Impact-resistant high-transparency cast polyurethane material and preparation method thereof

Abstract

The application discloses an anti-impact high-transparency casting polyurethane material and a preparation method thereof, relates to the technical field of polyurethane, and aims to improve the transparency and cold-heat impact resistance of the casting polyurethane. The preparation method comprises the following steps: S1: under a nitrogen atmosphere, 50-65 parts of polyether polyol are dehydrated at 100-120 DEG C, then cooled to 60-65 DEG C, 25-35 parts of isocyanate are added, and stirring reaction is carried out at 90-95 DEG C for 3-5 hours to obtain a casting polyurethane A component; S2: 8-12 parts of a chain extender, 2-4 parts of modified silica aerogel and 0.1-0.5 parts of a defoaming agent are uniformly mixed to obtain a casting polyurethane B component; S3: the casting polyurethane A component and the casting polyurethane B component are uniformly mixed after being preheated respectively to obtain a casting liquid; the casting liquid is poured into a mold, the mold is closed, pressure is kept, and vulcanization treatment is carried out, so that the anti-impact high-transparency casting polyurethane material is obtained.

Description

Technical Field

[0001] This invention relates to the field of polyurethane technology, specifically to the C08G classification, and more specifically to an impact-resistant, high-transmittance castable polyurethane material and its preparation method. Background Technology

[0002] Cast polyurethane elastomers possess excellent mechanical properties and impact resistance, and are commonly used in protective applications such as sports protective gear and equipment protection. With industrial upgrading, these protective materials not only need to maintain reliable performance in extreme environments such as extreme cold and heat, but also need to have good light transmittance to meet monitoring needs such as visualization. Silica aerogel has a low thermal conductivity, and its introduction can increase the operating temperature range of materials; however, it is highly prone to aggregation, and its introduction can easily form light scattering centers, thus deteriorating light transmittance.

[0003] In summary, solving the above problems and preparing an impact-resistant, high-transmittance castable polyurethane material and its preparation method is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide an impact-resistant, high-transmittance castable polyurethane material and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing an impact-resistant, high-transmittance castable polyurethane material includes the following steps: S1: Under a nitrogen atmosphere, 50-65 parts by mass of polyether polyol are dehydrated at 100-120°C, then cooled to 60-65°C, and 25-35 parts by mass of isocyanate are added. The mixture is stirred and reacted at 90-95°C for 3-5 hours to obtain casting polyurethane component A. S2: Mix 8-12 parts of chain extender, 2-4 parts of modified silica aerogel, and 0.1-0.5 parts of defoamer evenly by weight to obtain component B of castable polyurethane; S3: Preheat the casting polyurethane component A and casting polyurethane component B separately and mix them evenly to obtain a casting liquid; pour it into a mold, close the mold, hold pressure, and vulcanize to obtain an impact-resistant and high-transmittance casting polyurethane material. The chain extender includes trimethylolpropane, a fluorinated chain extender, and 1,2-octanediol in a mass ratio of 1:2 to 3:3 to 4.

[0006] Preferably, the mass ratio of the cast polyurethane component A to the cast polyurethane component B is 100:10~20.

[0007] Preferredly, the preparation method of the fluorinated chain extender includes the following steps: under a nitrogen atmosphere, hexafluorobutanol is added to a solvent and mixed evenly, isophorone diisocyanate and dibutyltin dilaurate are added sequentially, and the mixture is stirred at 80~90℃ for 2~3h, cooled to 0~5℃, diethanolamine is added, and the mixture is stirred for another 20~30min. The solvent is removed by rotary evaporation to obtain the fluorinated chain extender.

[0008] By controlling the reaction temperature to 80-90℃ and the reaction time to 2-3h, and by adding diethanolamine at a low temperature of 0-5℃, the side reaction between the hydroxyl group and the isocyanate group in diethanolamine can be effectively suppressed.

[0009] Preferably, the fluorinated chain extender comprises the following raw materials in parts by mass: 8-12 parts hexafluorobutanol, 9.8-14.7 parts isophorone diisocyanate, 0.01-0.05 parts dibutyltin dilaurate, and 4.6-6.9 parts diethanolamine.

