A calcium sulfate whisker reinforced plastic sheet and its preparation process

Abstract

The present invention relates to the technical field of polymer compounds and discloses a calcium sulfate whisker reinforced plastic sheet and its preparation process. Preparation process: S1: Take p-aminophenol, octadecanal, and anhydrous ethanol, stir at 60-70°C for 3-6 hours, remove the solvent, wash, and dry to obtain a Schiff base; take the Schiff base, DOPO, and anhydrous ethanol, stir at 60-70°C for 4-6 hours, cool, filter, wash, and dry to obtain modified DOPO; take the modified DOPO, tetraethylene glycol diglycidyl ether, bisphenol F diglycidyl ether, and dimethylformamide, heat and stir uniformly, raise the temperature to 110-130°C, stir for 4-6 hours, remove the solvent, and obtain a flame retardant; S2: Mix and stir epoxy resin, calcium sulfate whisker filler, and flame retardant, add a curing agent, stir and mix uniformly, vacuum degas, and place in a mold for curing to obtain a plastic sheet.

Description

Technical Field

[0001] The invention relates to the technical field of polymer compounds and discloses a calcium sulfate whisker reinforced plastic plate and a preparation process thereof. Background Art

[0002] Plastic sheets are widely used in many fields such as construction, chemical industry, electronics, and automobiles. Epoxy resin is a high-performance thermosetting polymer. After curing, epoxy resin has the advantages of high strength, good corrosion resistance, and good wear resistance. It can be used in the manufacture of plastic sheets.

[0003] Fillers are often introduced to further improve the performance of epoxy resin plastic sheets. Calcium sulfate whiskers are fibrous, whisker-like single crystals made from gypsum. They possess advantages such as high strength, high toughness, and high-temperature resistance, making them suitable for resin fillers. However, the introduction of calcium sulfate whiskers as fillers cannot completely improve the inherently poor toughness and flame retardancy of epoxy resins. Furthermore, calcium sulfate whiskers have poor compatibility in the resin matrix, and uneven dispersion can lead to a decrease in the performance of the plastic sheet. Therefore, it is of great significance to develop a calcium sulfate whisker-reinforced plastic sheet with excellent strength, toughness, and flame retardancy, as well as a preparation process. Summary of the Invention

[0004] The object of the present invention is to provide a calcium sulfate whisker reinforced plastic sheet and a preparation process thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: A preparation process for a calcium sulfate whisker reinforced plastic sheet, comprising the following steps: S1: taking p-aminophenol, octadecanal, and anhydrous ethanol, stirring at 60-70°C for 3-6 hours, cooling, filtering, washing, and drying to obtain a Schiff base; taking a Schiff base, DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), and anhydrous ethanol, stirring at 60-70°C for 4-6 hours, cooling, filtering, washing, and drying to obtain a modified DOPO; taking the modified DOPO, tetraethylene glycol diglycidyl ether, bisphenol F diglycidyl ether, and dimethylformamide, heating and stirring uniformly, raising the temperature to 110-130°C and stirring for 4-6 hours, and removing the solvent to obtain a flame retardant;

[0006] S2: Mix epoxy resin, calcium sulfate whisker filler, and flame retardant, add curing agent, stir and mix thoroughly, vacuum degas, place in a mold for curing, and obtain a plastic sheet.

[0007] More optimally, the Schiff base includes the following raw materials, calculated in parts by mass: 10-12 parts of p-aminophenol, 25-30 parts of octadecanal, and 300-350 parts of anhydrous ethanol; the modified DOPO includes the following raw materials, calculated in parts by mass: 10-15 parts of Schiff base, 5-8 parts of DOPO, and 300-350 parts of anhydrous ethanol; the flame retardant includes the following raw materials, calculated in parts by mass: 20-25 parts of modified DOPO, 5-10 parts of tetraethylene glycol diglycidyl ether, 10-15 parts of bisphenol F diglycidyl ether, and 300-400 parts of dimethylformamide.

[0008] More optimally, the plastic sheet comprises the following raw materials, calculated by mass: 100-150 parts of epoxy resin, 50-60 parts of calcium sulfate whisker filler, 20-30 parts of flame retardant, and 8-10 parts of curing agent.

