High-strength insulating PET composite material, its preparation method and application in insulating cover

Abstract

This invention discloses a high-strength insulating PET composite material, its preparation method, and its application in insulating covers, relating to the field of polyethylene terephthalate (PET) technology. The high-strength insulating PET composite material comprises the following raw materials in parts by weight: PET resin: 50-70 parts, glass fiber: 20-30 parts, inorganic insulating filler: 5-15 parts, compatibilizer: 1-3 parts, antioxidant: 0.2-0.8 parts, and modified flame-retardant reinforcing agent: 5-8 parts. The high-strength insulating PET composite material prepared by this invention exhibits good tensile strength, notched impact strength, flame retardant properties, and insulation properties.

Description

Technical Field

[0001] This invention relates to the field of polyethylene terephthalate (PET) technology, specifically to a high-strength insulating PET composite material, its preparation method, and its application in insulating covers. Background Technology

[0002] Polyethylene terephthalate (PET) is an engineering plastic with excellent comprehensive properties, including high mechanical strength, good dimensional stability, excellent electrical insulation, and good heat and chemical corrosion resistance. Therefore, it is widely used in electrical insulation components, electronic and electrical appliance housings, and various structural parts, especially in insulating covers and housings of electrical equipment. However, pure PET material still has certain limitations in practical applications. First, PET is a flammable polymer with a low limiting oxygen index, making it prone to combustion or dripping under high temperatures or the thermal environment generated by long-term operation of electrical equipment. This makes it difficult to meet the stringent requirements of electrical equipment for flame retardancy and safety. Therefore, it is usually necessary to modify it by adding flame retardants. However, while traditional flame retardants improve the flame retardancy of the material, they often adversely affect the material's mechanical properties, thermal stability, and electrical insulation properties, and may even increase the material's brittleness, affecting its reliability in related products.

[0003] On the other hand, to further improve the strength and rigidity of PET materials, industrial manufacturers often modify them by adding reinforcing materials such as glass fibers and inorganic fillers. However, the PET matrix is ​​a polar polyester structure, while common inorganic fillers or flame retardant particles have high surface energy and significant polarity differences, resulting in poor dispersion and weak interfacial bonding in the PET matrix. This leads to insufficient compatibility of the material system and makes it prone to agglomeration and interfacial debonding. This not only weakens the effect of reinforcing fillers on improving the mechanical properties of the material but also affects the uniformity of the overall material structure, thereby reducing the mechanical properties and long-term stability of the composite material. Furthermore, the poor compatibility between flame retardants and the PET matrix can also lead to flame retardant migration or precipitation, affecting the durability of the material.

[0004] Chinese invention patent CN118652526A discloses a aramid fiber and glass fiber modified PET composite material and its preparation method. The aramid fiber and glass fiber modified PET composite material includes the following raw materials in parts by weight: 40-60 parts PET, 4-8 parts aramid fiber, 20-30 parts glass fiber, 5-15 parts polytetrafluoroethylene, 5-9 parts flame retardant, 4-8 parts toughening agent, 0.3-1 part nucleating agent, 0.3-1 part crystallization promoter, and 0.4-1 part antioxidant. The PET composite material prepared by this invention has excellent high temperature resistance and heat aging resistance, but its flame retardant properties need to be improved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a high-strength insulating PET composite material, its preparation method, and its application in insulating covers.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A high-strength insulating PET composite material, comprising the following raw materials in parts by weight: PET resin: 50-70 parts, glass fiber: 20-30 parts, inorganic insulating filler: 5-15 parts, compatibilizer: 1-3 parts, antioxidant: 0.2-0.8 parts, modified flame retardant reinforcing agent: 5-8 parts; The compatibilizer has the following structural formula: ; The modified flame retardant reinforcing agent has the following structural formula:

[0007] The compatibilizer is prepared by the following method: S1: Polyethylene glycol monosuccinate reacts with 3-isocyanate-propyltriethoxysilane to generate intermediate A. S2: Intermediate A reacts with tris(2-aminoethyl)amine to form a compatibilizer.

[0008] The modified flame retardant reinforcing agent is prepared by the following method: A1: Eugenol reacts with (R)-6,8-dimercaptooctanoic acid to form intermediate 1. A2: Intermediate 1, paraformaldehyde reacts with 2-aminoquinazoline to generate intermediate 2. A3: Diethanolamine, paraformaldehyde, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide react to form intermediate 3. A4: Intermediate 2 reacts with intermediate 3 to generate a modified flame retardant reinforcing agent.