[0010] Preferred method for preparing modified silica aerogel includes the following steps: (1) Under a nitrogen atmosphere, glycidyl methacrylate, methoxy polyethylene glycol methacrylate and benzoyl peroxide are added to dioxane and mixed evenly. The mixture is stirred and reacted at 80-85°C for 2-2.5 hours. After freezing, it is diluted and concentrated with dichloromethane and washed with n-hexane to obtain epoxy flexible copolymer. (2) Add urea-formaldehyde modified silica aerogel to tetrahydrofuran and disperse evenly. Add epoxy flexible copolymer and stir at 70~80℃ for 30~40 min. Add benzyltrimethylammonium chloride and add perfluorohexylethyl mercaptan. Continue stirring for 20~30 min. Centrifuge, wash and dry to obtain modified silica aerogel.

[0011] Preferably, the epoxy flexible copolymer comprises the following raw materials, in parts by weight: 5-6 parts glycidyl methacrylate, 10-12 parts methoxy polyethylene glycol methacrylate, and 0.1-0.3 parts benzoyl peroxide; The modified silica aerogel comprises the following raw materials, by mass parts: 10-15 parts urea-formaldehyde modified silica aerogel, 8-12 parts epoxy flexible copolymer, 1-3 parts benzyltrimethylammonium chloride, and 7-8 parts perfluorohexylethyl mercaptan. The urea-formaldehyde modified silica aerogel was obtained by in-situ coating modification with urea-formaldehyde resin.

[0012] Preferably, the polyether polyol is polytetrahydrofuran ether diol with a molecular weight of 1000-2000; and the isocyanate is isophorone diisocyanate.

[0013] Preferably, the temperature during the preheating process is 80~90℃; and the temperature during the vulcanization process is 90~100℃, and the time is 12~24h.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention uses a compound of fluorinated chain extender, trimethylolpropane, and 1,2-octanediol as chain extender, and adds silica aerogel grafted with epoxy flexible copolymer and fluorinated to prepare a castable polyurethane material that significantly improves flexibility and has a certain degree of resistance to thermal shock while ensuring high light transmittance.

[0015] The preparation process of the fluorinated chain extender involves introducing a fluorocarbon chain through the reaction of the hydroxyl groups of hexafluorobutanol with the isocyanate groups of isophorone diisocyanate, followed by end-capping with the secondary amino groups of diethanolamine to obtain a fluorinated chain extender with terminal hydroxyl groups. The introduction of fluorinated groups can improve the hydrophobicity and low-temperature resistance of polyurethane materials. Simultaneously, its steric hindrance can reduce the regularity of hard segments, decrease the crystallinity of hard segments, and improve light transmittance. However, due to the significant polarity difference between the fluorinated component and the polyurethane matrix, the compatibility after introduction is poor, easily leading to excessive microphase separation and consequently a decrease in light transmittance. This application introduces a chain extender prepared with fluorinated groups into the chain ends, achieving a good modification effect with a relatively small dosage. Furthermore, this application uses a specific ratio of trimethylolpropane as a crosslinking chain extender, 1,2-octanediol as a small molecule diol chain extender, and the fluorinated chain extender synergistically regulate the hard segment structure and improve light transmittance.

