A foamed PET sheet and its preparation method

Abstract

This invention relates to a foamed PET sheet and its preparation method, belonging to the field of composite material technology. Using polyethylene terephthalate (PET), a foaming agent, an antioxidant, zinc oxide, a lubricant, and modified glass fiber as raw materials, this invention prepares a short glass fiber reinforced PET foam material. The invention obtains the short glass fiber reinforced PET foam material by co-extruding the raw materials, followed by cooling, traction, granulation, and injection molding. The preparation method of this invention improves the proportions of the raw materials and prepares a modified glass fiber, solving the problem of uneven dispersion of the nucleating agent during PET foaming, and improving the interfacial compatibility between the glass fiber and the PET foam material, thus reducing the risk of stress cracking.

Description

Technical Field

[0001] This invention belongs to the field of PET material technology, specifically, it relates to a foamed PET sheet and its preparation method. Background Technology

[0002] Polyethylene terephthalate (PET) foam is a porous functional material prepared through physical or chemical foaming processes based on PET. The closed-cell structure of PET foam not only provides excellent thermal and sound insulation performance but also exhibits superior compressive strength and energy absorption characteristics, with an energy absorption efficiency more than 40% higher than polystyrene. It can quickly recover its original shape after impact without irreversible deformation. Furthermore, it is lightweight and environmentally friendly, with a density lower than 0.1 g / cm³, resulting in a weight reduction of 30–70% compared to conventional plastics. It has wide applications in lightweight automotive components, precision instrument packaging, building sound and thermal insulation materials, cosmetic packaging materials, and medical device packaging.

[0003] Adding reinforcing agents such as glass fiber to PET foam materials can significantly improve their strength. However, due to the poor compatibility between fibers and PET foam materials, this may damage the closed-cell structure inside the PET foam material. In addition, the melt viscosity of the system will increase significantly after adding fibers, and the nucleating agent is prone to agglomeration in the matrix, affecting the dispersion and function of the nucleating agent. In order to improve the strength of PET foam materials while retaining their advantages, it is necessary to solve the problem of interference of added fibers on nucleating agents. Based on this, the present invention provides a foamed PET sheet and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a foamed PET sheet and its preparation method, so as to solve the problems mentioned in the background art.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A foamed PET sheet comprises the following raw materials in parts by weight: 100 parts polyethylene terephthalate, 4-7 parts foaming agent, 0.14-0.28 parts antioxidant, 0.06-0.17 parts zinc oxide, 0.4-1.2 parts lubricant, and 15-25 parts modified glass fiber;

[0007] A method for preparing foamed PET sheets includes the following steps:

[0008] Step 1: Weigh each raw material according to the specified mass fractions;

[0009] Step 2: Add polyethylene terephthalate, modified glass fiber, antioxidant, zinc oxide, lubricant, and foaming agent to a mixer and mix thoroughly to obtain a homogeneous mixture for later use.

[0010] The third step involves melting and extruding the homogeneous mixture using a twin-screw extruder, followed by cooling, traction, granulation, and injection molding to obtain short glass fiber reinforced polyethylene terephthalate foam material.

[0011] Furthermore, the antioxidant is one of antioxidant 1076, antioxidant 1010, and antioxidant 626.

[0012] Furthermore, the foaming agent is one of F-230D microspheres and F-260D microspheres.

[0013] Furthermore, the lubricant is stearic acid.

[0014] Furthermore, the temperature conditions for melt extrusion in the third step are 160-180℃, preferably 165-175℃.

[0015] Furthermore, the modified glass fiber is prepared by the following steps:

[0016] Step 1: Mix silane coupling agent KH-560, glass fiber, and anhydrous ethanol in a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 40-80℃ for 8-24 hours. After the reaction is complete, filter out the glass fiber, wash it with anhydrous ethanol, and dry it in an oven to constant weight to obtain epoxidized glass fiber.

