High-strength high-tear polyurethane sponge and preparation method thereof

Abstract

The application relates to the technical field of polyurethane sponge materials, in particular to a high-strength and high-tear polyurethane sponge and a preparation method thereof. A high-strength and high-tear polyurethane sponge is prepared from the following raw materials in parts by weight: 35-60 parts of diisocyanate, 40-75 parts of polyhydric alcohol, 2-4.5 parts of a functionalized chain extender, 2.5-6.5 parts of a dynamic crosslinking agent, 1.5-4.0 parts of a foaming agent, 0.1-0.5 parts of a catalyst and 0.8-1.6 parts of a foam stabilizer; the functionalized chain extender is polyoxyethylene diamine with a weight average molecular weight of 500-1000 and N-aminoethylpiperazine; the R value of the high-strength and high-tear polyurethane sponge is 1.0-1.25; and the mass ratio of the polyoxyethylene diamine with a molecular weight of 500-1000 to the N-aminoethylpiperazine is (1.5-5):1. The polyurethane sponge prepared in the application has excellent tensile resistance and tear resistance.

Description

Technical Field

[0001] This invention relates to the field of polyurethane foam materials technology, and in particular to a high-strength, high-tear-resistance polyurethane foam and its preparation method. Background Technology

[0002] Polyurethane foam, also known as polyurethane flexible foam, has excellent properties such as low density, good elasticity, breathability, sound absorption, cushioning, and resilience, making it widely used in furniture and mattresses, vehicle seating systems, packaging and cushioning materials, sound insulation and sound absorption materials, clothing and daily consumer goods, sports and protective equipment, and other fields.

[0003] Existing polyurethane foams are synthesized using polypropylene glycol PPG-2000 and polyether polyol POP36 / 28 as polyols and foaming agents. The tensile strength of the synthesized polyurethane foam is 100-150 kPa, and the tear strength is 2.0-3.0 N / cm. Its tensile and tear resistance are poor and cannot meet the market demand. Therefore, the inventor provides a high-strength and high-tear polyurethane foam and its preparation method. Summary of the Invention

[0004] To address the issue of discrepancies in the tensile and tear resistance properties of polyurethane foams in existing technologies, this invention provides a high-strength, high-tear-resistance polyurethane foam and its preparation method.

[0005] The high-strength, high-tear-resistance polyurethane foam provided by this invention is achieved through the following technical solution: A high-strength, high-tear-resistance polyurethane foam is made from the following raw materials in parts by weight: 35-60 parts diisocyanate, 40-75 parts polyol, 2-4.5 parts functionalized chain extender, 2.5-6.5 parts dynamic crosslinking agent, 1.5-4.0 parts foaming agent, 0.1-0.5 parts catalyst, 0.8-1.6 parts foam stabilizer, and 0.05-0.20 parts antioxidant; wherein the functionalized chain extender is polyoxyethylene diamine and N-aminoethylpiperazine with a molecular weight of 500-1000; and the R-value of the high-strength, high-tear-resistance polyurethane foam is 1.0-1.25.

[0006] Preferably, the mass ratio of the polyoxyethylene diamine with a molecular weight of 500-1000 to N-aminoethylpiperazine is (1.5-5):1.

[0007] Preferably, the polyol is polypropylene glycol and polytetrahydrofuran ether glycol with a molecular weight of 1500-3000.

[0008] More preferably, the polyol is polypropylene glycol and polytetrahydrofuran ether glycol with a molecular weight of 1500-3000.

[0009] In this invention, polyoxyethylene diamine, N-aminoethylpiperazine and dynamic crosslinking agent are used in synergy to improve the tensile strength and tear resistance of polyurethane foam, while ensuring that the prepared polyurethane foam still maintains good resilience (resilience rate ≥35%) and resistance to compression set (≤8%).

[0010] Preferably, the dynamic crosslinking agent is a polyether-type polyurethane prepolymer A with an NCO content of 3-5% and a polyether-type polyurethane prepolymer B with an NCO content of 3-5%, wherein the polyether-type polyurethane prepolymer A contains furan groups and the polyether-type polyurethane prepolymer B contains maleimide groups.

[0011] During the curing stage of polyurethane foam, the furan groups in polyether-type polyurethane prepolymer A and the maleimide groups in polyether-type polyurethane prepolymer B form DA bonds, which improves the crosslinking density of polyurethane foam and thus improves tensile strength, tear resistance, resilience and compression set resistance.

[0012] Preferably, the catalyst is catalyst A-1 or catalyst A-33.

[0013] Preferably, the foam stabilizer is an organosilicon foam stabilizer.

[0014] More preferably, the silicone foam stabilizer includes at least L-580.

[0015] Preferably, the foaming agent is water.