[0016] The preparation process of the modified silica aerogel is as follows: silica aerogel is first subjected to in-situ polycondensation of urea and formaldehyde to form urea-formaldehyde modified silica aerogel; further, glycidyl methacrylate and methoxy polyethylene glycol methacrylate are copolymerized to prepare an epoxy flexible copolymer, and its epoxy groups are used to graft and modify the surface of the urea-formaldehyde modified silica aerogel, and further fluorination treatment is introduced with perfluorohexyl ethyl mercaptan to obtain a modified silica aerogel with fluorinated flexible copolymer on the surface. Silica aerogel has extremely high nanoscale porosity, thus exhibiting good thermal barrier properties and improving the thermal shock resistance of polyurethane materials. After urea-formaldehyde coating, the surface contains active sites that can react with the polyurethane system, improving the interfacial bonding with the polyurethane matrix. However, urea-formaldehyde resin itself is brittle and has a significant difference in modulus between its soft segment and that of polyurethane, leading to stress concentration at the interface and reduced thermal shock resistance. Furthermore, its compatibility with the fluorinated polyurethane matrix prepared in this application remains insufficient, and uneven dispersion results in decreased transparency. Therefore, this invention further improves interfacial toughness through surface grafting treatment of flexible copolymers, buffering interfacial stress during thermal shock and thus improving thermal shock resistance. In addition, further fluorination treatment helps improve the compatibility between the modified aerogel and the fluorinated polyurethane matrix, thereby improving light transmittance while ensuring thermal shock resistance. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the following examples, parts are by weight; the particle size of the silica aerogel is 40 nm, and the specific surface area is 230 m². 2 / g; CAS number of hexafluorobutanol: 382-31-0; molecular weight of methoxy polyethylene glycol methacrylate (mPEGMA): 300; CAS number of perfluorohexyl ethyl mercaptan: 34143-74-3; polyether polyol: polytetrahydrofuran ether diol, molecular weight: 1000; isocyanate: isophorone diisocyanate; defoamer: YRXP-05; all other raw materials are commercially available.

[0019] In the following examples, the preparation method of urea-formaldehyde modified silica aerogel includes the following steps: 12 parts of silica aerogel are added to ethanol and ultrasonically dispersed evenly; 22 parts of 30wt% urea aqueous solution are added; the mixture is stirred and reacted for 1~1.5h; the pH is adjusted to 1±0.1 with hydrochloric acid; 6.5 parts of formaldehyde are added; the mixture is stirred and reacted at 90℃ for 6h; the mixture is centrifuged, washed, and dried to obtain urea-formaldehyde modified silica aerogel.

[0020] Example 1: A method for preparing an impact-resistant, high-transmittance castable polyurethane material includes the following steps: Step 1: Preparation of fluorinated chain extender: Under a nitrogen atmosphere, 8 parts of hexafluorobutanol were added to ethyl acetate and mixed evenly. Then, 9.8 parts of isophorone diisocyanate and 0.02 parts of dibutyltin dilaurate were added sequentially and stirred at 80°C for 2 hours. The mixture was then cooled to 1°C, and 4.6 parts of diethanolamine were added. The mixture was stirred for another 25 minutes, and the solvent was removed by rotary evaporation to obtain the fluorinated chain extender. Step 2: Preparation of modified silica aerogel: (1) Under a nitrogen atmosphere, 5.5 parts glycidyl methacrylate, 11 parts methoxy polyethylene glycol methacrylate, and 0.2 parts benzoyl peroxide were added to dioxane and mixed evenly. The mixture was stirred at 80°C for 2 hours. After freezing, it was diluted and concentrated with dichloromethane and washed with n-hexane to obtain epoxy flexible copolymer; (2) 15 parts urea-formaldehyde modified silica aerogel were added to tetrahydrofuran and dispersed evenly. 12 parts epoxy flexible copolymer were added and stirred at 75°C for 35 minutes. 3 parts benzyltrimethylammonium chloride were added and 8 parts perfluorohexylethyl mercaptan were added dropwise. The mixture was stirred and reacted for another 25 minutes. After centrifugation, washing, and drying, modified silica aerogel was obtained. Step 3: Preparation of impact-resistant, high-transmittance castable polyurethane material: S1: Under a nitrogen atmosphere, 59 parts of polyether polyol were dehydrated at 110°C, then cooled to 60°C, and 29.5 parts of isocyanate were added. The mixture was stirred at 90°C for 4 hours to obtain casting polyurethane component A. S2: Weigh out trimethylolpropane, fluorinated chain extender, and 1,2-octanediol in a mass ratio of 1:2.5:3.5 as chain extenders; mix 12 parts of chain extender, 3 parts of modified silica aerogel, and 0.2 parts of defoamer evenly to obtain casting polyurethane component B; S3: Preheat the casting polyurethane component A and casting polyurethane component B to 80°C respectively, mix them evenly at a mass ratio of 100:17 to obtain the casting liquid; pour it into a mold preheated to 100°C, close the mold, hold pressure, and vulcanize at 95°C for 20 hours to obtain an impact-resistant, high-transparency casting polyurethane material.

