A modified PET composite material based on reactive interface toughening, its preparation method and application

Abstract

This invention provides a modified PET composite material based on reactive interface toughening, its preparation method, and its application, belonging to the field of polymer materials technology. The modified PET composite material provided by this invention comprises PET resin, a reactive interface toughening agent, nano-reinforcing fillers, a crosslinking agent, a core-shell toughening agent, a crystallization promoter, and processing aids. By constructing a multi-level synergistic structure of "rigid crosslinked network – chemically bonded flexible interface – core-shell toughening unit," this invention enables the PET material to maintain high strength, high modulus, and high heat resistance while achieving a several-fold increase in notched impact strength. This achieves a simultaneous and significant improvement in the strength, toughness, and heat resistance of the PET material, reaching a "rigid-toughness balance," making it suitable for engineering fields with stringent comprehensive performance requirements.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a modified PET composite material based on reactive interface toughening, its preparation method, and its application. Background Technology

[0002] Polyethylene terephthalate (PET) is widely used in the field of engineering plastics due to its excellent mechanical properties, chemical resistance, electrical insulation, and low cost. However, pure PET has inherent disadvantages such as slow crystallization rate, poor notched impact toughness, and sensitivity to notches, which limit its application in fields with stringent requirements for comprehensive material performance, such as automotive, electronics, and high-end structural components.

[0003] Currently, existing technologies for modifying PET mainly focus on simple blending reinforcement or toughening. For example, patent CN104151577A discloses the use of nano-silica and magnesium borate whiskers to reinforce PET, which improves strength and heat resistance, but has limited improvement on toughness. CN112322001A uses EPDM rubber and metal-organic framework materials for toughening, which improves impact strength, but often sacrifices the material's rigidity, heat resistance, and dimensional stability. CN112646333A uses PET / PA66 blends and PP-g-MAH compatibilizers to balance performance, but the compatibility control of this system is complex, and its long-term resistance to damp heat aging faces challenges.

[0004] Therefore, the technical shortcomings of existing modified PET materials are: it is difficult to maintain or even improve the rigidity, strength and heat resistance of PET while significantly improving its toughness and impact resistance (i.e., to achieve a "rigid-toughness balance"), and to ensure the performance stability of the modified system under long-term use and the feasibility of industrial production. Summary of the Invention

[0005] The purpose of this invention is to provide a modified PET composite material based on reactive interface toughening, its preparation method and application, wherein the modified PET composite material has excellent comprehensive mechanical properties, heat resistance and impact resistance.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a modified PET composite material based on reactive interface toughening, comprising the following raw materials in parts by weight: 100 parts PET resin; 5-15 parts reactive interface toughening agent; 1-5 parts nano-reinforcing filler; 0.5-3.0 parts crosslinking agent; 3-12 parts core-shell toughening agent; 0.3-2.0 parts crystallization promoter; 0.5-2.0 parts processing aid; The reactive interface toughening agent contains epoxy groups; The nano-reinforced filler is an amino-modified reinforced filler.

[0007] Preferably, the reactive interface toughening agent is an ethylene-acrylate copolymer containing epoxy functional groups.

[0008] Preferably, the nano-reinforced filler is aminosilane coupling agent modified nano-silica.

[0009] Preferably, the crosslinking agent is dicyclopentadiene diesteroxide.

[0010] Preferably, the core-shell toughening agent is an acrylate core-shell copolymer.

[0011] Preferably, the crystallization promoter is an organophosphate nucleating agent or nano-hydroxyapatite.

[0012] Preferably, the processing aids include antioxidants and lubricants.

[0013] This invention provides a method for preparing the modified PET composite material described above, comprising the following steps: A reactive interface toughening agent, nano-reinforcing filler, partial crosslinking agent and crystallization accelerator are mixed. The resulting mixture is then melt-blended with PET resin and extruded and granulated to obtain a pre-grafted reinforced toughening masterbatch. The pre-grafted reinforced and toughened masterbatch is mixed with the core-shell toughening agent, the remaining crosslinking agent and processing aids, and then subjected to a second melt blending, followed by extrusion granulation and injection molding to obtain the modified PET composite material.