[0016] Preferably, the diisocyanate is at least one of MDI, TDI, and carbodiimide-modified MDI.

[0017] The polyurethane foam in this invention has a tensile strength ≥200 Kpa, tear strength ≥6.0 N / cm, elongation at break ≥250%, air permeability 1000-1500 mm / s, compression set ≤8.0%, and resilience ≥35%. It has good tensile and tear resistance, as well as good resilience and resistance to compression set.

[0018] Preferably, the polyol is polypropylene glycol, polytetrahydrofuran ether glycol, or an organophosphorus halide reactive flame retardant with a molecular weight of 1500-3000.

[0019] More preferably, the organophosphorus halide reactive flame retardant is at least one of FR-300, FRT-4, WSFR-780, WSFR-780LS, and V68.

[0020] By adopting the above technical solutions, polyurethane foam can be guaranteed to have excellent tensile strength, tear resistance, resilience, and resistance to compression set, while also having good flame retardant safety performance.

[0021] The present invention provides a method for preparing a high-strength, high-tear-resistance polyurethane foam, which is achieved through the following technical solution: A method for preparing a high-strength, high-tear-resistance polyurethane foam includes the following steps: Step 1: Measure the polyols according to the formula, mix them evenly, and then add the functionalized chain extender, foaming agent, catalyst, foam stabilizer, and antioxidant and mix evenly to obtain a mixture. Step 2: Add diisocyanate and dynamic crosslinking agent to the mixture and mix evenly to obtain rigid polyurethane foam resin; Step 3: Pour the foam into a mold at room temperature and let it foam until the foam interface is stable. Adjust the temperature to 60-80℃ and cure for 24-36 hours. Demolding will then yield high-strength, high-tear-resistance polyurethane foam.

[0022] The preparation method of the high-strength, high-tear-resistance polyurethane foam provided in this application is relatively simple, widely applicable, and has relatively low operational requirements, making it easy to achieve industrialized production.

[0023] In summary, the present invention has the following advantages: the present invention uses polyoxyethylene diamine, N-aminoethylpiperazine and dynamic crosslinking agent in synergy to improve the tensile strength (tensile strength ≥200 Kpa, elongation at break ≥250%) and tear resistance (tear strength ≥6.0 N / cm) of polyurethane foam, while also ensuring that the prepared polyurethane foam still maintains good resilience (resilience ≥35%) and resistance to compression set (≤8%). Detailed Implementation

[0024] To further understand the inventiveness and technical advancements of this invention, the preferred embodiments of this invention will be discussed in detail below with reference to examples and comparative examples.

[0025] Example: A high-strength, high-tear-resistance polyurethane foam is made of 35-60 parts of diisocyanate, 40-75 parts of polyol, 2-4.5 parts of functionalized chain extender, 2.5-6.5 parts of dynamic crosslinking agent, 1.5-4.0 parts of foaming agent, 0.1-0.5 parts of catalyst, 0.8-1.6 parts of foam stabilizer, and 0.05-0.20 parts of antioxidant.

[0026] The R value in high-strength, high-tear-resistance polyurethane foam is 1.0-1.25.

[0027] The diisocyanate is at least one of MDI, TDI, and carbodiimide-modified MDI.

[0028] The polyol is polypropylene glycol and polytetrahydrofuran ether glycol with a molecular weight of 1500-3000. Preferably, the polyol is polypropylene glycol and polytetrahydrofuran ether glycol with a hydroxyl value of 50-65 mg KOH / g.

[0029] The molar ratio of polypropylene glycol to polytetrahydrofuran ether glycol is (1.8-2.5):1, preferably (2.2-2.3):1.

[0030] The catalysts are catalyst A-1 and catalyst A-33.

[0031] Preferably, the mass ratio of catalyst A-1 to catalyst A-33 is 1:1.

[0032] The foam stabilizer is an organosilicon foam stabilizer, and the organosilicon foam stabilizer includes at least L-580.

[0033] The foaming agent is water.

[0034] The functionalized chain extender is polyoxyethylene diamine and N-aminoethylpiperazine with a molecular weight of 500-1000. Preferably, the functionalized chain extender is polyoxyethylene diamine and N-aminoethylpiperazine with a molecular weight of 600. The mass ratio of polyoxyethylene diamine to N-aminoethylpiperazine is (1.5-5):1.

[0035] The dynamic crosslinking agent is a polyether-type polyurethane prepolymer A with an NCO content of 3-5% and a polyether-type polyurethane prepolymer B with an NCO content of 3-5%. The polyether-type polyurethane prepolymer A contains furan groups, and the polyether-type polyurethane prepolymer B contains maleimide groups.

[0036] The antioxidant is at least one of antioxidant 1010, antioxidant 1098, antioxidant 168, and antioxidant BHT. Preferably, the antioxidant is a compound of antioxidant 1010 and antioxidant 168.