[0021] Example 2: A method for preparing an impact-resistant, high-transmittance castable polyurethane material includes the following steps: Step 1: Preparation of fluorinated chain extender: Under a nitrogen atmosphere, 8 parts of hexafluorobutanol were added to ethyl acetate and mixed evenly. Then, 9.8 parts of isophorone diisocyanate and 0.02 parts of dibutyltin dilaurate were added sequentially and stirred at 80°C for 2 hours. The mixture was then cooled to 1°C, and 4.6 parts of diethanolamine were added. The mixture was stirred for another 25 minutes, and the solvent was removed by rotary evaporation to obtain the fluorinated chain extender. Step 2: Preparation of modified silica aerogel: (1) Under a nitrogen atmosphere, 5.5 parts glycidyl methacrylate, 11 parts methoxy polyethylene glycol methacrylate, and 0.2 parts benzoyl peroxide were added to dioxane and mixed evenly. The mixture was stirred at 80°C for 2 hours. After freezing, it was diluted and concentrated with dichloromethane and washed with n-hexane to obtain epoxy flexible copolymer; (2) 15 parts urea-formaldehyde modified silica aerogel were added to tetrahydrofuran and dispersed evenly. 12 parts epoxy flexible copolymer were added and stirred at 75°C for 35 minutes. 3 parts benzyltrimethylammonium chloride were added and 8 parts perfluorohexylethyl mercaptan were added dropwise. The mixture was stirred and reacted for another 25 minutes. After centrifugation, washing, and drying, modified silica aerogel was obtained. Step 3: Preparation of impact-resistant, high-transmittance castable polyurethane material: S1: Under a nitrogen atmosphere, 64.5 parts of polyether polyol were dehydrated at 110°C, then cooled to 60°C, and 27 parts of isocyanate were added. The mixture was stirred at 90°C for 4 hours to obtain casting polyurethane component A. S2: Weigh out trimethylolpropane, fluorinated chain extender, and 1,2-octanediol in a mass ratio of 1:2:4 as chain extenders; mix 9 parts of chain extender, 2 parts of modified silica aerogel, and 0.2 parts of defoamer evenly to obtain casting polyurethane component B; S3: Preheat the casting polyurethane component A and casting polyurethane component B to 80°C respectively, mix them evenly at a mass ratio of 100:12 to obtain the casting liquid; pour it into a mold preheated to 100°C, close the mold, hold pressure, and vulcanize at 95°C for 20 hours to obtain an impact-resistant, high-transparency casting polyurethane material.

[0022] Example 3: A method for preparing an impact-resistant, high-transmittance castable polyurethane material includes the following steps: Step 1: Preparation of fluorinated chain extender: Under a nitrogen atmosphere, 8 parts of hexafluorobutanol were added to ethyl acetate and mixed evenly. Then, 9.8 parts of isophorone diisocyanate and 0.02 parts of dibutyltin dilaurate were added sequentially and stirred at 80°C for 2 hours. The mixture was then cooled to 1°C, and 4.6 parts of diethanolamine were added. The mixture was stirred for another 25 minutes, and the solvent was removed by rotary evaporation to obtain the fluorinated chain extender. Step 2: Preparation of modified silica aerogel: (1) Under a nitrogen atmosphere, 5.5 parts glycidyl methacrylate, 11 parts methoxy polyethylene glycol methacrylate, and 0.2 parts benzoyl peroxide were added to dioxane and mixed evenly. The mixture was stirred at 80°C for 2 hours. After freezing, it was diluted and concentrated with dichloromethane and washed with n-hexane to obtain epoxy flexible copolymer; (2) 15 parts urea-formaldehyde modified silica aerogel were added to tetrahydrofuran and dispersed evenly. 12 parts epoxy flexible copolymer were added and stirred at 75°C for 35 minutes. 3 parts benzyltrimethylammonium chloride were added and 8 parts perfluorohexylethyl mercaptan were added dropwise. The mixture was stirred and reacted for another 25 minutes. After centrifugation, washing, and drying, modified silica aerogel was obtained. Step 3: Preparation of impact-resistant, high-transmittance castable polyurethane material: S1: Under a nitrogen atmosphere, 65 parts of polyether polyol were dehydrated at 110°C, then cooled to 60°C, and 30.5 parts of isocyanate were added. The mixture was stirred and reacted at 90°C for 4 hours to obtain casting polyurethane component A. S2: Weigh out trimethylolpropane, fluorinated chain extender, and 1,2-octanediol in a mass ratio of 1:3:3 as chain extenders; mix 12 parts of chain extender, 4 parts of modified silica aerogel, and 0.2 parts of defoamer evenly to obtain casting polyurethane component B; S3: Preheat the casting polyurethane component A and casting polyurethane component B to 80°C respectively, mix them evenly at a mass ratio of 100:17 to obtain the casting liquid; pour it into a mold preheated to 100°C, close the mold, hold pressure, and vulcanize at 95°C for 20 hours to obtain an impact-resistant, high-transparency casting polyurethane material.