[0009] In step S1, the molar ratio of polyethylene glycol monosuccinate to 3-isocyanate-propyltriethoxysilane is 1:(1.02-1.04).

[0010] In step S2, the molar ratio of intermediate A to tris(2-aminoethyl)amine is (3.03-3.05):1.

[0011] In step A1, the molar ratio of eugenol to (R)-6,8-dimercaptooctanoic acid is 2.05:1.

[0012] In step A2, the molar ratio of intermediate 1 to 2-aminoquinazoline is 1:2.08.

[0013] In step A3, the molar ratio of diethanolamine to 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1.02; in step A4, the molar ratio of intermediate 2 to intermediate 3 is 2.04:1.

[0014] The inorganic insulating filler is composed of aluminum oxide and boron nitride mixed in a mass ratio of 2:3; the antioxidant is Irganox 1010.

[0015] A method for preparing a high-strength insulating PET composite material includes the following steps: (1) Weigh the following by weight: PET resin: 50-70 parts, glass fiber: 20-30 parts, inorganic insulating filler: 5-15 parts, compatibilizer: 1-3 parts, antioxidant: 0.2-0.8 parts, modified flame retardant reinforcing agent: 5-8 parts; (2) PET resin, glass fiber, inorganic insulating filler, compatibilizer, antioxidant, and modified flame retardant reinforcing agent are added to a high-speed mixer in sequence, stirred and mixed, and then conveyed to a twin-screw extruder for melt mixing; cooled and pelletized to obtain the final product.

[0016] Application of a high-strength insulating PET composite material in insulating covers.

[0017] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include: The high-strength insulating PET composite material prepared by this invention has good tensile strength, notched impact strength, flame retardant properties and insulation properties. Detailed Implementation

[0018] The following description, in conjunction with specific embodiments, provides further details, but the present invention is not limited to these embodiments.

[0019] Example 1: Preparation of compatibilizer: S1: Under nitrogen protection, 250 ml of anhydrous toluene and 0.1 mol of polyethylene glycol monosuccinate were added to a reaction flask and stirred until well mixed. Then, 0.5 g of dibutyltin dilaurate was added, and the mixture was stirred at room temperature for 10 min. The temperature was then raised to 60 °C, and 0.102 mol of 3-isocyanatopropyltriethoxysilane was slowly added dropwise over 40 min. After the addition was complete, the reaction was allowed to proceed for 6 h. The mixture was then cooled to room temperature and rotary evaporated at 65 °C to constant weight. 200 ml of petroleum ether was added and stirred to precipitate the precipitate. The precipitate was filtered, washed twice with petroleum ether (50 ml each time), and dried under vacuum at 40 °C for 12 h to obtain intermediate A. The reaction equation is shown below:

[0020] Its 1H NMR data are as follows: 1H NMR (400 MHz, Chloroform- d ) δ 11.19 (s, 1H), 4.87 (t, J = 5.1 Hz, 1H), 4.31 (dt, J = 6.7, 5.1 Hz, 4H), 3.82 (q, J = 7.5Hz, 6H), 3.74 (td, J = 5.2, 3.5 Hz, 4H), 3.70 – 3.66 (m, 8H), 3.16 (td, J =6.7, 5.1 Hz, 2H), 2.65 – 2.51 (m, 4H), 1.65 (tt, J = 9.1, 6.7 Hz, 2H), 1.21(t, J = 7.5 Hz, 9H), 0.75 (t, J = 9.0 Hz, 2H); HRMS (m / z): 542.2558 [M+H] + .