[0017] Step 2: Under nitrogen protection, sorbitol, 4-methyl-3-nitrobenzaldehyde, p-toluenesulfonic acid, and cyclohexane are mixed in a three-necked flask. A condenser connected to a liquid-liquid separator and a thermometer are attached. Magnetic stirring is turned on, and then an equal amount of methanol is added to the three-necked flask in 3-5 batches. The reaction is carried out at 55-80℃ for 4-8 hours. During the reaction, the aqueous phase in the liquid-liquid separator is continuously separated, and the organic phase is returned to the system. After the reaction is completed, sodium hydroxide solution is added to the three-necked flask to adjust the pH to 7-8. Heating is continued to allow cyclohexane and water to evaporate azeotropically. Water is continuously added to the three-necked flask until no more cyclohexane evaporates. The mixture is then cooled to room temperature and vacuum filtered. The resulting solid is washed with hot water and purified by reflux with isopropanol to obtain the nucleating agent.

[0018] Step 3: Mix the nucleating agent, ethanol solution, and sodium sulfide in a three-necked flask, attach a condenser and a thermometer, turn on the magnetic stirrer, and react at 70-80℃ for 2-4 hours. After the reaction is complete, remove the solvent by rotary evaporation, wash the remaining solid with hot water and dry it to obtain the amination nucleating agent.

[0019] Step 4: Under nitrogen protection, the amination nucleating agent, epoxidized glass fiber, and anhydrous ethanol are mixed in a three-necked flask, equipped with a condenser and thermometer, and the magnetic stirrer is turned on. The reaction is carried out at 60-80℃ for 6-12 hours. After the reaction is completed, the glass fiber is filtered out, washed with anhydrous ethanol, and dried in an oven to constant weight to obtain modified glass fiber.

[0020] Furthermore, by mass parts, the ratio of silane coupling agent KH-560, glass fiber, and anhydrous ethanol used in step 1 is 2-4 parts: 5-10 parts: 180-240 parts.

[0021] Furthermore, by mass parts, the ratio of sorbitol, 4-methyl-3-nitrobenzaldehyde, p-toluenesulfonic acid, and cyclohexane used in step 2 is 1.3-1.5 parts: 2.3-2.7 parts: 0.02-0.05 parts: 50-120 parts.

[0022] Preferably, the total mass of methanol added in step 2 is 10-12% of the mass of cyclohexane.

[0023] Furthermore, the ethanol solution used in step 3 is an aqueous ethanol solution with a volume fraction of 10-20%.

[0024] Furthermore, by mass parts, the ratio of nucleating agent, ethanol solution, and sodium sulfide used in step 3 is 2.5-3 parts: 40-100 parts: 1.8-2.4 parts.

[0025] Furthermore, by mass parts, the ratio of amination nucleating agent, epoxidized glass fiber, and anhydrous ethanol used in step 4 is 1-2 parts: 5-10 parts: 180-240 parts.

[0026] The beneficial effects of this invention are:

[0027] This invention uses polyethylene terephthalate (PET), a foaming agent, an antioxidant, zinc oxide, a lubricant, and modified glass fiber as raw materials to prepare a short glass fiber reinforced PET foam material. The invention obtains the short glass fiber reinforced PET foam material by co-extruding the raw materials, followed by cooling, traction, granulation, and injection molding. The preparation method of this invention improves the proportions of the raw materials and prepares a modified glass fiber, solving the problem of uneven dispersion of the nucleating agent during PET foaming, and improving the interfacial compatibility between the glass fiber and the PET foam material, thus reducing the risk of stress cracking.

[0028] This invention first modifies glass fibers with a silane coupling agent KH-560, adding epoxy groups to the surface of the glass fibers. Using sorbitol and 4-methyl-3-nitrobenzaldehyde as raw materials, a nucleating agent is obtained through an acetal reaction catalyzed by p-toluenesulfonic acid. Then, sodium sulfide is used as a reducing agent to reduce the nitro group in the nucleating agent structure to an amino group, obtaining an amination nucleating agent. Finally, utilizing the easy ring-opening addition property of amino and epoxy groups, the amination nucleating agent is grafted onto the surface of epoxidized glass fibers to obtain a modified glass fiber. This invention provides a modified glass fiber... The reduced surface hydroxyl content and the loading of nucleating agents not only effectively improve the interfacial compatibility between inorganic glass fibers and polyethylene terephthalate foam materials, but also avoid the problems of uneven dispersion and agglomeration of nucleating agents caused by traditional blending methods. The surface of glass fibers grafted with nucleating agents can serve as heterogeneous nucleation sites, promoting the formation of a finer and more uniform crystal structure in polyethylene terephthalate. The nucleating agents on the surface can more effectively control the formation of bubble nuclei during the foaming process, resulting in more uniform cell distribution and smaller cell size, thereby improving the mechanical properties of the foam material. Attached Figure Description