[0037] To improve the flame retardancy of polyurethane foam, organophosphorus halide reactive flame retardants can be incorporated into the polyol, specifically at least one of FR-300, FRT-4, WSFR-780, WSFR-780LS, and V68.

[0038] A method for preparing a high-strength, high-tear-resistance polyurethane foam includes the following steps: Step 1: Measure the polyols according to the formula, mix them evenly, and then add the functionalized chain extender, foaming agent, catalyst, foam stabilizer, and antioxidant and mix evenly to obtain a mixture. Step 2: Add diisocyanate and dynamic crosslinking agent to the mixture and mix evenly to obtain rigid polyurethane foam resin; Step 3: Pour the foam into a mold at room temperature and let it foam until the foam interface is stable. Adjust the temperature to 60-80℃ and cure for 24-36 hours. Demolding will then yield high-strength, high-tear-resistance polyurethane foam.

[0039] Preparation Example 1: A method for synthesizing a dynamic crosslinking agent-polyether type polyurethane prepolymer, comprising the following steps: S1. Synthesis of polyether-type polyurethane prepolymer A: Under nitrogen protection, 0.2 mol (34.84 g) of TDI-80 (Bluestar Chemical Co., Ltd.) and 100 g of DMF were mixed evenly, and then 0.1 mol (12.82 g) of 2,5-furandimethylethanol (Shanghai Maclean Biochemical Technology Co., Ltd.) and 0.02 g of bismuth isooctanoate (Shanghai Maclean Biochemical Technology Co., Ltd.) were added. The temperature was adjusted to 75℃ and the reaction was carried out for 2 h. The -NCO content in the system was measured until the -NCO content reached the theoretical value. Then, 120 g of polytetrahydrofuran ether PTMEG-600 (BASF PolyTHF) was added. The mixture was reacted at 75℃ for 2 hours, and the -NCO content in the system was measured until the -NCO content was 0. Then, 0.2 mol (34.84 g) of TDI-80 was added, and the mixture was capped at 75℃ for 2 hours. DMF was removed by vacuum distillation to obtain polyether-type polyurethane prepolymer A, which had a -NCO content of 4.14%. S2. Synthesis of polyether-type polyurethane prepolymer B: Under nitrogen protection, 0.1 mol (9.20 g) amino-1,3-propanediol (Shanghai Yuanye Biotechnology Co., Ltd.) and 100 g DMF were mixed evenly, and then 0.1 mol (21.42 g) 4-(maleimide)phenyl isocyanate (Shanghai Maclean Biochemical Technology Co., Ltd.) was added. The temperature was adjusted to 45℃ and the reaction was carried out for 2 h. The -NCO content in the system was measured until the -NCO content was 0. Then, 0.2 mol (34.84 g) TDI-80 was added, and the temperature was adjusted to 75℃ and the reaction was carried out for 2 h. The -NCO content in the system was measured until the -NCO content reached the theoretical value. Then, 120 g of polytetrahydrofuran ether PTMEG-600 (BASF PolyTHF) was added. The mixture was reacted at 75℃ for 2 hours, and the -NCO content in the system was measured until the -NCO content was 0. Then, 0.2 mol (34.84 g) of TDI-80 was added, and the mixture was capped at 75℃ for 2 hours. DMF was removed by vacuum distillation to obtain polyether-type polyurethane prepolymer B, which had an -NCO content of 3.66%. S3. Weigh 2.35 parts by weight of polyether-type polyurethane prepolymer A and 2.65 parts by weight of polyether-type polyurethane prepolymer B, and mix them at 300 rpm for 8 minutes at room temperature to obtain the finished dynamic crosslinking agent.

[0040] Example 1: A high-strength, high-tear-resistance polyurethane foam is made from the following raw materials: 35 parts by weight of TDI-80 / 20 (TDI-80, Bluestar Chemical Co., Ltd.), 36 parts by weight of polypropylene glycol PPG-2000 (Shanghai KBT Chemical Co., Ltd.), 16 parts by weight of polytetrahydrofuran ether PTMEG-2000 (BASF PolyTHF 2000), 2.25 parts by weight of polyoxyethylene diamine (weight average molecular weight Mw=600, CAS:24991-53-5, Shanghai Aladdin Biochemical Technology Co., Ltd.), 0.75 parts by weight of N-aminoethylpiperazine (Shanghai Aladdin Biochemical Technology Co., Ltd.), 3 parts by weight of deionized water, 5 parts by weight of the dynamic crosslinking agent in Preparation Example 1 - polyether-type polyurethane prepolymer (2.35 parts by weight of polyether-type polyurethane prepolymer A + 2.65 parts by weight of polyether-type polyurethane prepolymer B compounded), and 1 part by weight of [unclear text - likely a continuation of the previous sentence]. Silicone foam stabilizer L-580 (Yantai Shunda Polyurethane Co., Ltd.), 0.1 parts by weight of A-1 catalyst (CAS: 3033-62-3, Shanghai Hanyu Chemical Co., Ltd.), 0.1 parts by weight of A-33 catalyst (33% triethylenediamine solution, CAS: 280-57-9, Shanghai Hanyu Chemical Co., Ltd.), 0.09 parts by weight of antioxidant 1010 (Shanghai Aladdin Biochemical Technology Co., Ltd.), and 0.01 parts by weight of antioxidant 168 (Shanghai Aladdin Biochemical Technology Co., Ltd.).