[0021] S2: Under nitrogen protection, 800 ml of anhydrous toluene, 0.303 mol of intermediate A, 0.31 mol of DCC (N,N'-dicyclohexylcarbodiimide), and 0.01 mol of DMAP (4-dimethylaminopyridine) were added to a reaction flask. The mixture was stirred for 10 min, and then 0.1 mol of tris(2-aminoethyl)amine was added. The reaction was carried out at room temperature for 12 h. The mixture was filtered, and the solution was rotary evaporated at 70 °C to constant weight. The solution was purified by silica gel column chromatography (eluting with ethyl acetate / petroleum ether (V / V=2:1), rotary evaporated at 50 °C to constant weight, and dried under vacuum at 50 °C for 12 h to obtain the compatibilizer. The reaction equation is shown below: Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d) δ 7.06 (t, J = 4.5Hz, 3H), 4.88 (t, J = 5.0 Hz, 3H), 4.30 (dt, J = 7.1, 5.2 Hz, 12H), 3.81 (q,J = 7.6 Hz, 18H), 3.73 (td, J = 5.1, 3.3 Hz, 12H), 3.69 – 3.65 (m, 24H), 3.26 (td, J = 5.4, 4.5 Hz, 6H), 3.15 (td, J = 6.8, 5.0 Hz, 6H), 2.72 (t, J = 5.4Hz, 6H), 2.66 – 2.58 (m, 6H), 2.56 – 2.49 (m, 6H), 1.64 (tt, J = 9.2, 6.6 Hz, 6H), 1.20 (t, J = 7.4 Hz, 27H), 0.76 (t, J = 8.9 Hz, 6H); HRMS (m / z):1716.8873[M+H] + .

[0022] Example 2: Preparation of compatibilizer: S1: Under nitrogen protection, 250 ml of anhydrous toluene and 0.1 mol of polyethylene glycol monosuccinate were added to the reaction flask and stirred until well mixed. Then, 0.5 g of dibutyltin dilaurate was added and stirred at room temperature for 10 min. The temperature was raised to 65 °C, and 0.103 mol of 3-isocyanatopropyltriethoxysilane was slowly added dropwise over 40 min. After the addition was complete, the reaction was allowed to proceed for 5.5 h. The mixture was cooled to room temperature and rotary evaporated at 65 °C to constant weight. 200 ml of petroleum ether was added and stirred to precipitate the precipitate. The precipitate was filtered, washed twice with petroleum ether (50 ml each time), and dried under vacuum at 40 °C for 12 h to obtain intermediate A. S2: Under nitrogen protection, 800 ml of anhydrous toluene, 0.304 mol of intermediate A, 0.31 mol of DCC and 0.01 mol of DMAP were added to the reaction flask and stirred for 10 min. Then, 0.1 mol of tris(2-aminoethyl)amine was added and the reaction was carried out at room temperature for 13 h. The mixture was filtered, and the mixture was rotary evaporated at 70 °C to constant weight. The mixture was purified by silica gel column chromatography (eluting agent was ethyl acetate / petroleum ether (V / V=2:1), rotary evaporated at 50 °C to constant weight, and vacuum dried at 50 °C for 12 h to obtain the compatibilizer.

[0023] Example 3: Preparation of compatibilizer: S1: Under nitrogen protection, 250 ml of anhydrous toluene and 0.1 mol of polyethylene glycol monosuccinate were added to the reaction flask and stirred until well mixed. Then, 0.5 g of dibutyltin dilaurate was added and stirred at room temperature for 10 min. The temperature was raised to 70 °C, and 0.104 mol of 3-isocyanopropyltriethoxysilane was slowly added dropwise over 40 min. After the addition was complete, the reaction was allowed to proceed for 5 h. The mixture was cooled to room temperature and rotary evaporated at 65 °C to constant weight. 200 ml of petroleum ether was added and stirred to precipitate the precipitate. The precipitate was filtered, washed twice with petroleum ether (50 ml each time), and dried under vacuum at 40 °C for 12 h to obtain intermediate A. S2: Under nitrogen protection, 800 ml of anhydrous toluene, 0.305 mol of intermediate A, 0.31 mol of DCC and 0.01 mol of DMAP were added to the reaction flask and stirred for 10 min. Then, 0.1 mol of tris(2-aminoethyl)amine was added and the reaction was carried out at room temperature for 14 h. The mixture was filtered, and the mixture was rotary evaporated at 70 °C to constant weight. The mixture was purified by silica gel column chromatography (eluting agent was ethyl acetate / petroleum ether (V / V=2:1), rotary evaporated at 50 °C to constant weight, and vacuum dried at 50 °C for 12 h to obtain the compatibilizer.