[0023] Comparative Example 1: Compared to Example 1, no fluorine-containing modifier was introduced. The specific process is as follows: Step 1: Preparation of modified silica aerogel: (1) Under a nitrogen atmosphere, 5.5 parts glycidyl methacrylate, 11 parts methoxy polyethylene glycol methacrylate and 0.2 parts benzoyl peroxide were added to dioxane and mixed evenly. The mixture was stirred at 80°C for 2 hours. After freezing, it was diluted and concentrated with dichloromethane and washed with n-hexane to obtain epoxy flexible copolymer; (2) 15 parts urea-formaldehyde modified silica aerogel were added to tetrahydrofuran and dispersed evenly. 12 parts epoxy flexible copolymer were added and stirred at 75°C for 35 minutes. 3 parts benzyltrimethylammonium chloride were added and 8 parts perfluorohexylethyl mercaptan were added dropwise. The mixture was stirred and reacted for another 25 minutes. After centrifugation, washing and drying, modified silica aerogel was obtained. Step Two: Preparation of Impact-Resistant, High-Transmittance Castable Polyurethane Material: S1: Under a nitrogen atmosphere, 59 parts of polyether polyol were dehydrated at 110°C, then cooled to 60°C, and 29.5 parts of isocyanate were added. The mixture was stirred at 90°C for 4 hours to obtain casting polyurethane component A. S2: Weigh trimethylolpropane and 1,2-octanediol in a mass ratio of 1:6 as chain extenders; mix 12 parts of chain extender, 3 parts of modified silica aerogel, and 0.2 parts of defoamer evenly to obtain casting polyurethane component B; S3: Preheat the casting polyurethane component A and casting polyurethane component B to 80°C respectively, mix them evenly at a mass ratio of 100:17 to obtain the casting liquid; pour it into a mold preheated to 100°C, close the mold, hold pressure, and vulcanize at 95°C for 20 hours to obtain an impact-resistant, high-transparency casting polyurethane material.