[0009] More optimally, the preparation method of the calcium sulfate whisker filler includes the following steps: taking calcium sulfate whiskers, an amino-containing silane coupling agent (3-aminopropyltriethoxysilane), anhydrous ethanol, and water, mixing them evenly, adjusting the pH value to 8-10, heating to 40-50°C and stirring to react for 3-5 hours, filtering, and drying the solid to obtain the calcium sulfate whisker filler.

[0010] More optimally, the calcium sulfate whisker filler includes the following raw materials, calculated by mass: 10 to 15 parts of calcium sulfate whiskers, 1 to 3 parts of amino-containing silane coupling agent, 100 to 150 parts of anhydrous ethanol, and 50 to 60 parts of water.

[0011] More optimally, the curing agent is a small molecule curing agent.

[0012] More optimally, the curing agent is m-xylenediamine.

[0013] More optimally, the curing conditions are: curing at 70-80°C for 3-4 hours, and curing at 110-130°C for 1-2 hours.

[0014] More optimally, the preparation of the calcium sulfate whiskers includes the following steps: taking calcium sulfate dihydrate, crushing it to obtain small pieces with a particle size of 5 to 15 cm, and soaking it in a potion for 12 to 15 hours; in the potion, the mass ratio of acetic acid, glycerol, penetrant JFC, calcium lignin sulfonate, and water is (8 to 10): (5 to 6): (1 to 2): (1 to 2): (90 to 100); placing the soaked small pieces in a steaming kettle, raising the temperature to 150 to 160° C. and the pressure to 0.5 to 0.6 MPa, and maintaining the temperature and pressure for 10 to 12 hours to obtain hemihydrate gypsum; at 60 to 65° C., using a double-roll mill to perform primary crushing of the hemihydrate gypsum into strips and flocs, grinding, air separation, drying, cooling, and homogenization to obtain calcium sulfate whiskers.

[0015] More optimally, the diameter of the calcium sulfate whiskers is 1 to 4 μm and the length is 50 to 150 μm.

[0016] Compared with the prior art, the present invention achieves the following beneficial effects: a flame retardant is added, wherein the flame retardant first reacts with p-aminophenol and octadecanal to obtain a Schiff base, which then undergoes an addition reaction with DOPO to obtain modified DOPO; wherein the long alkyl chain of octadecanal is a flexible segment that can enhance the toughness of the epoxy resin; under the reaction conditions of the present invention, the -OH group in p-aminophenol is retained and participates in the next reaction;

[0017] The introduction of a large amount of calcium sulfate whiskers as fillers reduces the fluidity of the epoxy resin, making processing difficult and performance unstable. Therefore, reactive diluents tetraethylene glycol diglycidyl ether and bisphenol F diglycidyl ether are introduced, and the reaction between epoxy groups and hydroxyl groups in modified DOPO is used to produce a flame retardant with diluent properties. The tetraethylene glycol diglycidyl ether and bisphenol F diglycidyl ether not only serve as diluents but also improve the compatibility of the modified DOPO with the epoxy resin matrix. The flexible chain segments of tetraethylene glycol diglycidyl ether can improve the toughness of the epoxy resin, and bisphenol F diglycidyl ether can improve the heat resistance and strength of the epoxy resin. The addition amount of both needs to be controlled to produce epoxy resin plastic sheets with good toughness, high strength and good flame retardancy.

[0018] Due to the introduction of diluent, the curing rate is slow. Therefore, the calcium sulfate whiskers are modified with amino-containing silane coupling agents to improve the compatibility of calcium sulfate whiskers in epoxy resin on the one hand, and to assist curing and improve curing efficiency on the other hand. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0020] It should be noted that the purchase manufacturers of all raw materials involved in the present invention are not subject to any special restrictions, and illustratively include: epoxy resin (E51, Wuhan Jushun Chemical Co., Ltd. js2024121009); calcium sulfate dihydrate (99%, Hubei Shishun Biotechnology Co., Ltd. SS0605); acetic acid (food grade); glycerol (pharmaceutical grade); penetrant JFC (Jiyesheng A00450); calcium lignin sulfonate (Yuanye S50911); amino-containing silane coupling agent (3-aminopropyltriethoxysilane, CAS: 919-30-2); p-Aminophenol (CAS: 123-30-8); Octadecanal (stearyl aldehyde, CAS: 638-66-4); DOPO (Source Leaf S46419, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, CAS: 35948-25-5); Tetraethylene glycol diglycidyl ether (CAS: 17626-93-6); Bisphenol F diglycidyl ether (CAS: 2095-03-6); Dimethylformamide (CAS: 68-12-2);