[0014] Preferably, the temperature of the first melt blend is 230~260°C and the screw speed is 200~400 rpm; the temperature of the second melt blend is 240~270°C and the screw speed is 250~350 rpm; the barrel temperature of the injection molding is 240~280°C and the mold temperature is 120~140°C.

[0015] This invention provides applications of the modified PET composite material described in the above technical solution or the modified PET composite material prepared by the preparation method described in the above technical solution in the fields of automotive parts, electronic and electrical components or high-end structural parts.

[0016] This invention provides a modified PET composite material based on reactive interface toughening. By constructing a multi-level synergistic structure of "rigid cross-linked network - chemically bonded flexible interface - core-shell toughening unit", the PET material maintains high strength, high modulus and high heat resistance while its notched impact strength is increased several times. This achieves a simultaneous and significant improvement in the strength, toughness and heat resistance of the PET material, reaching a "rigid-toughness balance", and is suitable for engineering fields with demanding comprehensive performance requirements.

[0017] Mechanism and beneficial effects of the present invention: 1. Multi-level synergistic structure design: This invention constructs a three-level synergistic structure within a PET matrix. The first level involves a sparse cross-linked network formed by the reaction of a cross-linking agent with PET end groups, providing excellent rigidity, heat resistance, and dimensional stability. The second level utilizes the epoxy groups of a reactive interfacial toughening agent, which simultaneously react with the end groups of PET and the amino groups of the nano-reinforcing filler (aminated SiO2), constructing an interfacial layer between the rigid filler and the resin matrix that is firmly anchored by chemical bonds and rich in flexible segments (E-MA). This interfacial layer effectively transfers stress and absorbs and dissipates a large amount of energy under high stress through large deformation and slippage of the segments, achieving a "rigidity-toughness balance." The third level consists of dispersed core-shell toughening agents, which act as stress concentration points, further preventing crack propagation through the deformation of their soft core.

[0018] 2. Excellent comprehensive performance: Through the synergistic effect of the above-mentioned multi-level structure, the prepared PET composite material maintains high tensile strength (≥130 MPa), high flexural modulus (≥5.5 GPa), and high heat distortion temperature (≥110°C), while also exhibiting high notched impact strength (≥20 kJ / m²). 2 The performance has been improved several times over, completely overcoming the contradiction of traditional PET or simple reinforced / toughened modified materials being "strong but not tough" or "tough but not heat resistant".

[0019] 3. Excellent interfacial stability and durability: Since the nano-reinforced filler is connected to the matrix by strong chemical bonds (CN, CO bonds) rather than traditional physical adsorption or weak van der Waals forces, the long-term stability, resistance to damp heat aging and fatigue resistance of the interface are significantly enhanced, solving the industry problem of easy agglomeration of nano-fillers and easy interface failure.

[0020] 4. High industrial feasibility: The main raw materials used in this invention (E-MA-GMA, nano SiO2, common crosslinking agents and toughening agents) are all commercial products with wide availability and controllable costs.

[0021] This invention first constructs a chemically bonded, flexible, and stable interface between the nano-reinforced filler and the PET matrix through a melt reaction; subsequently, a core-shell toughening agent is introduced for final mixing. The method of this invention uses readily available raw materials, has a clear process flow, and is stable. It is easily controlled and scaled up in existing twin-screw extrusion production lines, making it suitable for industrial production. Detailed Implementation

[0022] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0023] This invention provides a modified PET composite material based on reactive interface toughening, comprising the following raw materials in parts by weight: 100 parts PET resin; 5-15 parts reactive interface toughening agent; 1-5 parts nano-reinforcing filler; 0.5-3.0 parts crosslinking agent; 3-12 parts core-shell toughening agent; 0.3-2.0 parts crystallization promoter; 0.5-2.0 parts processing aid; The reactive interface toughening agent contains epoxy groups; The nano-reinforced filler is an amino-modified reinforced filler.

