sample had a tensile strength of 72±4MPa and a heat distortion temperature of 102±3℃.

[0037] Example 2a Quasi-rotaxane / nanofiller PET composite material containing 3 wt% modified sepiolite The preparation method was basically the same as in Example 2, except that the type and amount of filler were adjusted: graphene nanosheets were removed, and only sepiolite modified with heptadecafluorodecyltriethoxysilane was used as filler. The filler addition amount was 3 wt% relative to the total material (i.e., 97 g of double-ended functionalized PET and 3 g of modified sepiolite). The remaining premixing and melt blending process parameters were completely consistent with those in Example 2, and a PET composite material containing 3 wt% modified sepiolite was obtained. The notched impact strength of this sample was 35.0 ± 3.0 kJ / m. 2 Flexural modulus 2.5±0.1GPa.

[0038] Example 2b: Quasi-rotaxane / nanofiller PET composite material containing 1.5wt% GNP + 1.5wt% sepiolite The preparation method is basically the same as in Example 2, except that the filler ratio and addition amount are adjusted: graphene nanosheets and sepiolite are modified separately by heptadecafluorodecyltriethoxysilane and then physically mixed at a mass ratio of 1:1. The total amount of filler added is 3wt% relative to the total material (i.e., 97g of double-ended functionalized PET, 1.5g of modified GNP, and 1.5g of modified sepiolite). The remaining premixing and melt blending process parameters are completely consistent with those in Example 2. The PET composite material is obtained with a flexural modulus of 2.7±0.1GPa and a heat distortion temperature of 100±3℃.

[0039] Figure 1 The infrared spectra of pure PET raw material and quasi-rotaxane modified PET (Example 1: Adaptive PET elastomer (sample A) and Example 2: PET composite material (sample B)) are compared; the horizontal axis represents wavenumber (cm²). -1 The vertical axis represents absorbance; the characteristic peak of the COC bond in pure PET is at 10¹⁸ cm⁻¹. -1 The characteristic peak of quasi-rotaxane-modified PET occurs at approximately 4 cm⁻¹.-1 The blue shift confirms that a host-guest interaction occurs between the crown ether and the amide, leading to the self-assembly of quasi-rotaxanes.

[0040] Figure 2 The DMA storage modulus-temperature curves are shown for pure PET, the adaptive PET elastomer of Example 1 (sample A), and the PET composite material of Example 2 (sample B). The horizontal axis represents temperature (°C), and the vertical axis represents storage modulus (MPa). The quasi-rotaxane PET elastomer exhibits a significant rubber plateau in the region above the glass transition temperature of PET, confirming the existence of the quasi-rotaxane dynamic crosslinking network. The storage modulus of the quasi-rotaxane / nanofiller PET composite material is higher than that of pure PET throughout the curve, confirming the effective enhancement of modulus by the nanofiller.

[0041] Example 3 Quasi-rotaxane-enhanced closed-loop recyclable PET Vitrimer (disulfide bond type) Synthesis of hydroxyl-terminated PET prepolymer containing disulfide bonds: The diacids were fed in a molar ratio of 1:1.2 (total molar amount of diacids: EG), with a molar ratio of 95:5 for terephthalic acid: dithiobenzoic acid. 157.82 g (0.95 mol) of PTA, 13.71 g (0.05 mol) of dithiobenzoic acid, and 74.50 g (1.2 mol) of EG were added to a melt polycondensation reactor. Antimony trioxide (0.03 wt% of the total diacid mass) was added as a catalyst. Subsequent esterification (250-260℃, 2.5 h) and polycondensation (270-280℃, <100 Pa, 2 h) process parameters were identical to those in Example 1. After the reaction, the material was discharged, cooled, and granulated to obtain a hydroxyl-terminated PET prepolymer with dynamic disulfide bonds in the main chain, exhibiting an intrinsic viscosity of 0.35 dL / g.

[0042] End-group functionalization and dual-network molding: The above-mentioned PET prepolymer containing disulfide bonds was subjected to crown ether-amide dual-end functionalization. The process parameters such as raw material ratio, reaction temperature, time, and solvent dosage were completely consistent with those in Example 1, resulting in dual-end functionalized PET containing disulfide bonds. Subsequently, the functionalized PET was dried at 120°C under vacuum for 5 hours and then fed into a twin-screw extruder. It was melt-molded according to the extrusion process parameters of the example (250~260°C, 100 rpm). During the processing, the melt simultaneously formed a quasi-rotaxane physical crosslinking network and a disulfide bond chemical crosslinking network, finally obtaining a quasi-rotaxane-reinforced disulfide bond type PET-based dynamic covalent network polymer (PET Vitrimer). The monomer recovery rate of this sample after catalytic depolymerization was >90%, and the intrinsic viscosity retention rate after 3 melt regranulation was ~95%.