[0021] Unless otherwise specified, the following are parts by mass and mass ratios;

[0022] Example 1: S1: Calcium sulfate dihydrate was crushed to obtain small pieces with a particle size of 10 cm, and the pieces were soaked in a solution with a composition of acetic acid: glycerol: penetrant JFC: calcium lignin sulfonate: water = 10:5:1:1:90 for 14 hours; the soaked small pieces were placed in an autoclave, the temperature was raised to 150° C. and the pressure was raised to 0.6 MPa within 1 hour, and the temperature and pressure were maintained for 10 hours to obtain hemihydrate gypsum; the hemihydrate gypsum was primarily crushed into flocculent strips using a double-roll mill at 60° C., and the material was ground using a mill at 110° C., air-selected, dried, cooled, and homogenized to obtain calcium sulfate whiskers;

[0023] S2: Take 10 parts of calcium sulfate whiskers, 1.5 parts of amino-containing silane coupling agent, 100 parts of anhydrous ethanol, and 50 parts of water, mix them evenly, adjust the pH value to 9, heat to 50°C and stir to react for 5 hours, filter, and dry the solid to obtain calcium sulfate whisker filler;

[0024] S3: Take 10 parts of p-aminophenol, 28 parts of octadecanal, and 300 parts of anhydrous ethanol, stir at 60°C for 5 hours, cool, filter, wash, and dry to obtain a Schiff base; take 12 parts of Schiff base, 7 parts of DOPO, and 300 parts of anhydrous ethanol, stir at 60°C for 6 hours, cool, filter, wash, and dry to obtain a modified DOPO; take 24 parts of modified DOPO, 6 parts of tetraethylene glycol diglycidyl ether, 12 parts of bisphenol F diglycidyl ether, and 400 parts of dimethylformamide, heat to 100°C and stir evenly, then heat to 120°C and stir for 5 hours, remove the solvent, and obtain a flame retardant;

[0025] S4: 100 parts of epoxy resin, 55 parts of calcium sulfate whisker filler, and 25 parts of flame retardant were mixed and stirred, and 10 parts of m-xylenediamine were added and stirred and mixed. 4 Pa) and stirred, degassed for 12 minutes, and placed in a molding mold for curing at 70° C. for 4 hours and at 120° C. for 1 hour to obtain a plastic sheet.

[0026] Example 2: S1: Calcium sulfate dihydrate was crushed to obtain small pieces with a particle size of 10 cm, and the pieces were soaked in a solution with a composition of acetic acid: glycerol: penetrant JFC: calcium lignin sulfonate: water = 10:5:1:1:90 for 14 hours; the soaked small pieces were placed in an autoclave, the temperature was raised to 150° C. and the pressure was raised to 0.6 MPa within 1 hour, and the temperature and pressure were maintained for 10 hours to obtain hemihydrate gypsum; the hemihydrate gypsum was primarily crushed into flocculent strips using a double-roll mill at 60° C., and the material was ground using a mill at 110° C., air-selected, dried, cooled, and homogenized to obtain calcium sulfate whiskers;

[0027] S2: Take 10 parts of calcium sulfate whiskers, 1.5 parts of amino-containing silane coupling agent, 100 parts of anhydrous ethanol, and 50 parts of water, mix them evenly, adjust the pH value to 9, heat to 50°C and stir to react for 5 hours, filter, and dry the solid to obtain calcium sulfate whisker filler;

[0028] S3: Take 10 parts of p-aminophenol, 25 parts of octadecanal, and 300 parts of anhydrous ethanol, stir at 60°C for 5 hours, cool, filter, wash, and dry to obtain a Schiff base; take 10 parts of Schiff base, 5 parts of DOPO, and 300 parts of anhydrous ethanol, stir at 60°C for 6 hours, cool, filter, wash, and dry to obtain a modified DOPO; take 20 parts of modified DOPO, 5 parts of tetraethylene glycol diglycidyl ether, 10 parts of bisphenol F diglycidyl ether, and 400 parts of dimethylformamide, heat to 100°C and stir evenly, then heat to 120°C and stir for 5 hours, remove the solvent, and obtain a flame retardant;