[0041] A method for preparing a high-strength, high-tear-resistance polyurethane foam includes the following steps: Step 1: At room temperature, add 36 parts by weight of polypropylene glycol PPG-2000 and 16 parts by weight of polytetrahydrofuran ether PTMEG-2000 to a high-speed dispersion vessel and stir at 800 rpm for 8 minutes. After mixing evenly, add 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 1 part by weight of silicone foam stabilizer L-580, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168 to the high-speed dispersion vessel and stir at 800 rpm for 8 minutes to mix evenly to obtain a mixture. Step 2: Add 35 parts by weight of TDI-80 / 20 and 5 parts by weight of dynamic crosslinking agent - polyether polyurethane prepolymer to the high-speed dispersion vessel, and stir at 1600 rpm for 6 min. Step 3: Immediately pour the uniformly mixed rigid polyurethane foam resin into the mold and foam until the foam interface is stable. Adjust the temperature to 65℃ and cure for 24 hours. Demolding will then yield a high-strength, high-tear-resistance polyurethane sponge.

[0042] The difference between Example 2 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from the following raw materials: 35 parts by weight of TDI-80 / 20, 33.4 parts by weight of polypropylene glycol PPG-2000, 18.6 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0043] The difference between Example 3 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from the following raw materials: 35 parts by weight of TDI-80 / 20, 37.14 parts by weight of polypropylene glycol PPG-2000, 14.86 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0044] The difference between Comparative Example 1 and Example 1 is that the polyurethane foam is made from the following raw materials: 46 parts by weight of TDI-80 / 20, 80 parts by weight of polypropylene glycol PPG-2000, 20 parts by weight of polyether polyol POP36 / 28 (Shanghai Hongzhuang Chemical Technology Co., Ltd.), 3 parts by weight of deionized water, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0045] The difference between Comparative Example 2 and Example 1 is that a polyurethane foam is made from the following raw materials: 35 parts by weight of TDI-80 / 20, 52 parts by weight of polypropylene glycol PPG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0046] The difference between Comparative Example 3 and Example 1 is that a polyurethane foam is made from the following raw materials: 35 parts by weight of TDI-80 / 20, 52 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0047] Performance testing: 1. The rebound rate was determined in accordance with GB / T 6670-2008 "Determination of rebound performance of flexible foam polymer materials by falling ball method".

[0048] 2. Compression set shall be determined in accordance with GB / T 6669-2008 "Determination of Compression Set of Flexible Foam Polymer Materials".

[0049] 3. Tensile strength and elongation at break were determined in accordance with GB / T6344-2008 "Determination of Tensile Strength and Elongation at Break of Flexible Foam Polymer Materials".

[0050] 4. Tear strength was determined in accordance with GB / T10808-2006 "Determination of tear strength of porous polymer elastic materials".

[0051] 5. The air permeability was determined in accordance with ISO 9237:1995 "Textiles - Determination of air permeability of fabrics".

[0052] Table 1: Test parameters of polyurethane foam in Examples 1-3 and Comparative Examples 1-3 As can be seen from Example 1 and Comparative Example 1, and Table 1, compared with conventional polyurethane foam, the polyurethane foam of the present invention has a tensile strength ≥200 Kpa, tear strength ≥6.0 N / cm, elongation at break ≥250%, air permeability 1000-1500 mm / s, compression set ≤8.0%, and resilience ≥35%, exhibiting good tensile and tear resistance, as well as good resilience and resistance to compression set.

[0053] Based on Examples 1-3 and Comparative Examples 2-3, and referring to Table 1, it can be seen that polypropylene glycol and polytetrahydrofuran ether glycol are compounded in a molar ratio of (1.8-2.5):1 to form a polyol, which can improve the resilience, compression set resistance, tensile properties (tensile strength ≥200 kPa, elongation at break ≥250%), and tear resistance (tear strength ≥6.0 N / cm) of polyurethane foam. Preferably, the molar ratio of polypropylene glycol to polytetrahydrofuran ether glycol is controlled at (2.2-2.3):1.