[0024] Comparative Example 2: Compared to Example 1, the mass ratio of the chain extender was adjusted, and the specific process is shown below: Step 1: Preparation of fluorinated chain extender: Under a nitrogen atmosphere, 8 parts of hexafluorobutanol were added to ethyl acetate and mixed evenly. Then, 9.8 parts of isophorone diisocyanate and 0.02 parts of dibutyltin dilaurate were added sequentially and stirred at 80°C for 2 hours. The mixture was then cooled to 1°C, and 4.6 parts of diethanolamine were added. The mixture was stirred for another 25 minutes, and the solvent was removed by rotary evaporation to obtain the fluorinated chain extender. Step 2: Preparation of modified silica aerogel: (1) Under a nitrogen atmosphere, 5.5 parts glycidyl methacrylate, 11 parts methoxy polyethylene glycol methacrylate, and 0.2 parts benzoyl peroxide were added to dioxane and mixed evenly. The mixture was stirred at 80°C for 2 hours. After freezing, it was diluted and concentrated with dichloromethane and washed with n-hexane to obtain epoxy flexible copolymer; (2) 15 parts urea-formaldehyde modified silica aerogel were added to tetrahydrofuran and dispersed evenly. 12 parts epoxy flexible copolymer were added and stirred at 75°C for 35 minutes. 3 parts benzyltrimethylammonium chloride were added and 8 parts perfluorohexylethyl mercaptan were added dropwise. The mixture was stirred and reacted for another 25 minutes. After centrifugation, washing, and drying, modified silica aerogel was obtained. Step 3: Preparation of impact-resistant, high-transmittance castable polyurethane material: S1: Under a nitrogen atmosphere, 59 parts of polyether polyol were dehydrated at 110°C, then cooled to 60°C, and 29.5 parts of isocyanate were added. The mixture was stirred at 90°C for 4 hours to obtain casting polyurethane component A. S2: Weigh out trimethylolpropane, fluorinated chain extender, and 1,2-octanediol in a mass ratio of 1:1:5 as chain extenders; mix 12 parts of chain extender, 3 parts of modified silica aerogel, and 0.2 parts of defoamer evenly to obtain casting polyurethane component B. S3: Preheat the casting polyurethane component A and casting polyurethane component B to 80°C respectively, mix them evenly at a mass ratio of 100:17 to obtain the casting liquid; pour it into a mold preheated to 100°C, close the mold, hold pressure, and vulcanize at 95°C for 20 hours to obtain an impact-resistant, high-transparency casting polyurethane material.

[0025] Comparative Example 3: Compared to Example 1, the silica aerogel only used urea-formaldehyde modification, and the specific process is shown below: Step 1: Preparation of fluorinated chain extender: Under a nitrogen atmosphere, 8 parts of hexafluorobutanol were added to ethyl acetate and mixed evenly. Then, 9.8 parts of isophorone diisocyanate and 0.02 parts of dibutyltin dilaurate were added sequentially and stirred at 80°C for 2 hours. The mixture was then cooled to 1°C, and 4.6 parts of diethanolamine were added. The mixture was stirred for another 25 minutes, and the solvent was removed by rotary evaporation to obtain the fluorinated chain extender. Step Two: Preparation of Impact-Resistant, High-Transmittance Castable Polyurethane Material: S1: Under a nitrogen atmosphere, 59 parts of polyether polyol were dehydrated at 110°C, then cooled to 60°C, and 29.5 parts of isocyanate were added. The mixture was stirred at 90°C for 4 hours to obtain casting polyurethane component A. S2: Weigh out trimethylolpropane, fluorinated chain extender, and 1,2-octanediol in a mass ratio of 1:2.5:3.5 as chain extenders; mix 12 parts of chain extender, 3 parts of urea-formaldehyde modified silica aerogel, and 0.2 parts of defoamer evenly to obtain casting polyurethane component B; S3: Preheat the casting polyurethane component A and casting polyurethane component B to 80°C respectively, mix them evenly at a mass ratio of 100:17 to obtain the casting liquid; pour it into a mold preheated to 100°C, close the mold, hold pressure, and vulcanize at 95°C for 20 hours to obtain an impact-resistant, high-transparency casting polyurethane material.