[0029] S4: 100 parts of epoxy resin, 55 parts of calcium sulfate whisker filler, and 25 parts of flame retardant were mixed and stirred, and 10 parts of m-xylenediamine were added and stirred and mixed. 4 Pa) and stirred, degassed for 12 minutes, and placed in a molding mold for curing at 80° C. for 3 hours and at 115° C. for 2 hours to obtain a plastic sheet.

[0030] Example 3: S1: Calcium sulfate dihydrate was crushed to obtain small pieces with a particle size of 10 cm, and the pieces were soaked in a solution with a composition of acetic acid: glycerol: penetrant JFC: calcium lignin sulfonate: water = 10:5:1:1:90 for 14 hours; the soaked small pieces were placed in an autoclave, the temperature was raised to 150° C. and the pressure was raised to 0.6 MPa within 1 hour, and the temperature and pressure were maintained for 10 hours to obtain hemihydrate gypsum; the hemihydrate gypsum was primarily crushed into flocculent strips using a double-roll mill at 60° C., and the material was ground using a mill at 110° C., air-selected, dried, cooled, and homogenized to obtain calcium sulfate whiskers;

[0031] S2: Take 10 parts of calcium sulfate whiskers, 1.5 parts of amino-containing silane coupling agent, 100 parts of anhydrous ethanol, and 50 parts of water, mix them evenly, adjust the pH value to 9, heat to 50°C and stir to react for 5 hours, filter, and dry the solid to obtain calcium sulfate whisker filler;

[0032] S3: Take 12 parts of p-aminophenol, 30 parts of octadecanal, and 300 parts of anhydrous ethanol, stir at 60°C for 5 hours, cool, filter, wash, and dry to obtain a Schiff base; take 15 parts of Schiff base, 8 parts of DOPO, and 300 parts of anhydrous ethanol, stir at 60°C for 6 hours, cool, filter, wash, and dry to obtain a modified DOPO; take 25 parts of modified DOPO, 10 parts of tetraethylene glycol diglycidyl ether, 15 parts of bisphenol F diglycidyl ether, and 400 parts of dimethylformamide, heat to 100°C and stir evenly, then heat to 120°C and stir for 5 hours, remove the solvent, and obtain a flame retardant;

[0033] S4: 100 parts of epoxy resin, 55 parts of calcium sulfate whisker filler, and 25 parts of flame retardant were mixed and stirred, and 10 parts of m-xylenediamine were added and stirred and mixed. 4 Pa) and stirred, degassed for 12 minutes, and placed in a molding mold for curing at 70° C. for 3 hours and at 120° C. for 2 hours to obtain a plastic sheet.

[0034] Comparative Example 1 (the preparation method of the flame retardant was changed, and the remaining steps were consistent with Example 1): S1: Calcium sulfate dihydrate was taken, crushed to obtain small pieces with a particle size of 10 cm, and soaked in a potion for 14 hours, wherein the composition of the potion was acetic acid: glycerol: penetrant JFC: calcium lignin sulfonate: water = 10:5:1:1:90; the soaked small pieces were placed in a steam curing kettle, the temperature was increased to 150° C. and the pressure was increased to 0.6 MPa within 1 hour, and the heat and pressure were maintained for 10 hours to obtain hemihydrate gypsum; at 60° C., the hemihydrate gypsum was primarily crushed into strips using a double-roll mill, and the material was ground using a mill at 110° C., air-selected, dried, cooled, and homogenized to obtain calcium sulfate whiskers;

[0035] S2: Take 10 parts of calcium sulfate whiskers, 1.5 parts of amino-containing silane coupling agent, 100 parts of anhydrous ethanol, and 50 parts of water, mix them evenly, adjust the pH value to 9, heat to 50°C and stir to react for 5 hours, filter, and dry the solid to obtain calcium sulfate whisker filler;

[0036] S3: Take 5 parts of p-aminophenol and 14 parts of octadecanal, mix them to obtain mixture A; take 12 parts of mixture A and 7 parts of DOPO, mix them to obtain mixture B; take 4 parts of mixture B, 1 part of tetraethylene glycol diglycidyl ether, and 2 parts of bisphenol F diglycidyl ether, mix them to obtain a flame retardant;

[0037] S4: 100 parts of epoxy resin, 55 parts of calcium sulfate whisker filler, and 25 parts of flame retardant were mixed and stirred, and 10 parts of m-xylenediamine were added and stirred and mixed. 4 Pa) and stirred, degassed for 12 minutes, and placed in a molding mold for curing at 70° C. for 4 hours and at 120° C. for 1 hour to obtain a plastic sheet.