[0024] Example 4: Preparation of modified flame retardant reinforcing agent: A1: Under nitrogen protection, add 500 ml of tetrahydrofuran, 0.1 mol of (R)-6,8-dimercaptooctanoic acid, 0.205 mol of eugenol, and 0.8 g of photoinitiator TPO to the reaction flask, stir and mix well, and incubate at room temperature with an intensity of 8.4 mW / cm². 2 After irradiation under a 365nm UV LED lamp for 2 hours, the mixture was rotary evaporated at 40℃ to constant weight. The solution was then slowly added to 250ml of cold n-hexane, stirred, and a precipitate formed. The precipitate was filtered, washed three times with 50ml of cold n-hexane each time, and dried under vacuum at 40℃ for 12 hours to obtain intermediate 1. The reaction equation is shown below: Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ 10.33 (s, 1H), 6.75 – 6.62 (m, 6H), 6.56 (s, 2H), 3.85 (s, 6H), 2.91 – 2.83 (m, 1H), 2.75 –2.30 (m, 12H), 1.89 – 1.76 (m, 5H), 1.71 – 1.26 (m, 7H); HRMS (m / z):537.2268[M+H] + .

[0025] A2: Under nitrogen protection, 600 ml of toluene, 0.1 mol of intermediate 1, and 6 g of paraformaldehyde were added to a reaction flask. The mixture was stirred and heated to 80 °C and reacted for 1 h. Then, 0.208 mol of 2-aminoquinazoline was added, stirred and mixed, and the mixture was heated to 100 °C and reacted for 8 h. After cooling to room temperature, 0.5 M dilute hydrochloric acid solution was slowly added dropwise to adjust the pH to 7. The mixture was then rotary evaporated at 60 °C to constant weight. The precipitate was slowly added to 600 ml of cold acetone, stirred, and filtered. The precipitate was washed three times with cold acetone (50 ml each time) and dried under vacuum at 60 °C for 12 h to obtain intermediate 2. The reaction equation is shown below: Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ 10.34 (s, 1H), 8.85 (dt, J = 2.0, 1.5 Hz, 2H), 7.99 (ddt, J = 8.1, 2.1, 1.5 Hz, 2H), 7.91(dddd, J = 9.4, 2.9, 2.2, 1.5 Hz, 2H), 7.70 (td, J = 8.0, 1.2 Hz, 2H), 7.46(dddd, J = 9.5, 7.8, 3.5, 1.2 Hz, 2H), 6.82 (dp, J = 2.6, 1.8 Hz, 2H), 6.64(dt, J = 2.2, 1.9 Hz, 2H), 5.72 (s, 4H), 4.72 (d, J = 2.1 Hz, 4H), 3.87 (s,6H), 2.92 – 2.81 (m, 1H), 2.71 – 2.59 (m, 6H), 2.57 – 2.46 (m, 4H), 2.38 –2.31 (m, 2H), 1.88 – 1.75 (m, 5H), 1.72 – 1.28 (m, 7H); HRMS (m / z):875.3547[M+H] + .

[0026] A3: Under nitrogen protection, 200 ml of 1,4-dioxane, 0.1 mol of diethanolamine, and 3.2 g of paraformaldehyde were added to a reaction flask. The mixture was stirred and mixed thoroughly, and the temperature was raised to 80 °C. The reaction was allowed to proceed for 1 h. Then, 0.102 mol of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added. The mixture was stirred and mixed thoroughly, and the reaction was allowed to proceed for 3 h. The mixture was then rotary evaporated at 60 °C to constant weight. The precipitate was slowly added to 150 ml of cold diethyl ether, stirred, and filtered. The precipitate was washed three times with cold diethyl ether (50 ml each time) and dried under vacuum at 60 °C for 12 h to obtain intermediate 3. The reaction equation is shown below: Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ 8.24(dd, J = 7.3,1.2 Hz, 1H), 8.13 (dd, J = 7.0, 1.3 Hz, 1H), 7.94 – 7.89 (m, 1H), 7.73 (td, J= 7.1, 1.3 Hz, 1H), 7.61 (td, J = 7.2, 1.5 Hz, 1H), 7.47 – 7.41 (m, 3H), 3.73– 3.62 (m, 8H), 2.85 (t, J = 5.0 Hz, 4H); HRMS (m / z):334.1135[M+H] + .