[0026] Comparative Example 4: Compared to Example 1, the silica aerogel modification process did not involve further fluorination treatment. The specific process is as follows: Step 1: Preparation of fluorinated chain extender: Under a nitrogen atmosphere, 8 parts of hexafluorobutanol were added to ethyl acetate and mixed evenly. Then, 9.8 parts of isophorone diisocyanate and 0.02 parts of dibutyltin dilaurate were added sequentially and stirred at 80°C for 2 hours. The mixture was then cooled to 1°C, and 4.6 parts of diethanolamine were added. The mixture was stirred for another 25 minutes, and the solvent was removed by rotary evaporation to obtain the fluorinated chain extender. Step 2: Preparation of modified silica aerogel: (1) Under a nitrogen atmosphere, 5.5 parts of glycidyl methacrylate, 11 parts of methoxy polyethylene glycol methacrylate and 0.2 parts of benzoyl peroxide were added to dioxane and mixed evenly. The mixture was stirred at 80°C for 2 hours. After freezing, it was diluted and concentrated with dichloromethane and washed with hexane to obtain epoxy flexible copolymer; (2) 15 parts of urea-formaldehyde modified silica aerogel were added to tetrahydrofuran and dispersed evenly. 12 parts of epoxy flexible copolymer were added and stirred at 75°C for 35 minutes. 3 parts of benzyltrimethylammonium chloride were added and stirred for another 25 minutes. The mixture was centrifuged, washed and dried to obtain modified silica aerogel; Step 3: Preparation of impact-resistant, high-transmittance castable polyurethane material: S1: Under a nitrogen atmosphere, 59 parts of polyether polyol were dehydrated at 110°C, then cooled to 60°C, and 29.5 parts of isocyanate were added. The mixture was stirred at 90°C for 4 hours to obtain casting polyurethane component A. S2: Weigh out trimethylolpropane, fluorinated chain extender, and 1,2-octanediol in a mass ratio of 1:2.5:3.5 as chain extenders; mix 12 parts of chain extender, 3 parts of modified silica aerogel, and 0.2 parts of defoamer evenly to obtain casting polyurethane component B; S3: Preheat the casting polyurethane component A and casting polyurethane component B to 80°C respectively, mix them evenly at a mass ratio of 100:17 to obtain the casting liquid; pour it into a mold preheated to 100°C, close the mold, hold pressure, and vulcanize at 95°C for 20 hours to obtain an impact-resistant, high-transparency casting polyurethane material.

[0027] Performance testing: (1) Tear strength was tested according to GB / T 529; right-angled specimens were used and the tensile rate was 500 mm / min; (2) The elongation at break and tensile strength were tested according to GB / T 528 standard, with type 1 dumbbell-shaped specimens and a tensile rate of 500 mm / min. (3) After subjecting the samples to thermal cycling shock according to GB / T 2423.22, the tensile strength was measured again and the tensile strength retention rate was calculated; the low temperature was -65℃, the high temperature was 125℃, the duration of high and low temperature exposure was 2h each, and the number of cycles was 20. (4) The light transmittance of the sample was measured using a haze meter in accordance with GB / T 2410; the sample thickness was 2 mm. Conclusions: Comparative Example 1, without the introduction of a fluorinated modifier, exhibits improved hard segment regularity, leading to the formation of crystalline regions, reduced elongation, and exacerbated low-temperature embrittlement. The retention rate after thermal shock is significantly reduced, and the lack of compatibility with fluorinated aerogels results in a significant decrease in light transmittance. Comparative Example 2, by adjusting the mass ratio of chain extenders and reducing the amount of fluorinated chain extenders, decreases the ability to control microphase separation, leading to a decline in overall performance. Comparative Example 3, using only urea-formaldehyde modification for silica aerogels, suffers from high brittleness and stress concentration at the interface, resulting in decreased tear strength and elongation at break, and significantly reduced performance under thermal shock, along with a certain decrease in light transmittance. Comparative Example 4, without further fluorination during silica aerogel modification, exhibits insufficient compatibility, leading to a decrease in light transmittance and tensile strength retention. However, due to the grafting of a flexible copolymer, the elongation at break is significantly improved compared to Comparative Example 3. Therefore, the polyurethane casting material prepared in this application exhibits good light transmittance and excellent thermal shock resistance.

[0028] It will be apparent to those skilled in the art that the present invention is not limited to the specific details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit and core features of the invention. Therefore, the above embodiments should be considered exemplary rather than restrictive in any respect. The scope of protection of the present invention is defined by the appended claims, not by the foregoing description, and is therefore intended to encompass all variations in the meaning and scope of the equivalents of the claims within the scope of the present invention.