[0038] Comparative Example 2 (the addition ratio of tetraethylene glycol diglycidyl ether and bisphenol F diglycidyl ether was changed, and the remaining method steps were consistent with Example 1): S1: Calcium sulfate dihydrate was taken, crushed to obtain small pieces with a particle size of 10 cm, and placed in a potion soaked for 14 hours, wherein the composition of the potion was acetic acid: glycerol: penetrant JFC: calcium lignin sulfonate: water = 10:5:1:1:90; the soaked small pieces were placed in an autoclave, the temperature was increased to 150° C. and the pressure was increased to 0.6 MPa within 1 hour, and the heat and pressure were maintained for 10 hours to obtain hemihydrate gypsum; at 60° C., the hemihydrate gypsum was primarily crushed into strips using a double-roll mill, ground using a grinder at 110° C., air-selected, dried, cooled, and homogenized to obtain calcium sulfate whiskers;

[0039] S2: Take 10 parts of calcium sulfate whiskers, 1.5 parts of amino-containing silane coupling agent, 100 parts of anhydrous ethanol, and 50 parts of water, mix them evenly, adjust the pH value to 9, heat to 50°C and stir to react for 5 hours, filter, and dry the solid to obtain calcium sulfate whisker filler;

[0040] S3: Take 10 parts of p-aminophenol, 28 parts of octadecanal, and 300 parts of anhydrous ethanol, stir at 60°C for 5 hours, cool, filter, wash, and dry to obtain a Schiff base; take 12 parts of Schiff base, 7 parts of DOPO, and 300 parts of anhydrous ethanol, stir at 60°C for 6 hours, cool, filter, wash, and dry to obtain a modified DOPO; take 24 parts of modified DOPO, 12 parts of tetraethylene glycol diglycidyl ether, 6 parts of bisphenol F diglycidyl ether, and 400 parts of dimethylformamide, heat to 100°C and stir evenly, then heat to 120°C and stir for 5 hours, remove the solvent, and obtain a flame retardant;

[0041] S4: 100 parts of epoxy resin, 55 parts of calcium sulfate whisker filler, and 25 parts of flame retardant were mixed and stirred, and 10 parts of m-xylenediamine were added and stirred and mixed. 4 Pa) and stirred, degassed for 12 minutes, and placed in a molding mold for curing at 70° C. for 4 hours and at 120° C. for 1 hour to obtain a plastic sheet.

[0042] Comparative Example 3 (the addition ratio of tetraethylene glycol diglycidyl ether and bisphenol F diglycidyl ether was changed, and the remaining method steps were consistent with Example 1): S1: Calcium sulfate dihydrate was taken, crushed to obtain small pieces with a particle size of 10 cm, and soaked in a potion for 14 hours, wherein the composition of the potion was acetic acid: glycerol: penetrant JFC: calcium lignin sulfonate: water = 10:5:1:1:90; the soaked small pieces were placed in an autoclave, the temperature was increased to 150° C. and the pressure was increased to 0.6 MPa within 1 hour, and the heat and pressure were maintained for 10 hours to obtain hemihydrate gypsum; at 60° C., the hemihydrate gypsum was primarily crushed into strips using a double-roll mill, and ground using a grinder at 110° C., air-selected, dried, cooled, and homogenized to obtain calcium sulfate whiskers;

[0043] S2: Take 10 parts of calcium sulfate whiskers, 1.5 parts of amino-containing silane coupling agent, 100 parts of anhydrous ethanol, and 50 parts of water, mix them evenly, adjust the pH value to 9, heat to 50°C and stir to react for 5 hours, filter, and dry the solid to obtain calcium sulfate whisker filler;