[0024] The raw materials for preparing the modified PET composite material provided by this invention, by weight, include 100 parts of PET resin. This invention does not impose any specific limitation on the PET resin; any commercially available product well-known in the art is acceptable.

[0025] Based on the mass fraction of the PET resin, the raw materials for preparing the modified PET composite material provided by the present invention include 5 to 15 parts of reactive interface toughening agent, preferably 6 to 12 parts, and more preferably 8 to 10 parts.

[0026] In this invention, the reactive interface toughening agent is preferably an ethylene-acrylate copolymer containing epoxy functional groups, more preferably an ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) terpolymer, wherein the epoxy functional group content is 1~8 wt%.

[0027] Based on the mass fraction of the PET resin, the raw materials for preparing the modified PET composite material provided by the present invention include 1 to 5 parts of nano-reinforcing filler, preferably 2 to 4 parts, and more preferably 3 parts.

[0028] In this invention, the nano-reinforced filler is preferably aminosilane coupling agent modified nano-silica, and the average particle size of the nano-reinforced filler is preferably 10-50 nm, more preferably 20-30 nm. The aminosilane coupling agent preferably includes γ-aminopropyltriethoxysilane (KH550).

[0029] In this invention, the preferred method for preparing the aminosilane coupling agent modified nano-silica is as follows: Nano-silica was placed in a vacuum oven and dried at 110~120℃ for 4~6 hours (the purpose of which is to remove the surface adsorbed moisture and improve the surface hydroxyl activity), and then cooled to room temperature to obtain activated nano-silica. Prepare an ethanol-water mixed solvent by mixing anhydrous ethanol and deionized water in a mass ratio of 95:5. Add an aminosilane coupling agent to make its mass concentration 2-5%. Adjust the pH to 4.0-5.0 with glacial acetic acid. Stir magnetically at 25-30℃ for 30-60 minutes to hydrolyze the aminosilane coupling agent and obtain a clear hydrolysate. Activated nano-silica was added to the above hydrolysate at a solid-liquid ratio of 1:10 to 1:20 (g / mL), and ultrasonically dispersed (power 300-500W, frequency 40kHz) for 15-30 min. The resulting dispersion was transferred to a three-necked flask equipped with a reflux condenser and mechanically stirred in a water bath at 70-80℃ for 3-5 h at a stirring speed of 300-500 rpm. After the reaction was completed, the suspension was centrifuged at 8000-10000 rpm for 10-15 min, the precipitate was collected, and the precipitate was washed 3-5 times with anhydrous ethanol. The obtained product was placed in a vacuum oven and vacuum dried at 60-80℃ for 12-24 h. The dried lumps were ground in a mortar and pestle to obtain aminosilane coupling agent modified nano-silica.

[0030] Based on the mass fraction of the PET resin, the raw materials for preparing the modified PET composite material provided by the present invention include 0.5 to 3.0 parts of crosslinking agent, preferably 1.0 to 2.0 parts, and more preferably 1.5 parts.

[0031] In this invention, the crosslinking agent is preferably dicyclopentadiene diepoxide (CAS: 81-21-0).

[0032] Based on the mass fraction of the PET resin, the raw materials for preparing the modified PET composite material provided by the present invention include 3 to 12 parts of core-shell toughening agent, preferably 5 to 10 parts, and more preferably 6 to 8 parts.

[0033] In this invention, the core-shell toughening agent is preferably an acrylate core-shell copolymer, with the core being butyl acrylate crosslinked rubber and the shell being PMMA, derived from Dow Chemical's Paraaloid™ EXL-2330.

[0034] Based on the mass fraction of the PET resin, the raw materials for preparing the modified PET composite material provided by the present invention include 0.3 to 2.0 parts of crystallization promoter, preferably 0.5 to 1.8 parts, more preferably 0.8 to 1.5 parts, and even more preferably 1.0 to 1.2 parts.

[0035] In this invention, the crystallization promoter is preferably an organophosphate nucleating agent or nano-hydroxyapatite; the organophosphate nucleating agent is preferably sodium phenylphosphinate.