[0054] The difference between Example 4 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 37.14 parts by weight of polypropylene glycol PPG-2000, 14.86 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 2.5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0055] The difference between Example 5 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 37.14 parts by weight of polypropylene glycol PPG-2000, 14.86 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 6.5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0056] The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 does not contain the dynamic crosslinking agent - polyether-type polyurethane prepolymer. A polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 37.14 parts by weight of polypropylene glycol PPG-2000, 14.86 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0057] The difference between Comparative Example 5 and Example 1 is that: a polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 37.14 parts by weight of polypropylene glycol PPG-2000, 14.86 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 1.0 part by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0058] The difference between Comparative Example 6 and Example 1 is that: a polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 37.14 parts by weight of polypropylene glycol PPG-2000, 14.86 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 7.0 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0059] Table 2: Test parameters of polyurethane foam in Examples 1, 4-5 and Comparative Examples 4-6 Based on Examples 1, 4-5, and Comparative Examples 4-6, and in conjunction with Table 2, it can be seen that the addition of an appropriate amount of dynamic crosslinking agent can improve the tensile strength, tear resistance, resilience, and compression set resistance of polyurethane foam. However, if the amount added is too low, it will not have any effect, while if the amount added is too high, it will lead to a significant decrease in elongation at break, failing to meet the performance standard of elongation at break ≥250%. Therefore, the amount of dynamic crosslinking agent-polyether type polyurethane prepolymer added should be controlled at 2.5-6.5 parts, with the preferred addition range being 4.5-5.5 parts.

[0060] The difference between Example 6 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 1.95 parts by weight of polyoxyethylene diamine, 0.85 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0061] The difference between Example 7 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 1.45 parts by weight of polyoxyethylene diamine, 0.95 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0062] The difference between Example 8 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 3.75 parts by weight of polyoxyethylene diamine (weight average molecular weight Mw=1000, CAS:24991-53-5, Shanghai Aladdin Biochemical Technology Co., Ltd.), 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0063] The difference between Example 9 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from 57.24 parts by weight of carbodiimide-modified MDI (MDI-100LL, Yantai Wanhua Polyurethane Co., Ltd.), 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 1.75 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0064] The difference between Example 10 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from 40 parts by weight of TDI-80 / 20, 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 1.75 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0065] The difference between Comparative Example 7 and Example 1 is that: a polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 1.15 parts by weight of 3-methyl-1,5-pentanediol (Shanghai Aladdin Biochemical Technology Co., Ltd.), 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0066] The difference between Comparative Example 8 and Example 1 is that: a polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 5.75 parts by weight of polyoxyethylene diamine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0067] The difference between Comparative Example 9 and Example 1 is that: a polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 1.25 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0068] The difference between Comparative Example 10 and Example 1 is that: a polyurethane foam is made from 35 parts by weight of TDI-80 / 20, 36 parts by weight of polypropylene glycol PPG-2000, 16 parts by weight of polytetrahydrofuran ether PTMEG-2000, 1.5 parts by weight of polyoxyethylene diamine (weight average molecular weight Mw=400, CAS:24991-53-5, Shanghai Maclean Biochemical Technology Co., Ltd.), 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0069] Table 3: Test parameters of polyurethane foam in Examples 1, 6-10 and Comparative Examples 7-10 Based on Examples 1, 6-7, and Comparative Examples 7-9, and in conjunction with Table 3, it can be seen that the total addition amount of polyoxyethylene diamine and N-aminoethylpiperazine is 2.0-4.5 parts, and the mass ratio of polyoxyethylene diamine to N-aminoethylpiperazine is (2-4):1, which is beneficial to improving the tensile and tear resistance of polyurethane foam.

[0070] Based on Examples 1 and 6-7 and Table 3, it can be seen that when the mass ratio of polyoxyethylene diamine to N-aminoethylpiperazine is (2.2-2.3):1, the overall performance of the polyurethane foam is relatively better.

[0071] Based on Examples 1, 8, and Comparative Example 10, and in conjunction with Table 3, it can be seen that the weight-average molecular weight (Mw) of polyoxyethylene diamine is best controlled between 500 and 1000, resulting in better overall performance of the polyurethane foam. However, a lower weight-average molecular weight of polyoxyethylene diamine will affect the elongation at break of the polyurethane foam (below the 250% standard).

[0072] Based on Examples 1 and 9 and Table 3, it can be seen that the polyurethane foam synthesized using MDI-100LL has good tensile strength and tear strength, and although the elongation at break is relatively poor, it still meets the standard of ≥250%.