[0044] S3: Take 10 parts of p-aminophenol, 28 parts of octadecanal, and 300 parts of anhydrous ethanol, stir at 60°C for 5 hours, cool, filter, wash, and dry to obtain a Schiff base; take 12 parts of Schiff base, 7 parts of DOPO, and 300 parts of anhydrous ethanol, stir at 60°C for 6 hours, cool, filter, wash, and dry to obtain a modified DOPO; take 24 parts of modified DOPO, 2 parts of tetraethylene glycol diglycidyl ether, 17 parts of bisphenol F diglycidyl ether, and 400 parts of dimethylformamide, heat to 100°C and stir evenly, then heat to 120°C and stir for 5 hours, remove the solvent, and obtain a flame retardant;

[0045] S4: 100 parts of epoxy resin, 55 parts of calcium sulfate whisker filler, and 25 parts of flame retardant were mixed and stirred, and 10 parts of m-xylenediamine were added and stirred and mixed. 4 Pa) and stirred, degassed for 12 minutes, and placed in a molding mold for curing at 70° C. for 4 hours and at 120° C. for 1 hour to obtain a plastic sheet.

[0046] Comparative Example 4 (the preparation method of the flame retardant was changed, and the remaining steps were consistent with Example 1): S1: Calcium sulfate dihydrate was taken, crushed to obtain small pieces with a particle size of 10 cm, and soaked in a potion for 14 hours, wherein the composition of the potion was acetic acid: glycerol: penetrant JFC: calcium lignin sulfonate: water = 10:5:1:1:90; the soaked small pieces were placed in a steam curing kettle, the temperature was increased to 150°C and the pressure was increased to 0.6 MPa within 1 hour, and the heat and pressure were maintained for 10 hours to obtain hemihydrate gypsum; at 60°C, the hemihydrate gypsum was primarily crushed into flocculent strips using a double-roll mill, ground using a mill at 110°C, air-selected, dried, cooled, and homogenized to obtain calcium sulfate whiskers;

[0047] S2: Take 10 parts of calcium sulfate whiskers, 1.5 parts of amino-containing silane coupling agent, 100 parts of anhydrous ethanol, and 50 parts of water, mix them evenly, adjust the pH value to 9, heat to 50°C and stir to react for 5 hours, filter, and dry the solid to obtain calcium sulfate whisker filler;

[0048] S3: Take 10 parts of p-aminophenol, 28 parts of octadecanal, and 300 parts of anhydrous ethanol, stir at 60°C for 5 hours, cool, filter, wash, and dry to obtain a Schiff base; take 12 parts of Schiff base, 7 parts of DOPO, and 300 parts of anhydrous ethanol, stir at 60°C for 6 hours, cool, filter, wash, and dry to obtain a modified DOPO; take 24 parts of modified DOPO, 6 parts of tetraethylene glycol diglycidyl ether, and 12 parts of bisphenol F diglycidyl ether, mix well to obtain a flame retardant;

[0049] S4: 100 parts of epoxy resin, 55 parts of calcium sulfate whisker filler, and 25 parts of flame retardant were mixed and stirred, and 10 parts of m-xylenediamine were added and stirred and mixed. 4 Pa) and stirred, degassed for 12 minutes, and placed in a molding mold for curing at 70° C. for 4 hours and at 120° C. for 1 hour to obtain a plastic sheet.

[0050] Performance test: The plastic sheets prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were processed into strips and tested for tensile strength, notched impact strength, and oxygen index; see Table 1 for details.

[0051] Table 1:

[0052]

[0053] Conclusion: Comparative Example 1 changes the preparation method of the flame retardant, and simply mixes p-aminophenol, octadecanal, DOPO, tetraethylene glycol diglycidyl ether, and bisphenol F diglycidyl ether to obtain a flame retardant. Due to compatibility and other problems, the performance is significantly reduced; Comparative Examples 2 and 3 change the addition ratio of tetraethylene glycol diglycidyl ether and bisphenol F diglycidyl ether, and the performance is not as good as the embodiment. It can be seen that controlling the ratio of the two is of great significance; Comparative Example 4 also changes the preparation method of the flame retardant, and tetraethylene glycol diglycidyl ether and bisphenol F diglycidyl ether are not grafted onto the modified DOPO, resulting in reduced compatibility of the modified DOPO and a decrease in overall performance; In summary, the plastic sheet prepared by the present invention has good strength, toughness and flame retardancy.