[0036] Based on the mass fraction of the PET resin, the raw materials for preparing the modified PET composite material provided by the present invention include 0.5 to 2.0 parts of processing aid, preferably 0.6 to 1.8 parts, more preferably 0.8 to 1.5 parts, and even more preferably 1.0 to 1.2 parts.

[0037] In this invention, the processing aid preferably includes antioxidants and lubricants; the antioxidant is preferably a mixture of hindered phenolic antioxidants (preferably antioxidant 1010) and phosphite antioxidants (preferably antioxidant 168); this invention does not have a special limitation on the mass ratio of the hindered phenolic antioxidant to the phosphite antioxidant, which can be adjusted according to needs, and is more preferably 1:2.

[0038] In this invention, the lubricant is preferably pentaerythritol stearate or ethylene bis-stearamide.

[0039] The present invention does not impose any special limitation on the mass ratio of the antioxidant and the lubricant, which can be adjusted according to the needs, and is more preferably 1:1.

[0040] This invention provides a method for preparing the modified PET composite material described above, comprising the following steps: A reactive interface toughening agent, nano-reinforcing filler, partial crosslinking agent and crystallization accelerator are mixed. The resulting mixture is then melt-blended with PET resin and extruded and granulated to obtain a pre-grafted reinforced toughening masterbatch. The pre-grafted reinforced and toughened masterbatch is mixed with the core-shell toughening agent, the remaining crosslinking agent and processing aids, and then subjected to a second melt blending, followed by extrusion granulation and injection molding to obtain the modified PET composite material.

[0041] In this invention, the PET resin and nano-reinforced filler are first vacuum dried at 120~140°C (more preferably 125~130°C) for 4~8 hours (more preferably 5~6 hours) to reduce the moisture content to less than 50 ppm before being mixed.

[0042] In this invention, all reactive interface toughening agents, all nano-reinforcing fillers, 30-70% (more preferably 50-60%) of crosslinking agents, and all crystallization accelerators are mixed in a high-speed mixer at room temperature for 3-10 minutes (more preferably 5-8 minutes) to obtain a first premix. The first premix and all PET resin are metered and fed into the main feed port and side feed port of a twin-screw extruder, respectively, and subjected to a first melt blending at 230-260°C (more preferably 245-250°C) and a screw speed of 200-400 rpm (more preferably 300-350 rpm), followed by extrusion granulation to obtain a pre-grafted reinforced toughening masterbatch. The length-to-diameter ratio (L / D) of the twin-screw extruder is preferably ≥40.

[0043] The pre-grafted reinforced and toughened masterbatch, core-shell toughening agent, remaining crosslinking agent, and processing aids are mixed evenly in a high-speed mixer to obtain a second premix. The second premix is ​​fed into another twin-screw extruder and subjected to a second melt blending, extrusion, water cooling, pelletizing, and drying at 240~270°C (more preferably 250~260°C) and a screw speed of 250~350 rpm (more preferably 300 rpm) to obtain pellets. The obtained granules are dried at 120~140°C (more preferably 125~130°C) and then injection molded in an injection molding machine at a barrel temperature of 240~280°C (more preferably 250~260°C) and a mold temperature of 120~140°C (more preferably 125~130°C) to obtain a modified PET composite material.

[0044] This invention provides applications of the modified PET composite material described in the above technical solution or the modified PET composite material prepared by the preparation method described in the above technical solution in the fields of automotive parts, electronic and electrical components or high-end structural parts.

[0045] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0046] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the raw materials used are all commercially available products, and the proportions are all by mass percentage.