[0027] A4: Under nitrogen protection, 800 ml of toluene, 0.204 mol of intermediate 2, 0.21 mol of dicyclohexylcarbodiimide, and 0.01 mol of 4-dimethylaminopyridine were added to a reaction flask. The mixture was stirred for 15 min, then 0.1 mol of intermediate 3 was added. The reaction was carried out at 25 °C for 10 h. After filtration, the mixture was rotary evaporated at 60 °C to constant weight. The mixture was purified by silica gel column chromatography (using an ethyl acetate / methanol mixture as eluent, with a gradient elution at a volume ratio of 10:1 to 5:1). The mixture was rotary evaporated at 50 °C to constant weight to obtain the modified flame retardant enhancer. The reaction equation is shown below: Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d) δ 8.84 (dt, J =1.9, 1.6 Hz, 4H), 8.25 (dd, J = 7.4, 1.3 Hz, 1H), 8.12 (dd, J = 7.1, 1.4 Hz, 1H), 7.98 (ddt, J = 8.0, 2.2, 1.3 Hz, 4H), 7.94 – 7.88 (m, 5H), 7.75 – 7.67(m, 5H), 7.60 (td, J = 7.3, 1.4 Hz, 1H), 7.50 – 7.41 (m, 7H), 6.83 (dp, J =2.5, 1.7 Hz, 4H), 6.63 (dt, J = 2.1, 1.8 Hz, 4H), 5.71 (s, 8H), 4.73 (d, J =2.0 Hz, 8H), 4.28 (t, J = 5.5 Hz, 4H), 3.88 (s, 12H), 3.70 (s, 2H), 3.08 (t,J = 5.5 Hz, 4H), 2.91 – 2.84 (m, 2H), 2.70 – 2.58 (m, 12H), 2.56 – 2.45 (m,8H), 2.34 – 2.29 (m, 4H), 1.89 – 1.76 (m, 10H), 1.71 – 1.52 (m, 8H), 1.50 –1.29 (m, 6H); HRMS (m / z): 2047.8049 [M+H] + .

[0028] Example 5: Preparation of high-strength insulating PET composite material: (1) Weigh out: 500g of PET resin, 200g of glass fiber, 50g of inorganic insulating filler (20g of alumina + 30g of boron nitride), 10g of compatibilizer (prepared in Example 1), 2g of antioxidant (Irganox 1010), and 50g of modified flame retardant reinforcing agent (prepared in Example 4); (2) PET resin, glass fiber, inorganic insulating filler, compatibilizer, antioxidant, and modified flame retardant reinforcing agent are added to a high-speed mixer in sequence and mixed at 90°C and 1000 rpm for 30 min. The mixture is then conveyed to a twin-screw extruder for melt mixing. The screw speed is 200 rpm, the conveying section temperature is 250°C, the melting section temperature is 260°C, the mixing section temperature is 270°C, and the homogenization section temperature is 265°C. After cooling and pelletizing, high-strength insulating PET composite material is obtained.

[0029] Example 6: Preparation of high-strength insulating PET composite material: (1) Weigh: 600g PET resin, 250g glass fiber, 100g inorganic insulating filler (40g alumina + 60g boron nitride), 20g compatibilizer (prepared in Example 2), 5g antioxidant (Irganox 1010), and 60g modified flame retardant reinforcing agent (prepared in Example 4); (2) PET resin, glass fiber, inorganic insulating filler, compatibilizer, antioxidant, and modified flame retardant reinforcing agent are added to a high-speed mixer in sequence and mixed at 90°C and 1000 rpm for 30 min. The mixture is then conveyed to a twin-screw extruder for melt mixing. The screw speed of the twin-screw extruder is 200 rpm. The temperature of the conveying section of the twin-screw extruder is 250°C, the temperature of the melting section is 260°C, the temperature of the mixing section is 270°C, and the temperature of the homogenization section is 265°C. The mixture is then cooled and pelletized to obtain a high-strength insulating PET composite material.

[0030] Example 7: Preparation of high-strength insulating PET composite material: (1) Weigh: 700g PET resin, 300g glass fiber, 150g inorganic insulating filler (60g alumina + 90g boron nitride), 30g compatibilizer (prepared in Example 3), 8g antioxidant (Irganox 1010), and 80g modified flame retardant reinforcing agent (prepared in Example 4); (2) PET resin, glass fiber, inorganic insulating filler, compatibilizer, antioxidant, and modified flame retardant reinforcing agent are added to a high-speed mixer in sequence and mixed at 90°C and 1000 rpm for 30 min. The mixture is then conveyed to a twin-screw extruder for melt mixing. The screw speed of the twin-screw extruder is 200 rpm. The temperature of the conveying section of the twin-screw extruder is 250°C, the temperature of the melting section is 260°C, the temperature of the mixing section is 270°C, and the temperature of the homogenization section is 265°C. The mixture is then cooled and pelletized to obtain a high-strength insulating PET composite material.