[0029] Figure 1 This is an infrared spectrum test image of the modified glass fiber of the present invention. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A modified glass fiber is prepared by the following steps:

[0033] Step 1: According to the mass fraction, mix 4 parts of silane coupling agent KH-560, 10 parts of glass fiber, and 240 parts of anhydrous ethanol in a three-necked flask, attach a condenser and a thermometer, turn on the magnetic stirrer, and react at 80°C for 8 hours. After the reaction is completed, filter out the glass fiber, wash it with anhydrous ethanol, and dry it in an oven to constant weight to obtain epoxidized glass fiber.

[0034] Step 2: Under nitrogen protection, mix 1.5 parts by mass of sorbitol, 2.7 parts by mass of 4-methyl-3-nitrobenzaldehyde, 0.05 parts by mass of p-toluenesulfonic acid, and 120 parts by mass of cyclohexane in a three-necked flask. Attach a condenser connected to a liquid-liquid separator and a thermometer, and turn on the magnetic stirrer. Then, add equal amounts of methanol (3 parts by mass per batch, totaling 10% of the cyclohexane mass) to the three-necked flask in four batches and react at 75-80℃ for 4 hours. During this time, continuously separate the aqueous phase in the liquid-liquid separator and return the organic phase to the system. After the reaction is complete, add a 20% sodium hydroxide aqueous solution to the three-necked flask to adjust the pH to 8. Continue heating to allow the cyclohexane and water to evaporate azeotropically. Continuously add water to the three-necked flask until no more cyclohexane evaporates. Then cool to room temperature and filter under vacuum. Wash the obtained solid with hot water and reflux with isopropanol to obtain the nucleating agent.

[0035] Step 3: According to the mass fraction, mix 3 parts of nucleating agent, 40 parts of 20% ethanol aqueous solution and 2.4 parts of sodium sulfide in a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 80℃ for 2 hours. After the reaction is completed, remove the solvent by rotary evaporation, wash the remaining solid with hot water and dry to obtain the amination nucleating agent.

[0036] Step 4: Under nitrogen protection, mix 2 parts by mass of amination nucleating agent, 10 parts by mass of epoxidized glass fiber, and 240 parts by mass of anhydrous ethanol in a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 80°C for 6 hours. After the reaction is complete, filter out the glass fiber, wash it with anhydrous ethanol, and dry it in an oven to constant weight to obtain modified glass fiber.

[0037] Example 2

[0038] A modified glass fiber is prepared by the following steps:

[0039] Step 1: According to the mass fraction, mix 2 parts of silane coupling agent KH-560, 5 parts of glass fiber, and 180 parts of anhydrous ethanol in a three-necked flask, attach a condenser and a thermometer, turn on the magnetic stirrer, and react at 40°C for 24 hours. After the reaction is completed, filter out the glass fiber, wash it with anhydrous ethanol, and dry it in an oven to constant weight to obtain epoxidized glass fiber.

[0040] Step 2: Under nitrogen protection, mix 1.3 parts by mass of sorbitol, 2.3 parts by mass of 4-methyl-3-nitrobenzaldehyde, 0.02 parts by mass of p-toluenesulfonic acid, and 50 parts by mass of cyclohexane in a three-necked flask. Attach a condenser connected to a liquid-liquid separator and a thermometer. Turn on the magnetic stirrer. Then, add equal amounts of methanol (2 parts by mass per batch, totaling 12% of the cyclohexane mass fraction) to the three-necked flask in three batches. React at 55-60℃ for 8 hours, continuously separating the aqueous phase in the liquid-liquid separator and returning the organic phase to the system. After the reaction is complete, add 10% sodium hydroxide aqueous solution to the three-necked flask to adjust the pH to 7. Continue heating to allow the cyclohexane and water to evaporate azeotropically. Continuously add water to the three-necked flask until no more cyclohexane evaporates. Then cool to room temperature and filter under vacuum. Wash the obtained solid with hot water and reflux with isopropanol to obtain the nucleating agent.