[0047] In the following examples, the preparation method of KH550 modified nano-silica is as follows: Nano-silica was placed in a vacuum oven and dried at 120°C for 5 hours, then cooled to room temperature to obtain activated nano-silica. Prepare an ethanol-water mixed solvent with anhydrous ethanol:deionized water in a mass ratio of 95:5, add an aminosilane coupling agent to make its mass concentration 5%, adjust the pH to 5.0 with glacial acetic acid, and stir magnetically at 25°C for 50 min to obtain a clear hydrolysate. Activated nano-silica was added to the above hydrolysate at a solid-liquid ratio of 1:15 (g / mL), and ultrasonically dispersed (power 400W, frequency 40kHz) for 20 min. The resulting dispersion was transferred to a three-necked flask equipped with a reflux condenser and mechanically stirred in an 80℃ water bath for 5 h at a stirring speed of 500 rpm. After the reaction was completed, the suspension was centrifuged at 10000 rpm for 15 min, the precipitate was collected, and the precipitate was washed 5 times with anhydrous ethanol. The obtained product was placed in a vacuum oven and vacuum dried at 680℃ for 24 h. The dried block was ground with a mortar and pestle to obtain KH550 surface-treated nano-silica.

[0048] Examples 1-3 and Comparative Examples 1-3

[0049] Table 1. Formulations (parts by weight) of Examples 1-3 and Comparative Examples 1-3

[0050] Weigh each ingredient according to the formula in Table 1: PET resin: chips with a viscosity of 0.85 dL / g.

[0051] Reactive interface toughening agent: E-MA-GMA (DuPont, Elvaloy® PTW, epoxy value 3%).

[0052] Nano-reinforced filler: KH550 modified nano-silica (average particle size 20 nm).

[0053] Crosslinking agent: Dicyclopentadiene diepoxide.

[0054] Core-shell toughening agent: acrylate core-shell copolymer, with butyl acrylate crosslinked rubber as the core and PMMA as the shell, derived from Dow Chemical's Paraaloid™ EXL-2330.

[0055] Crystallization promoter: Sodium phenylphosphinate.

[0056] Antioxidant: 1010 / 168 = 1 / 2 (mass ratio).

[0057] Lubricant: Pentaerythritol stearate.

[0058] Preparation steps: Weigh according to the formula, and first vacuum dry the PET resin and nano-reinforced filler at 130°C for 8 hours to make the moisture content less than 50 ppm; All reactive interface toughening agents, all nano-reinforcing fillers, 50% of the total crosslinking agent, and all crystallization accelerators were mixed in a high-speed mixer at room temperature for 5 minutes to obtain a first premix. The first premix and all PET resin were metered and fed into the main feed port and side feed port of a twin-screw extruder, respectively, and subjected to first melt blending at 245°C and a screw speed of 300 rpm. The mixture was then extruded and granulated to obtain a pre-grafted reinforced and toughened masterbatch. The length-to-diameter ratio of the twin-screw extruder was L / D = 40.

[0059] The pre-grafted reinforced toughening masterbatch, core-shell toughening agent, remaining crosslinking agent, and processing aids are mixed evenly in a high-speed mixer to obtain a second premix. The second premix is ​​fed into another twin-screw extruder and subjected to a second melt blending, extrusion, water cooling, pelletizing, and drying at 260°C and a screw speed of 300 rpm to obtain pellets. After drying the obtained granules at 120°C, they were injection molded in an injection molding machine at a barrel temperature of 250°C and a mold temperature of 130°C to obtain a modified PET composite material.

[0060] Comparative Example 1

[0061] Pure PET: Contains no reactive interface toughening agents, nano-reinforcing fillers, crosslinking agents, or core-shell toughening agents; it is replaced only with an equal amount of PET. See Table 1 for specific formulations.

[0062] Comparative Example 2

[0063] It contains reactive interface toughening agents and nano-reinforcing fillers, but no crosslinking agents. The specific formulation is shown in Table 1.

[0064] Comparative Example 3

[0065] The reactive interface toughening agent was replaced with an equal amount of non-reactive ethylene-vinyl acetate copolymer (EVA), as shown in Table 1.

[0066] Performance testing

[0067] The above specimens were tested according to national standards: tensile strength (GB / T 1040.2-2006), bending performance (GB / T 9341-2008), notched impact strength of simply supported beam (GB / T 1043.1-2008), and heat distortion temperature (1.8 MPa, GB / T 1634.2-2004).

