Two-component polyurethane adhesive has been improved in recent years, its variety, summarized as follows:
(1) Improvement of low-temperature resistance Polyurethane adhesives have good low-temperature resistance, which mainly refers to polyether-based adhesives, while polyester-polyurethane adhesives have poor low-temperature resistance. With the adhesive prepared from poly-ε-caprolactone, the low temperature resistance is also improved. In the preparation, the addition of the chain extender increases the molecular weight of the polyurethane, which promotes the improvement of the low temperature performance of the adhesive. However, because the crosslink density in the polyurethane structure is too high, the low-temperature performance of the adhesive is reduced. Therefore, after using a crosslinker having a longer molecular segment and a crosslinker having a hindered group, the disproportionation prevention is prevented. The large joints also improve the low-temperature resistance of the adhesive.
(2) Improvement of heat resistance The heat resistance of the polyurethane adhesive is poor, which is a major drawback. The use of isocyanate having a trimer or aromatic ring as a raw material can improve the heat resistance but increase the brittleness. Polyester type adhesives have better heat resistance due to the use of phthalic anhydride instead of adipic acid in the polyester type links, or the use of aromatic dihydric alcohols as chain extenders. Poly(ε-caprolactone)urethanes have higher temperature resistance than those of general polyurethane type adhesives.
(3) Improvement of hydrolysis resistance The polyester polyurethane has poor hydrolysis resistance and can be improved by adding a hydrolysis-resistant stabilizer such as carbodiimide. By incorporating a polyether-based binder in the polyester, its hydrolysis resistance can also be improved. Add 0.5% to 5% mass fraction of organic silane coupling agent in the adhesive, such as commonly used γ-aminopropyl triethoxysilane (KH-550), γ-glycidyl ether propyl trimethoxy Silane (KH-560), γ-mercaptopropyltrimethoxysilane, β-[3,4]-epoxy-cyclohexyl-ethylsilane, epoxypropyltrimethoxysilane, etc The hydrolysis resistance of the mixture. Poly ε-caprolactone polyurethane adhesives have much better hydrolysis resistance than general polyurethane adhesives.
(1) Improvement of low-temperature resistance Polyurethane adhesives have good low-temperature resistance, which mainly refers to polyether-based adhesives, while polyester-polyurethane adhesives have poor low-temperature resistance. With the adhesive prepared from poly-ε-caprolactone, the low temperature resistance is also improved. In the preparation, the addition of the chain extender increases the molecular weight of the polyurethane, which promotes the improvement of the low temperature performance of the adhesive. However, because the crosslink density in the polyurethane structure is too high, the low-temperature performance of the adhesive is reduced. Therefore, after using a crosslinker having a longer molecular segment and a crosslinker having a hindered group, the disproportionation prevention is prevented. The large joints also improve the low-temperature resistance of the adhesive.
(2) Improvement of heat resistance The heat resistance of the polyurethane adhesive is poor, which is a major drawback. The use of isocyanate having a trimer or aromatic ring as a raw material can improve the heat resistance but increase the brittleness. Polyester type adhesives have better heat resistance due to the use of phthalic anhydride instead of adipic acid in the polyester type links, or the use of aromatic dihydric alcohols as chain extenders. Poly(ε-caprolactone)urethanes have higher temperature resistance than those of general polyurethane type adhesives.
(3) Improvement of hydrolysis resistance The polyester polyurethane has poor hydrolysis resistance and can be improved by adding a hydrolysis-resistant stabilizer such as carbodiimide. By incorporating a polyether-based binder in the polyester, its hydrolysis resistance can also be improved. Add 0.5% to 5% mass fraction of organic silane coupling agent in the adhesive, such as commonly used γ-aminopropyl triethoxysilane (KH-550), γ-glycidyl ether propyl trimethoxy Silane (KH-560), γ-mercaptopropyltrimethoxysilane, β-[3,4]-epoxy-cyclohexyl-ethylsilane, epoxypropyltrimethoxysilane, etc The hydrolysis resistance of the mixture. Poly ε-caprolactone polyurethane adhesives have much better hydrolysis resistance than general polyurethane adhesives.
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