[0041] Step 3: According to the mass fraction, mix 2.5 parts of nucleating agent, 100 parts of 10% ethanol aqueous solution and 1.8 parts of sodium sulfide in a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 70℃ for 4 hours. After the reaction is completed, remove the solvent by rotary evaporation, wash the remaining solid with hot water and dry to obtain the amination nucleating agent.

[0042] Step 4: Under nitrogen protection, mix 1 part amination nucleating agent, 5 parts epoxidized glass fiber, and 180 parts anhydrous ethanol in a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 60°C for 12 hours. After the reaction is complete, filter out the glass fiber, wash it with anhydrous ethanol, and dry it in an oven to constant weight to obtain modified glass fiber.

[0043] Example 3

[0044] A modified glass fiber is prepared by the following steps:

[0045] Step 1: According to the mass fraction, mix 3 parts of silane coupling agent KH-560, 7.5 parts of glass fiber, and 210 parts of anhydrous ethanol in a three-necked flask, attach a condenser and a thermometer, turn on the magnetic stirrer, and react at 60°C for 16 hours. After the reaction is completed, filter out the glass fiber, wash it with anhydrous ethanol, and dry it in an oven to constant weight to obtain epoxidized glass fiber.

[0046] Step 2: Under nitrogen protection, mix 1.4 parts by mass of sorbitol, 2.4 parts by mass of 4-methyl-3-nitrobenzaldehyde, 0.035 parts by mass of p-toluenesulfonic acid, and 85 parts by mass of cyclohexane in a three-necked flask. Attach a condenser connected to a liquid-liquid separator and a thermometer, and turn on the magnetic stirrer. Then, add equal amounts of methanol (1.87 parts by mass per batch, totaling 11% of the cyclohexane mass) to the three-necked flask in 5 batches and react at 65-70℃ for 6 hours. During this time, continuously separate the aqueous phase in the liquid-liquid separator and return the organic phase to the system. After the reaction is complete, add a 15% sodium hydroxide aqueous solution to the three-necked flask to adjust the pH to 7.5. Continue heating to allow the cyclohexane and water to evaporate azeotropically. Continuously add water to the three-necked flask until no more cyclohexane evaporates. Then cool to room temperature and filter under vacuum. Wash the obtained solid with hot water and reflux with isopropanol to obtain the nucleating agent.

[0047] Step 3: According to the mass fraction, mix 2.8 parts of nucleating agent, 70 parts of 15% ethanol aqueous solution and 2.1 parts of sodium sulfide in a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 75℃ for 3 hours. After the reaction is completed, remove the solvent by rotary evaporation, wash the remaining solid with hot water and dry to obtain the amination nucleating agent.

[0048] Step 4: Under nitrogen protection, mix 1.5 parts by mass of the amination nucleating agent, 7.5 parts by mass of the epoxidized glass fiber, and 210 parts by mass of anhydrous ethanol in a three-necked flask, attach a condenser and a thermometer, turn on the magnetic stirrer, and react at 70°C for 9 hours. After the reaction is complete, filter out the glass fiber, wash it with anhydrous ethanol, and dry it in an oven to constant weight to obtain the modified glass fiber.

[0049] Experimental Example 1

[0050] The modified glass fiber obtained in Example 1 was characterized by infrared spectroscopy. Infrared spectroscopy was performed on a Nicolet 6700 Fourier transform infrared spectrometer (Thermo Scientific) after pressing with potassium bromide tablets. Figure 1 As shown, in the range of 3300-3200cm -1 A hydroxyl absorption peak appears at 3100-3000 cm⁻¹. -1 An absorption peak for hydrogen atoms on the benzene ring appears at 1250-1100 cm⁻¹. -1 The appearance of an ether bond absorption peak indicates that the reaction has occurred successfully.

[0051] Example 4

[0052] A foamed PET sheet comprises the following raw materials in parts by weight: 100 parts polyethylene terephthalate, 4 parts F-230D microspheres, 0.14 parts antioxidant 1076, 0.06 parts zinc oxide, 0.4 parts stearic acid, and 15 parts modified glass fiber obtained in Example 1.