[0031] Comparative Example 1 The raw material composition and process of the high-strength insulating PET composite material are basically the same as those in Example 6, except that the compatibilizer is replaced with an equal weight of a compatibilizer prepared by the following method: The preparation method of the compatibilizer is basically the same as that in Example 2, except that the polyethylene glycol monosuccinate in step S1 is replaced with an equimolar amount of hydroxyl-polyethylene glycol-carboxyl groups (number average molecular weight of 500).

[0032] Comparative Example 2 The raw material composition and process of the high-strength insulating PET composite material are basically the same as those in Example 6, except that the compatibilizer is replaced with an equal weight of a compatibilizer prepared by the following method: The preparation method of the compatibilizer is basically the same as that in Example 2, except that the 3-isocyanate-propyltriethoxysilane in step S1 is replaced with an equimolar amount of 3-isocyanate-propylmethyldiethoxysilane.

[0033] Comparative Example 3 The raw material composition and process of the high-strength insulating PET composite material are basically the same as those in Example 6, except that the compatibilizer is replaced with an equal weight of a compatibilizer prepared by the following method: The preparation method of the compatibilizer is basically the same as that in Example 2, except that the tris(2-aminoethyl)amine in step S2 is replaced with an equimolar amount of 1,4-butanediamine, and the amount of intermediate A is 0.204 mol.

[0034] Comparative Example 4 The raw material composition and process of the high-strength insulating PET composite material are basically the same as those in Example 6, except that the modified flame retardant reinforcing agent is replaced with an equal weight of the modified flame retardant reinforcing agent prepared by the following method: The preparation method of the modified flame retardant reinforcing agent is basically the same as that in Example 4, except that (R)-6,8-dimercaptooctanoic acid in step A1 is replaced with an equimolar amount of 8-mercaptooctanoic acid, the amount of eugenol in step A1 is 0.105 mol, and the amount of 2-aminoquinazoline in step A2 is 0.108 mol.

[0035] Comparative Example 5 The raw material composition and process of the high-strength insulating PET composite material are basically the same as those in Example 6, except that the modified flame retardant reinforcing agent is replaced with an equal weight of the modified flame retardant reinforcing agent prepared by the following method: The preparation method of the modified flame retardant reinforcing agent is basically the same as that in Example 4, except that 2-aminoquinazoline in step A2 is replaced with an equimolar amount of 2-aminopyrimidine.

[0036] Comparative Example 6 The raw material composition and process of the high-strength insulating PET composite material are basically the same as those in Example 6, except that the modified flame retardant reinforcing agent is replaced with an equal weight of the modified flame retardant reinforcing agent prepared by the following method: The preparation method of the modified flame retardant reinforcing agent is basically the same as that in Example 4, except that the diethanolamine in step A3 is replaced with an equimolar amount of 3-(methylamino)-1-propanol, and the amount of intermediate 2 fed in step A4 is 0.104 mol.

[0037] Comparative Example 7 The raw material composition and process of the high-strength insulating PET composite material are basically the same as those in Example 6, except that the modified flame retardant reinforcing agent is replaced with an equal weight of the modified flame retardant reinforcing agent prepared by the following method: The preparation method of the modified flame retardant reinforcing agent is basically the same as that in Example 4, except that 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step A3 is replaced with an equimolar amount of diphenylphosphine.

[0038] The PET resin used in the embodiments and comparative examples of this application is model BG802; the glass fiber is model EWR2000, produced by Taishan Glass Fiber Co., Ltd.; the paraformaldehyde is purchased from Maclean, item number P804536-500g, reagent grade; the alumina has an average particle size of 50μm, produced by Zibo Honghe Chemical Co., Ltd.; and the boron nitride has a D50 of 10μm, produced by Suzhou Napo Materials Technology Co., Ltd.

[0039] The tensile strength, notched impact strength, limiting oxygen index, and volume resistivity of the high-strength insulating PET composite materials prepared in the examples and comparative examples were tested, and the test results are shown in Table 1.