[0043] Example 3a Quasi-rotaxane-enhanced closed-loop PET recovery Vitrimer (catalytic transesterification system) Synthesis of hydroxyl-terminated PET prepolymer containing secondary hydroxyl groups: PTA and EG were fed in a melt polycondensation reactor at a ratio of 1:1.2 mol as described in Example 1. 166.13 g of PTA and 74.50 g of EG were added, along with 1.5% of EG molars of glycerol as a secondary hydroxyl donor and 0.03 wt% of PTA as a catalyst. The subsequent esterification and polycondensation process parameters were completely consistent with those in Example 1, resulting in a hydroxyl-terminated PET prepolymer with secondary hydroxyl groups in the main chain and an intrinsic viscosity of 0.35 dL / g.

[0044] End-group functionalization and catalytic transesterification network formation: The above-mentioned PET prepolymer containing secondary hydroxyl groups was subjected to crown ether-amide dual-end functionalization, with process parameters completely consistent with Example 1, to obtain dual-end functionalized PET containing secondary hydroxyl groups; the functionalized PET was dried at 120°C under vacuum for 5 hours, and then thoroughly mixed with 0.5 wt% of zincate catalyst (basic zinc carbonate zincate) relative to the total material, and added to a twin-screw extruder. It was melt-blended and formed according to the extrusion process parameters of Example 1 (250~260°C, 100 rpm). Under the action of zincate catalyst, the melt formed a dual network structure of quasi-rotaxane physical crosslinking and transesterification chemical crosslinking, to obtain catalytic transesterification type PET Vitrimer. The stress relaxation characteristic time of this sample at 180°C was ~120s, and the catalytic depolymerization monomer recovery rate was >92%.

[0045] Comparative Example 1: Direct blending of polyrotaxane with PET (Prior Art) Synthesis of model polyrotaxane: Model polyrotaxane was synthesized using polyethylene glycol (PEG, molecular weight 2000) as the axis and α-cyclodextrin as the ring. PEG and α-cyclodextrin were added to deionized water at a molar ratio of 1:10 and stirred at 80°C for 6 hours. After centrifugation, washing and drying, the uncapped polyrotaxane intermediate was obtained.

[0046] Direct melt blending: 95g of pure PET prepolymer (intrinsic viscosity 0.35 dL / g) and 5g of the above-mentioned model polyrotaxane were added to a high-speed mixer and premixed at 1000 rpm for 5 min. The mixture was then added to a twin-screw extruder, and the extrusion temperature was set to 270℃ and the screw speed to 100 rpm. After melt blending, the mixture was extruded and granulated to obtain a polyrotaxane-modified PET sample. The notched impact strength of this sample was 8.2 ± 0.8 kJ / m. 2 Tensile strength 41±2MPa.

[0047] Comparative Example 2: Toughened PET with Traditional Elastomers (Prior Art) Take 85g of pure PET prepolymer (intrinsic viscosity 0.35 dL / g) and 15g of commercially available core-shell acrylate toughening agent, add them to a high-speed mixer, and premix at 1200 rpm for 8 minutes. Add the mixture to a twin-screw extruder, set the extrusion temperature to 260~270℃ and the screw speed to 100 rpm, and after melt blending, extrude and granulate to obtain a traditional elastomer-toughened PET sample. The notched impact strength of this sample is 8.0±1.0 kJ / m. 2 Flexural modulus 1.5±0.1GPa.

[0048] Mechanical properties, thermal properties, and recyclability were tested on the above embodiments, comparative examples, and pure PET samples. The test methods all followed national / industry standards. Tensile strength was tested according to GB / T 1040.2, notched impact strength according to GB / T1843 (simply supported beam A-type notch), heat distortion temperature according to GB / T 1634.2 (1.82MPa), and intrinsic viscosity according to GB / T14190. The specific test results are shown in Tables 1 and 2.

[0049] Table 1. Test results of mechanical and thermal properties of each sample Table 2 Results of Recyclability and Dynamic Performance Tests for Each Sample In summary, as shown in Tables 1 and 2, the adaptive PET elastomer of this application has excellent toughness, the PET composite material achieves synergistic improvement in toughness, strength, and modulus, and the PET-based dynamic covalent network polymer has both high toughness and closed-loop recyclability. The comprehensive performance of the three types of products is far superior to that of pure PET and traditional modified PET, thus solving the technical contradiction of toughening traditional PET.

[0050] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An adaptive PET elastomer, characterized in that, The adaptive PET elastomer is prepared by in-situ self-assembly of end-functionalized PET through melt blending. The end-functionalized PET is a PET molecular chain with a crown ether group modified at one end and a primary amide group modified at the other end. The PET molecular network of the adaptive PET elastomer integrates a quasi-rotaxane supramolecular crosslinking network. The quasi-rotaxane structure in this network is formed by the self-assembly of the crown ether group and the primary amide group of the end-functionalized PET through host-guest interaction. The quasi-rotaxane structure acts as a sliding crosslinking point and can dissipate energy through the sliding motion of the cyclic components.