[0073] Based on Examples 1 and 10 and Table 3, it can be seen that as the TDI-80 / 20 content increases, the R value increases, the crosslinking density within the polyurethane foam increases, and the synthesized polyurethane foam exhibits higher tensile strength, tear strength, and compression set, while the elongation at break decreases but still meets the standard of ≥250%. However, as the TDI-80 / 20 content increases, the elongation at break will eventually be <250%. Therefore, when using TDI-80 / 20 as a diisocyanate, it is recommended to control the addition amount of TDI-80 / 20 to between 35 and 42 parts.

[0074] Based on Examples 1-10 and Comparative Examples 1-10, and in conjunction with Tables 1-3, it can be seen that in this invention, polyoxyethylene diamine, N-aminoethylpiperazine, and a dynamic crosslinking agent are used synergistically. The total amount of polyoxyethylene diamine and N-aminoethylpiperazine added is 2.0-4.5 parts, and the mass ratio of polyoxyethylene diamine to N-aminoethylpiperazine is (1.5-5):1. The total amount of dynamic crosslinking agent added is 2.5-6.5 parts, and the molar ratio of polypropylene glycol with a molecular weight of 2000 to polytetrahydrofuran ether glycol with a molecular weight of 2000 is (2-3):1. This improves the tensile strength (tensile strength ≥200 Kpa, elongation at break ≥250%) and tear resistance (tear strength ≥6.0 N / cm) of the polyurethane foam. At the same time, it also ensures that the prepared polyurethane foam still maintains good resilience (resilience ≥35%) and resistance to compression set (≤8%).

[0075] The difference between Example 11 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from the following raw materials: 35 parts by weight of TDI-80 / 20, 34.66 parts by weight of polypropylene glycol PPG-2000, 15.04 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.95 parts by weight of organophosphorus halide reactive flame retardant V68 (Jiangsu Yake Technology Co., Ltd.), 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0076] The difference between Example 12 and Example 1 is that: a high-strength, high-tear-resistance polyurethane foam is made from the following raw materials: 35 parts by weight of TDI-80 / 20, 32.66 parts by weight of polypropylene glycol PPG-2000, 15.04 parts by weight of polytetrahydrofuran ether PTMEG-2000, 5.5 parts by weight of organophosphorus halide reactive flame retardant V68 (Jiangsu Yake Technology Co., Ltd.), 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168.

[0077] Table 4: Test parameters of polyurethane foam in Examples 1 and 11-12 Based on Examples 1 and 11-12 and Table 4, it can be seen that the flame retardant rating of Example 1 without the addition of organophosphorus halogen reactive flame retardant can reach HB level. As the content of organophosphorus halogen reactive flame retardant V68 increases, the flame retardant performance of the synthesized polyurethane foam increases. When the content of organophosphorus halogen reactive flame retardant V68 is greater than 2%, the flame retardant rating of the polyurethane foam can reach V1 level. When the content of organophosphorus halogen reactive flame retardant V68 is greater than 5%, the flame retardant rating of the polyurethane foam can reach V0 level. It can also ensure that the polyurethane foam still maintains good tensile strength, tear resistance, resilience, and resistance to compression set.

[0078] It should be noted that this specific embodiment is merely an explanation of the technical solution of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A high-strength, high-tear-resistance polyurethane foam, characterized in that: It is made from the following raw materials in parts by weight: 35-60 parts diisocyanate, 40-75 parts polyol, 2-4.5 parts functionalized chain extender, 2.5-6.5 parts dynamic crosslinking agent, 1.5-4.0 parts foaming agent, 0.1-0.5 parts catalyst, 0.8-1.6 parts foam stabilizer, and 0.05-0.20 parts antioxidant; wherein the functionalized chain extender is polyoxyethylene diamine and N-aminoethylpiperazine with a molecular weight of 500-1000; the R value of the high-strength, high-tear-resistance polyurethane foam is 1.0-1.25; and the polyol has a molecular weight of 1500-3... The composition includes 000% polypropylene glycol and polytetrahydrofuran ether glycol; the molar ratio of polypropylene glycol to polytetrahydrofuran ether glycol is (1.8-2.5):1; the mass ratio of polyoxyethylene diamine with a molecular weight of 500-1000 to N-aminoethylpiperazine is (1.5-5):1; the dynamic crosslinking agent is polyether-type polyurethane prepolymer A with an NCO content of 3-5% and polyether-type polyurethane prepolymer B with an NCO content of 3-5%, wherein polyether-type polyurethane prepolymer A contains furan groups and polyether-type polyurethane prepolymer B contains maleimide groups.

2. The high-strength, high-tear-resistance polyurethane foam according to claim 1, characterized in that: The functionalized chain extender is polyoxyethylene diamine and N-aminoethylpiperazine. The polyoxyethylene diamine has a weight-average molecular weight (Mw) of 600, CAS: 24991-53-5, and is manufactured by Shanghai Aladdin Biochemical Technology Co., Ltd. The mass ratio of the polyoxyethylene diamine to the N-aminoethylpiperazine is 3:

1.