[0068] The results are shown in Table 2.

[0069] Table 2 Performance test results of Examples 1-3 and Comparative Examples 1-3

[0070] Based on the results in Table 2, we can conclude that: 1) Compared with Comparative Example 1 (pure PET), the composite material of the present invention has achieved a leapfrog improvement in all performance indicators, especially the notched impact strength, which has been increased by 4-6 times. At the same time, the strength and heat resistance have been greatly improved, and the "rigid-tough balance" has been perfectly achieved.

[0071] 2. Comparing Example 3 with Comparative Example 2, the tensile strength, flexural modulus and heat distortion temperature of the material decreased significantly after the rigid cross-linking network was missing, which proves the key role of the rigid cross-linking network in improving the load-bearing capacity and heat resistance of the material.

[0072] 3) Comparing Example 3 and Comparative Example 3, when non-reactive EVA was used instead of reactive E-MA-GMA, although the same nano-reinforcing filler and crosslinking agent were contained, the notched impact strength of the material decreased sharply (from 19 to 12 kJ / m). 2 Furthermore, the tensile strength decreased. This demonstrates that the chemically bonded flexible interface constructed via E-MA-GMA is the core mechanism by which this invention achieves efficient toughening and strong interfacial bonding; simple physical blending cannot achieve the same effect.

[0073] Therefore, this invention successfully solves the industry problem of balancing strength and toughness in PET materials through innovative reactive interface toughening mechanism and multi-level structural design. The resulting modified PET composite material has excellent comprehensive performance, mature process, and broad industrial application prospects.

[0074] 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 modified PET composite material based on reactive interface toughening, characterized in that, The preparation raw materials include the following parts by weight: 100 parts PET resin; 5-15 parts reactive interface toughening agent; 1-5 parts nano-reinforcing filler; 0.5-3.0 parts crosslinking agent; 3-12 parts core-shell toughening agent; 0.3-2.0 parts crystallization promoter; 0.5-2.0 parts processing aid; The reactive interface toughening agent contains epoxy groups; The nano-reinforced filler is an amino-modified reinforced filler.

2. The modified PET composite material according to claim 1, characterized in that, The reactive interfacial toughening agent is an ethylene-acrylate copolymer containing epoxy functional groups.

3. The modified PET composite material according to claim 1, characterized in that, The nano-reinforced filler is aminosilane coupling agent modified nano-silica.

4. The modified PET composite material according to claim 1, characterized in that, The crosslinking agent is dicyclopentadiene diepoxide.

5. The modified PET composite material according to claim 1, characterized in that, The core-shell toughening agent is an acrylate-based core-shell copolymer.

6. The modified PET composite material according to claim 1, characterized in that, The crystallization promoter is an organophosphate nucleating agent or nano-hydroxyapatite.

7. The modified PET composite material according to claim 1, characterized in that, The processing aids include antioxidants and lubricants.

8. A method for preparing the modified PET composite material according to any one of claims 1 to 7, characterized in that, Includes the following steps: A reactive interface toughening agent, nano-reinforcing filler, partial crosslinking agent and crystallization accelerator are mixed. The resulting mixture is then melt-blended with PET resin and extruded and granulated to obtain a pre-grafted reinforced toughening masterbatch. The pre-grafted reinforced and toughened masterbatch is mixed with the core-shell toughening agent, the remaining crosslinking agent and processing aids, and then subjected to a second melt blending, followed by extrusion granulation and injection molding to obtain the modified PET composite material.

9. The preparation method according to claim 8, characterized in that, The temperature of the first melt blend is 230~260°C, and the screw speed is 200~400 rpm; the temperature of the second melt blend is 240~270°C, and the screw speed is 250~350 rpm; the barrel temperature of the injection molding is 240~280°C, and the mold temperature is 120~140°C.

10. The application of the modified PET composite material according to any one of claims 1 to 7 or the modified PET composite material prepared by the preparation method according to any one of claims 8 to 9 in the fields of automotive parts, electronic and electrical components or high-end structural parts.

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