[0054] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A process for preparing a calcium sulfate whisker reinforced plastic sheet, characterized in that: The following steps are involved: S1: Take p-aminophenol, octadecanal, and anhydrous ethanol, stir at 60-70°C for 3-6 hours, cool, filter, wash, and dry to obtain a Schiff base; take a Schiff base, DOPO, and anhydrous ethanol, stir at 60-70°C for 4-6 hours, cool, filter, wash, and dry to obtain modified DOPO; Take modified DOPO, tetraethylene glycol diglycidyl ether, bisphenol F diglycidyl ether, and dimethylformamide, heat and stir evenly, raise the temperature to 110-130°C, stir for 4-6 hours, and remove the solvent to obtain a flame retardant; S2: Mixing epoxy resin, calcium sulfate whisker filler, and flame retardant, adding curing agent, stirring and mixing, vacuum degassing, and placing in a mold for curing to obtain a plastic sheet; The Schiff base comprises the following raw materials, calculated by weight: 10-12 parts of p-aminophenol, 25-30 parts of octadecanal, and 300-350 parts of anhydrous ethanol; The modified DOPO comprises the following raw materials, calculated by weight: 10-15 parts of Schiff base, 5-8 parts of DOPO, and 300-350 parts of anhydrous ethanol; the flame retardant comprises the following raw materials, calculated by weight: 20-25 parts of modified DOPO, 5-10 parts of tetraethylene glycol diglycidyl ether, 10-15 parts of bisphenol F diglycidyl ether, and 300-400 parts of dimethylformamide; The plastic sheet comprises the following raw materials, calculated by mass: 100-150 parts of epoxy resin, 50-60 parts of calcium sulfate whisker filler, 20-30 parts of flame retardant, and 8-10 parts of curing agent.

2. The process for preparing a calcium sulfate whisker reinforced plastic sheet according to claim 1, wherein: The preparation method of the calcium sulfate whisker filler comprises the following steps: taking calcium sulfate whiskers, an amino-containing silane coupling agent, anhydrous ethanol, and water, mixing them uniformly, adjusting the pH value to 8-10, heating to 40-50° C., stirring and reacting for 3-5 hours, filtering, and drying the solid to obtain the calcium sulfate whisker filler.

3. The process for preparing a calcium sulfate whisker reinforced plastic sheet according to claim 2, wherein: The calcium sulfate whisker filler comprises the following raw materials, calculated by mass: 10-15 parts of calcium sulfate whiskers, 1-3 parts of amino-containing silane coupling agents, 100-150 parts of anhydrous ethanol, and 50-60 parts of water.

4. The process for preparing a calcium sulfate whisker reinforced plastic sheet according to claim 1, wherein: The curing agent is a small molecule curing agent.

5. The process for preparing a calcium sulfate whisker reinforced plastic sheet according to claim 1, wherein: The curing conditions are: curing at 70-80° C. for 3-4 hours and curing at 110-130° C. for 1-2 hours.

6. The process for preparing a calcium sulfate whisker reinforced plastic sheet according to claim 1, wherein: The preparation of the calcium sulfate whisker comprises the following steps: Calcium sulfate dihydrate is crushed to obtain small pieces with a particle size of 5-15 cm, and the small pieces are soaked in a potion for 12-15 hours; the mass ratio of acetic acid, glycerol, penetrant, calcium lignin sulfonate, and water in the potion is (8-10):(5-6):(1-2):(1-2):(90-100); the soaked small pieces are placed in a steam curing kettle, the temperature is raised to 150-160° C., the pressure is increased to 0.5-0.6 MPa, and the temperature and pressure are maintained for 10-12 hours to obtain hemihydrate gypsum; the hemihydrate gypsum is primarily crushed into strips and flocs using a double-roll mill at 60-65° C., and the mixture is ground, air-selected, dried, cooled, and homogenized to obtain calcium sulfate whiskers.

7. A plastic sheet prepared according to the process for preparing a calcium sulfate whisker reinforced plastic sheet according to any one of claims 1 to 6.

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