3. The high-strength, high-tear-resistance polyurethane foam according to claim 1, characterized in that: The polyol is a composition of polypropylene glycol PPG-2000 and polytetrahydrofuran ether PTMEG-2000, wherein the molar ratio of polypropylene glycol PPG-2000 and polytetrahydrofuran ether PTMEG-2000 is 2.25:

1.

4. The high-strength, high-tear-resistance polyurethane foam according to claim 1, characterized in that: The catalyst is catalyst A-1 or catalyst A-33; the foam stabilizer is an organosilicon foam stabilizer; the organosilicon foam stabilizer includes at least L-580; and the foaming agent is water.

5. The high-strength, high-tear-resistance polyurethane foam according to claim 1, characterized in that: The diisocyanate is at least one of MDI, TDI, and carbodiimide-modified MDI.

6. The high-strength, high-tear-resistance polyurethane foam according to claim 1, characterized in that: The high-strength, high-tear-resistance polyurethane foam has a tensile strength ≥200 kPa, a tear strength ≥6.0 N / cm, an elongation at break ≥250%, an air permeability of 1000-1500 mm / s, a compression set ≤8.0%, and a resilience ≥35%.

7. A high-strength, high-tear-resistance polyurethane foam, characterized in that: Made from the following raw materials: 35 parts by weight of TDI-80 / 20, 34.66 parts by weight of polypropylene glycol PPG-2000, 15.04 parts by weight of polytetrahydrofuran ether PTMEG-2000, 2.95 parts by weight of organophosphorus halide reactive flame retardant V68 from Jiangsu Yake Technology Co., Ltd., 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 The composition includes, by weight, dynamic crosslinking agent - polyether-type polyurethane prepolymer, 1 part by weight of silicone foam stabilizer L-580, 0.1 part by weight of catalyst A-1, 0.1 part by weight of catalyst A-33, 0.09 parts by weight of antioxidant 1010, and 0.01 part by weight of antioxidant 168; the polyoxypropylene glycol PPG-2000, polytetrahydrofuran ether PTMEG-2000, and organophosphorus halide reactive flame retardant V68 constitute a polyol. The method for synthesizing the dynamic crosslinking agent-polyether type polyurethane prepolymer includes the following steps: S1. Synthesis of polyether-type polyurethane prepolymer A: Under nitrogen protection, 34.84g of TDI-80 from Lanxing Chemical Co., Ltd. and 100g of DMF were mixed evenly, and then 12.82g of 2,5-furandimethylol from Shanghai Maclean Biochemical Technology Co., Ltd. and 0.02g of bismuth isooctanoate from Shanghai Maclean Biochemical Technology Co., Ltd. were added. The temperature was adjusted to 75℃ and the reaction was carried out for 2 hours. The -NCO content in the system was sampled and tested until the -NCO content reached the theoretical value. Then, 120g of polytetrahydrofuran ether PTMEG-600 was added. The polytetrahydrofuran ether PTMEG-600 is BASF PolyTHF. 600, reacted at 75℃ for 2 hours, and the -NCO content in the system was measured until the -NCO content was 0. Then, 34.84g of TDI-80 was added, and the reaction was carried out at 75℃ for 2 hours to end-cap. DMF was removed by vacuum distillation to obtain polyether polyurethane prepolymer A. The -NCO content in the obtained polyether polyurethane prepolymer A was 4.14%. S2. Synthesis of polyether-type polyurethane prepolymer B: Under nitrogen protection, 9.20g of amino-1,3-propanediol from Shanghai Yuanye Biotechnology Co., Ltd. and 100g of DMF were mixed evenly, and then 21.42g of 4-(maleimide)phenyl isocyanate from Shanghai Maclean Biochemical Technology Co., Ltd. were added. The temperature was adjusted to 45℃ and the reaction was carried out for 2 hours. The -NCO content in the system was sampled and tested until the -NCO content was 0. Then, 34.84g of TDI-80 was added, and the temperature was adjusted to 75℃ and the reaction was carried out for 2 hours. The -NCO content in the system was sampled and tested until the -NCO content reached the theoretical value. Then, 120g of polytetrahydrofuran ether PTMEG-600 was added. The polytetrahydrofuran ether PTMEG-600 is BASF PolyTHF. 600, reacted at 75℃ for 2 hours, and the -NCO content in the system was measured until the -NCO content was 0. Then, 34.84g of TDI-80 was added, and the reaction was carried out at 75℃ for 2 hours to end-cap. DMF was removed by vacuum distillation to obtain polyether polyurethane prepolymer B. The -NCO content in the obtained polyether polyurethane prepolymer B was 3.66%. S3. Weigh 2.35 parts by weight of polyether-type polyurethane prepolymer A and 2.65 parts by weight of polyether-type polyurethane prepolymer B, and mix them at 300 rpm for 8 minutes at room temperature to obtain the finished dynamic crosslinking agent.