[0040] Sample preparation: The high-strength insulating PET composite materials prepared in Examples 5-7 and Comparative Example 17 were placed in a forced-air drying oven and dried at 80°C for 12 hours. After drying, the high-strength insulating PET composite materials were molded into test samples using an injection molding machine. The parameters of each section of the injection molding machine were set as follows: the temperatures of zones one to five were set to 240°C, 245°C, 260°C, 270°C, and 265°C; the injection speed was 3.6 cm. 3 / s; the injection pressure is 80MPa, and the holding pressure is 80% of the injection pressure.

[0041] Tensile strength test: The tensile strength test shall be carried out in accordance with GB / T 1447-2005, using type II specimens, and the tensile speed shall be 5 mm / min.

[0042] Notched impact strength test: The notched impact strength test shall be conducted in accordance with GB / T 1843-2008, and the notch type shall be type A.

[0043] Limiting oxygen index test: According to GB / T 2406.2-2009, the limiting oxygen index was tested using a JF-3 oxygen index tester with method A - top surface ignition method. The sample shape was type I, and the sample size was 120mm×10mm×10mm.

[0044] Volume resistivity: Volume resistivity was tested in accordance with GB / T 1410-2006.

[0045] Table 1 Performance Test Data of High-Strength Insulating PET Composite Material As can be seen from Table 1, the high-strength insulating PET composite materials prepared in Examples 5-7 of this application have good tensile strength, notched impact strength, flame retardant properties and insulation properties.

[0046] The compatibilizer prepared in this application is centered on a tertiary amine, with three long polyethylene glycol chains linked by amide bonds. Each chain's end is connected to a triethoxysilane group via a urethane bond. During melt processing, the terminal triethoxysilane group hydrolyzes to generate silanol, which undergoes a condensation reaction with the silanol groups on the glass fiber surface and inorganic insulating fillers (such as alumina) to form covalent bonds. This enhances the interfacial adhesion between the filler and the matrix, effectively transferring stress under external force and improving tensile strength. The amide bonds have strong polarity and can undergo hydrogen bonding and dipole interactions with the ester groups in the PET molecular chain, enabling the compatibilizer to form multiple interfacial interaction sites in the matrix. Simultaneously, the three-armed polyethylene glycol chains can form segmental entanglements with the PET molecular chains, thus forming a stable physical interaction network in the system. Under external force, this effectively restricts molecular chain slippage and improves interfacial stress transfer efficiency, thereby enhancing the overall stability of the material system and improving its impact resistance. The synergistic effect of multiple functional groups enables this compatibilizer to build a strong and flexible interfacial transition layer between the PET matrix and the reinforcing filler, thereby effectively improving toughness while maintaining rigidity, and achieving a simultaneous improvement in the tensile strength and impact resistance of the composite material.

[0047] The compatibilizer prepared in Comparative Example 2 used 3-propyl isocyanate methyl diethoxysilane with one less ethoxy group, which reduced the number of hydrolyzable groups at the end of the compatibilizer. This weakened the compatibilizer's ability to form covalent bonds with the glass fiber and inorganic filler surfaces, decreased the interfacial bonding force, and thus reduced the tensile strength and impact resistance of the composite material.

[0048] The modified flame retardant reinforcing agent prepared in this application is based on 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and incorporates multiple functional groups such as thioether bonds, eugenol benzene rings, and quinazoline structures. The P=O and POC functional groups contained in the modified flame retardant reinforcing agent can generate phosphoric acid substances during material combustion, promoting the dehydration and carbonization of the PET matrix to form a dense and stable carbon layer, thereby effectively isolating heat and oxygen and achieving condensed phase flame retardancy. Simultaneously, the quinazoline structure contains nitrogen-containing heterocycles, which can release inert gases during thermal decomposition and participate in the expansion and stabilization of the carbon layer structure, forming a PN synergistic flame retardant system with the phosphorus-based structure, further improving the limiting oxygen index of the material. Secondly, the eugenol benzene ring and sulfide segments endow the molecule with both rigidity and flexibility. The eugenol benzene ring enhances molecular rigidity and forms π-π stacking with the PET aromatic ring, promoting compatibility and uniform dispersion. The flexible sulfide bonds reduce interfacial rigidity differences, improve stress dispersion, and inhibit crack propagation, thereby enhancing tensile strength and notched impact strength. The multi-arm structure bridged by ester bonds achieves multi-point anchoring, further strengthening the filler-matrix interface bonding and preventing flame retardant migration and precipitation. The synergistic flame retardant effect of phosphorus, nitrogen, and sulfur elements, combined with the multifunctional interfacial reinforcement effect, enables this modified flame retardant to significantly improve the mechanical properties of PET composites while enhancing their flame retardant performance.