[0053] A method for preparing foamed PET sheets includes the following steps:

[0054] Step 1: Weigh each raw material according to the specified mass fractions;

[0055] Step 2: Add polyethylene terephthalate, the modified glass fiber obtained in Example 1, antioxidant 1076, zinc oxide, stearic acid, and F-230D microspheres to a mixer and mix thoroughly to obtain a homogeneous mixture for later use.

[0056] The third step involves melting and extruding the homogeneous mixture using a twin-screw extruder at a temperature of 160-170℃. After cooling, traction, and granulation, the mixture is then injection molded to obtain short glass fiber reinforced foamed PET sheets.

[0057] Example 5

[0058] A foamed PET sheet comprises the following raw materials in parts by weight: 100 parts polyethylene terephthalate, 5.5 parts F-230D microspheres, 0.21 parts antioxidant 1010, 0.115 parts zinc oxide, 0.8 parts stearic acid, and 20 parts modified glass fiber obtained in Example 2.

[0059] A method for preparing foamed PET sheets includes the following steps:

[0060] Step 1: Weigh each raw material according to the specified mass fractions;

[0061] Step 2: Add polyethylene terephthalate, the modified glass fiber obtained in Example 2, antioxidant 1010, zinc oxide, stearic acid, and F-230D microspheres to a mixer and mix thoroughly to obtain a homogeneous mixture for later use.

[0062] The third step involves melting and extruding the homogeneous mixture using a twin-screw extruder at a temperature of 165-175℃. After cooling, traction, and granulation, the mixture is then injection molded to obtain short glass fiber reinforced foamed PET sheets.

[0063] Example 6

[0064] A short glass fiber reinforced polyethylene terephthalate foam material comprises the following raw materials in parts by weight: 100 parts polyethylene terephthalate, 7 parts F-260D microspheres, 0.28 parts antioxidant 626, 0.17 parts zinc oxide, 1.2 parts stearic acid, and 25 parts modified glass fiber obtained in Example 3;

[0065] A method for preparing foamed PET sheets includes the following steps:

[0066] Step 1: Weigh each raw material according to the specified mass fractions;

[0067] Step 2: Add polyethylene terephthalate, the modified glass fiber obtained in Example 3, antioxidant 626, zinc oxide, stearic acid, and F-260D microspheres to a mixer and mix thoroughly to obtain a homogeneous mixture for later use.

[0068] The third step involves melting and extruding the homogeneous mixture using a twin-screw extruder at a temperature of 170-180℃. After cooling, traction, and granulation, the mixture is then injection molded to obtain short glass fiber reinforced foamed PET sheets.

[0069] Comparative Example 1

[0070] The raw material "modified glass fiber obtained in Example 3" used in Example 6 was replaced with unmodified conventional glass fiber, and a nucleating agent was added by conventional blending.

[0071] A foamed PET sheet comprises the following raw materials in parts by weight: 100 parts polyethylene terephthalate, 7 parts F-260D microspheres, 0.28 parts antioxidant 626, 0.17 parts zinc oxide, 1.2 parts stearic acid, 25 parts glass fiber, and 1 part nucleating agent DMDBS;

[0072] A method for preparing foamed PET sheets includes the following steps:

[0073] Step 1: Weigh each raw material according to the specified mass fractions;

[0074] Step 2: Add polyethylene terephthalate, glass fiber, antioxidant 626, zinc oxide, stearic acid, F-260D microspheres, and nucleating agent DMDBS to a mixer and mix thoroughly to obtain a homogeneous mixture for later use.

[0075] The third step involves melting and extruding the homogeneous mixture using a twin-screw extruder at a temperature of 170-180℃. After cooling, traction, and granulation, the mixture is then injection molded to obtain foamed PET sheets.

[0076] Experiment Example 2

[0077] The foamed PET sheets obtained in Examples 4-6 and Comparative Example 1 were subjected to performance tests. Bending performance was tested according to GB / T 9341-2008 "Determination of Bending Properties of Plastics", impact resistance was tested according to GB / T 1843-2008 "Determination of Cantilever Beam Impact Strength of Plastics", and tensile performance was tested according to GB / T 1040.2-2006 "Determination of Tensile Properties of Plastics". The average pore size of each component sample was measured using an optical microscope. The test results are shown in Table 1.