8. A high-strength, high-tear-resistance polyurethane foam, characterized in that: It is made from the following raw materials: 35 parts by weight of TDI-80 / 20, 32.66 parts by weight of polypropylene glycol PPG-2000, 15.04 parts by weight of polytetrahydrofuran ether PTMEG-2000, 5.5 parts by weight of organophosphorus halide reactive flame retardant V68 from Jiangsu Yake Technology Co., Ltd., 2.25 parts by weight of polyoxyethylene diamine, 0.75 parts by weight of N-aminoethylpiperazine, 3 parts by weight of deionized water, 5 parts by weight of dynamic crosslinking agent - polyether type polyurethane prepolymer, 1 part by weight of organosilicon foam stabilizer L-580, 0.1 parts by weight of A-1 catalyst, 0.1 parts by weight of A-33 catalyst, 0.09 parts by weight of antioxidant 1010, and 0.01 parts by weight of antioxidant 168; wherein the polypropylene glycol PPG-2000, polytetrahydrofuran ether PTMEG-2000, and organophosphorus halide reactive flame retardant V68 constitute a polyol; The method for synthesizing the dynamic crosslinking agent-polyether type polyurethane prepolymer includes the following steps: S1. Synthesis of polyether-type polyurethane prepolymer A: Under nitrogen protection, 34.84g of TDI-80 from Lanxing Chemical Co., Ltd. and 100g of DMF were mixed evenly, and then 12.82g of 2,5-furandimethylol from Shanghai Maclean Biochemical Technology Co., Ltd. and 0.02g of bismuth isooctanoate from Shanghai Maclean Biochemical Technology Co., Ltd. were added. The temperature was adjusted to 75℃ and the reaction was carried out for 2 hours. The -NCO content in the system was sampled and tested until the -NCO content reached the theoretical value. Then, 120g of polytetrahydrofuran ether PTMEG-600 was added. The polytetrahydrofuran ether PTMEG-600 is BASF PolyTHF. 600, reacted at 75℃ for 2 hours, and the -NCO content in the system was measured until the -NCO content was 0. Then, 34.84g of TDI-80 was added, and the reaction was carried out at 75℃ for 2 hours to end-cap. DMF was removed by vacuum distillation to obtain polyether polyurethane prepolymer A. The -NCO content in the obtained polyether polyurethane prepolymer A was 4.14%. S2. Synthesis of polyether-type polyurethane prepolymer B: Under nitrogen protection, 9.20g of amino-1,3-propanediol from Shanghai Yuanye Biotechnology Co., Ltd. and 100g of DMF were mixed evenly, and then 21.42g of 4-(maleimide)phenyl isocyanate from Shanghai Maclean Biochemical Technology Co., Ltd. were added. The temperature was adjusted to 45℃ and the reaction was carried out for 2 hours. The -NCO content in the system was sampled and tested until the -NCO content was 0. Then, 34.84g of TDI-80 was added, and the temperature was adjusted to 75℃ and the reaction was carried out for 2 hours. The -NCO content in the system was sampled and tested until the -NCO content reached the theoretical value. Then, 120g of polytetrahydrofuran ether PTMEG-600 was added. The polytetrahydrofuran ether PTMEG-600 is BASF PolyTHF. 600, reacted at 75℃ for 2 hours, and the -NCO content in the system was measured until the -NCO content was 0. Then, 34.84g of TDI-80 was added, and the reaction was carried out at 75℃ for 2 hours to end-cap. DMF was removed by vacuum distillation to obtain polyether polyurethane prepolymer B. The -NCO content in the obtained polyether polyurethane prepolymer B was 3.66%. S3. Weigh 2.35 parts by weight of polyether-type polyurethane prepolymer A and 2.65 parts by weight of polyether-type polyurethane prepolymer B, and mix them at 300 rpm for 8 minutes at room temperature to obtain the finished dynamic crosslinking agent.

9. A method for preparing a high-strength, high-tear-resistance polyurethane foam according to any one of claims 1-8, characterized in that: Includes the following steps: Step 1: Measure the polyols according to the formula, mix them evenly, and then add the functionalized chain extender, foaming agent, catalyst, foam stabilizer, and antioxidant and mix evenly to obtain a mixture. Step 2: Add diisocyanate and dynamic crosslinking agent to the mixture and mix evenly to obtain rigid polyurethane foam resin; Step 3: Pour the foam into a mold at room temperature and let it foam until the foam interface is stable. Adjust the temperature to 60-80℃ and cure for 24-36 hours. Demolding will then yield high-strength, high-tear-resistance polyurethane foam.

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