Claims

1. A method for preparing an impact-resistant, high-transmittance castable polyurethane material, characterized in that: Includes the following steps: S1: Under a nitrogen atmosphere, 50-65 parts by mass of polyether polyol are dehydrated at 100-120°C, then cooled to 60-65°C, and 25-35 parts by mass of isocyanate are added. The mixture is stirred and reacted at 90-95°C for 3-5 hours to obtain casting polyurethane component A. S2: Mix 8-12 parts of chain extender, 2-4 parts of modified silica aerogel, and 0.1-0.5 parts of defoamer evenly by weight to obtain component B of castable polyurethane; S3: Preheat the casting polyurethane component A and casting polyurethane component B separately and mix them evenly to obtain a casting liquid; pour it into a mold, close the mold, hold pressure, and vulcanize to obtain an impact-resistant and high-transmittance casting polyurethane material. The chain extender includes trimethylolpropane, a fluorinated chain extender, and 1,2-octanediol in a mass ratio of 1:2 to 3:3 to 4.

2. The method for preparing an impact-resistant, high-transmittance castable polyurethane material according to claim 1, characterized in that: The mass ratio of cast polyurethane component A to cast polyurethane component B is 100:10~20.

3. The method for preparing an impact-resistant, high-transmittance castable polyurethane material according to claim 1, characterized in that: The preparation method of the fluorinated chain extender includes the following steps: under a nitrogen atmosphere, hexafluorobutanol is added to a solvent and mixed evenly, isophorone diisocyanate and dibutyltin dilaurate are added sequentially, and the mixture is stirred at 80~90℃ for 2~3h, cooled to 0~5℃, diethanolamine is added, and the mixture is stirred for another 20~30min. The solvent is removed by rotary evaporation to obtain the fluorinated chain extender.

4. The method for preparing an impact-resistant, high-transmittance castable polyurethane material according to claim 3, characterized in that: The fluorinated chain extender comprises the following raw materials, in parts by mass: 8-12 parts hexafluorobutanol, 9.8-14.7 parts isophorone diisocyanate, 0.01-0.05 parts dibutyltin dilaurate, and 4.6-6.9 parts diethanolamine.

5. The method for preparing an impact-resistant, high-transmittance castable polyurethane material according to claim 1, characterized in that: The preparation method of the modified silica aerogel includes the following steps: (1) Under a nitrogen atmosphere, glycidyl methacrylate, methoxy polyethylene glycol methacrylate and benzoyl peroxide are added to dioxane and mixed evenly. The mixture is stirred and reacted at 80~85℃ for 2~2.5h. After freezing, it is diluted and concentrated with dichloromethane, and washed with n-hexane to obtain an epoxy flexible copolymer. (2) Add urea-formaldehyde modified silica aerogel to tetrahydrofuran and disperse evenly. Add epoxy flexible copolymer and stir at 70~80℃ for 30~40 min. Add benzyltrimethylammonium chloride and add perfluorohexylethyl mercaptan. Continue stirring for 20~30 min. Centrifuge, wash and dry to obtain modified silica aerogel.

6. The method for preparing an impact-resistant, high-transmittance castable polyurethane material according to claim 5, characterized in that: The epoxy flexible copolymer comprises the following raw materials, in parts by weight: 5-6 parts glycidyl methacrylate, 10-12 parts methoxy polyethylene glycol methacrylate, and 0.1-0.3 parts benzoyl peroxide; The modified silica aerogel comprises the following raw materials, by mass parts: 10-15 parts urea-formaldehyde modified silica aerogel, 8-12 parts epoxy flexible copolymer, 1-3 parts benzyltrimethylammonium chloride, and 7-8 parts perfluorohexylethyl mercaptan. The urea-formaldehyde modified silica aerogel was obtained by in-situ coating modification with urea-formaldehyde resin.

7. The method for preparing an impact-resistant, high-transmittance castable polyurethane material according to claim 1, characterized in that: The polyether polyol is polytetrahydrofuran ether diol with a molecular weight of 1000-2000; the isocyanate is isophorone diisocyanate.

8. The method for preparing an impact-resistant, high-transmittance castable polyurethane material according to claim 1, characterized in that: During the preheating process, the temperature is 80~90℃; during the vulcanization process, the temperature is 90~100℃ and the time is 12~24h.

9. The castable polyurethane material prepared by the method for preparing an impact-resistant, high-transmittance castable polyurethane material according to any one of claims 1 to 8.

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