[0049] In Comparative Example 5, replacing 2-aminoquinazoline with 2-aminopyrimidine reduced the rigidity of the molecular skeleton, leading to a decrease in mechanical properties. Simultaneously, the molecular thermal stability and char-forming ability decreased, weakening the char barrier effect and resulting in reduced flame retardant properties.

[0050] The diphenylphosphine used in Comparative Example 7 lacks a stable P=O structure, resulting in weakened char-forming promoting ability and reduced density of the char layer, leading to decreased flame retardant properties. Simultaneously, the low polarity of diphenylphosphine weakens its compatibility with the PET matrix and interfacial interactions, hindering stress transfer and reducing the material's mechanical properties.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention based on the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A high-strength insulating PET composite material, characterized in that, The ingredients include the following parts by weight: PET resin: 50-70 parts, glass fiber: 20-30 parts, inorganic insulating filler: 5-15 parts, compatibilizer: 1-3 parts, antioxidant: 0.2-0.8 parts, modified flame retardant reinforcing agent: 5-8 parts; The compatibilizer has the following structural formula: ； The modified flame retardant reinforcing agent has the following structural formula: 。 2. The high-strength insulating PET composite material according to claim 1, characterized in that, The compatibilizer is prepared by the following method: S1: Polyethylene glycol monosuccinate reacts with 3-isocyanate-propyltriethoxysilane to generate intermediate A. S2: Intermediate A reacts with tris(2-aminoethyl)amine to form a compatibilizer.

3. The high-strength insulating PET composite material according to claim 1, characterized in that, The modified flame retardant reinforcing agent is prepared by the following method: A1: Eugenol reacts with (R)-6,8-dimercaptooctanoic acid to form intermediate 1. A2: Intermediate 1, paraformaldehyde reacts with 2-aminoquinazoline to generate intermediate 2. A3: Diethanolamine, paraformaldehyde, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide react to form intermediate 3. A4: Intermediate 2 reacts with intermediate 3 to generate a modified flame retardant reinforcing agent.

4. The high-strength insulating PET composite material according to claim 2, characterized in that, In step S1, the molar ratio of polyethylene glycol monosuccinate to 3-isocyanate-propyltriethoxysilane is 1:(1.02-1.04).

5. The high-strength insulating PET composite material according to claim 2, characterized in that, In step S2, the molar ratio of intermediate A to tris(2-aminoethyl)amine is (3.03-3.05):

1.

6. The high-strength insulating PET composite material according to claim 3, characterized in that, In step A1, the molar ratio of eugenol to (R)-6,8-dimercaptooctanoic acid is 2.05:

1.

7. The high-strength insulating PET composite material according to claim 3, characterized in that, In step A2, the molar ratio of intermediate 1 to 2-aminoquinazoline is 1:2.08; in step A3, the molar ratio of diethanolamine to 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1.02; in step A4, the molar ratio of intermediate 2 to intermediate 3 is 2.04:

1.

8. The high-strength insulating PET composite material according to claim 1, characterized in that, The inorganic insulating filler is composed of aluminum oxide and boron nitride mixed in a mass ratio of 2:3; the antioxidant is Irganox 1010.

9. A method for preparing the high-strength insulating PET composite material according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Weigh the following by weight: PET resin: 50-70 parts, glass fiber: 20-30 parts, inorganic insulating filler: 5-15 parts, compatibilizer: 1-3 parts, antioxidant: 0.2-0.8 parts, modified flame retardant reinforcing agent: 5-8 parts; (2) PET resin, glass fiber, inorganic insulating filler, compatibilizer, antioxidant, and modified flame retardant reinforcing agent are added to a high-speed mixer in sequence, stirred and mixed, and then conveyed to a twin-screw extruder for melt mixing; cooled and pelletized to obtain the final product.

10. The application of the high-strength insulating PET composite material according to any one of claims 1-8 in an insulating cover.

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