[0078] Table 1

[0079] project Bending strength Impact resistance Tensile strength Average aperture Example 4 29.32MPa 2.32MPa 23.17MPa 13.32μm Example 5 31.46MPa 2.44MPa 24.68MPa 14.43μm Example 6 32.03MPa 2.86MPa 25.14MPa 14.86μm Comparative Example 1 24.63MPa 1.12MPa 20.37MPa 46.47μm

[0080] As can be seen from Table 1, compared with conventional blending methods, the foamed PET sheets obtained by the preparation method of the present invention in Examples 4-6 have a significant improvement in impact resistance. The reason is that the conventional blending method results in uneven dispersion. The average pore size of the foamed PET sheet in Comparative Example 1 is much larger than that of the foamed PET sheet obtained by the preparation method of the present invention, and local stress concentration points are created inside, which leads to a decrease in bending strength and tensile strength, and significantly affects the impact resistance of the material.

[0081] The above provides a detailed description of a foamed PET sheet and its preparation method provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combination method. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the invention. In particular, as long as there is no structural conflict, the features in the embodiments disclosed in the present invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A foamed PET sheet, characterized in that, It contains the following raw materials: polyethylene terephthalate, foaming agent, antioxidant, zinc oxide, lubricant, and modified glass fiber; The modified glass fiber is prepared by the following steps: Step 1: Using anhydrous ethanol as a solvent, graft the silane coupling agent KH-560 onto glass fibers to obtain epoxidized glass fibers; Step 2: Under nitrogen protection, sorbitol, 4-methyl-3-nitrobenzaldehyde, p-toluenesulfonic acid, and cyclohexane are mixed evenly and the reaction temperature is controlled at 55-80℃ to obtain the nucleating agent. Step 3: Then, using ethanol solution as a solvent, sodium sulfide is used to reduce the nucleating agent to obtain an amination nucleating agent; Step 4: Finally, anhydrous ethanol is used as a solvent to graft the amination nucleating agent onto the surface of the epoxide glass fiber to obtain modified glass fiber. In step 2, the ratio of sorbitol, 4-methyl-3-nitrobenzaldehyde, p-toluenesulfonic acid, and cyclohexane used by mass is 1.3-1.5 parts: 2.3-2.7 parts: 0.02-0.05 parts: 50-120 parts.

2. The foamed PET sheet according to claim 1, characterized in that, The ratio of silane coupling agent KH-560, glass fiber, and anhydrous ethanol used in step 1, by mass parts, is 2-4 parts: 5-10 parts: 180-240 parts.

3. The foamed PET sheet according to claim 1, characterized in that, The ethanol solution used in step 3 is an aqueous ethanol solution with a volume fraction of 10-20%. By mass, the ratio of nucleating agent, ethanol solution and sodium sulfide used in step 3 is 2.5-3 parts: 40-100 parts: 1.8-2.4 parts.

4. The foamed PET sheet according to claim 1, characterized in that, The ratio of amination nucleating agent, epoxidized glass fiber, and anhydrous ethanol used in step 4, by mass parts, is 1-2 parts: 5-10 parts: 180-240 parts.

5. A foamed PET sheet according to claim 1, characterized in that, The antioxidant is one of antioxidant 1076, antioxidant 1010, and antioxidant 626.

6. The foamed PET sheet according to claim 1, characterized in that, The foaming agent is one of F-230D microspheres and F-260D microspheres.

7. A foamed PET sheet according to claim 1, characterized in that, The lubricant is stearic acid.

8. A method for preparing a foamed PET sheet according to any one of claims 1-7, characterized in that, Includes the following steps: After weighing each raw material according to the specified mass fraction, the raw materials are blended and extruded, and after cooling, traction, and granulation processes, they are injection molded to obtain short glass fiber reinforced polyethylene terephthalate foam material.

9. The method for preparing a foamed PET sheet according to claim 8, characterized in that, The mass percentages of each raw material are as follows: 100 parts polyethylene terephthalate, 4-7 parts foaming agent, 0.14-0.28 parts antioxidant, 0.06-0.17 parts zinc oxide, 0.4-1.2 parts lubricant, and 15-25 parts modified glass fiber.

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