2. The adaptive PET elastomer according to claim 1, characterized in that, The crown ether group is benzo-24-crown-8 and / or dibenzo-24-crown-8; the content of the end-functionalized PET component forming the quasi-rotaxane structure is 0.5-10 wt% based on the total weight of the adaptive PET elastomer.

3. A method for preparing the adaptive PET elastomer as described in claim 1 or claim 2, characterized in that, include: a) Hydroxyl-terminated PET prepolymer was prepared by melt polycondensation; b) By introducing crown ether groups and amide groups into both ends of PET prepolymer through a two-step isocyanate / acyl chloride end-capping reaction, terminal functionalized PET is obtained; c) The end-functionalized PET is melt-blended at 240-280°C and 50-200 rpm, and a quasi-rotaxane crosslinking network is formed through host-guest recognition of crown ether-amide to obtain an adaptive PET elastomer.

4. The method for preparing the adaptive PET elastomer according to claim 3, characterized in that, Step b) includes: Hydroxyl-terminated PET prepolymer was reacted with p-toluenesulfonyl isocyanate in DMF at 80°C for 4 h to obtain isocyanate-terminated PET, which was then reacted with amino-modified benzo-24-crown-8 and / or dibenzo-24-crown-8 at 60°C for 6 h to obtain PET with a crown ether group at one end. PET with a crown ether group at one end is reacted with excess adipic acid chloride in DMF to introduce an acyl chloride end group, and then reacted with excess 1,6-hexanediamine to obtain a terminal functionalized PET with a primary amide group at the other end.

5. A PET composite material, characterized in that, The PET composite material is prepared by melt blending the end-functionalized PET as described in claim 1 with rigid nanofillers that have been surface modified with an aminosilane coupling agent, forming a soft-hard composite network in which a quasi-rotaxane supramolecular network and rigid nanofillers work synergistically.

6. The PET composite material according to claim 5, characterized in that, The rigid nanofiller is at least one of graphene nanosheets and sepiolite mineral fibers; the aminosilane coupling agent is heptadecafluorodecyltriethoxysilane.

7. A method for preparing the PET composite material as described in claim 5 or claim 6, characterized in that, Including steps a) and b) as described in claim 3, it further includes: d) Surface modification of rigid nanofillers: Rigid nanofillers were ultrasonically dispersed in ethanol, glacial acetic acid was added, the pH value was adjusted to 5.0, and then 1 wt% of aminosilane coupling agent relative to the total mass of the filler was added. The mixture was refluxed at 70°C for 6 h, and after centrifugation, washing and drying, the modified rigid nanofillers were obtained. e) Melt blending molding: The end-functionalized PET from step b) is premixed with the modified rigid nanofiller from step d), and then melt-blended and extruded in a twin-screw extruder at 240-280℃ and 50-200rpm to obtain a PET composite material.

8. A PET-based dynamic covalent network polymer, characterized in that, It is prepared by melt molding of end-functionalized PET containing dynamic covalent bonds, forming a dual network structure of quasi-rotaxane physical crosslinking and dynamic covalent chemical crosslinking; the dynamic covalent bonds are disulfide bonds or ester bonds that can catalyze transesterification.

9. A method for preparing the PET-based dynamic covalent network polymer as described in claim 8, characterized in that, include: Option 1: Prepare a polymer containing disulfide bonds: a1) Preparation of hydroxyl-terminated PET prepolymer containing disulfide bonds: In the melt polycondensation stage of step a) of claim 3, dithiodibenzoic acid, accounting for 5% of the total molar amount of diacid, is introduced and co-condensed with terephthalic acid and ethylene glycol to obtain a hydroxyl-terminated PET prepolymer with disulfide bonds in the main chain. b1) The disulfide-bonded hydroxyl-terminated PET prepolymer is end-functionalized according to the method of step b) of claim 3 to obtain disulfide-bonded end-functionalized PET. c3) The end-functionalized PET containing disulfide bonds is melt-molded at 240-280℃ and 50-200rpm to obtain a polymer with a dual network structure; Alternatively, in option two, a polymer containing catalytically exchangeable ester bonds can be prepared: a2) Preparation of hydroxyl-terminated PET prepolymer containing secondary hydroxyl groups: Glycerol is added to provide secondary hydroxyl groups during the melt polycondensation stage of step a) in claim 3 to obtain hydroxyl-terminated PET prepolymer containing secondary hydroxyl groups; b2) Perform end-group functionalization according to the method in step b) of claim 3 to obtain end-group functionalized PET containing secondary hydroxyl groups; c2) The terminal functionalized PET containing secondary hydroxyl groups is mixed with 0.5 wt% zincate catalyst and melt-molded at 240-280℃ and 50-200 rpm to obtain a polymer with a dual network structure.

10. The use of the adaptive PET elastomer of claim 1, the PET composite material of claim 5, and the PET-based dynamic covalent network polymer of claim 8 in the preparation of flexible electronic devices, engineering plastics, or recyclable packaging materials.

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