Polyurethane thermoplastic elastomer is hydroxy polyurethane, which has both high-strength plastics, high elasticity of rubber, and excellent abrasion resistance, which is 2 to 10 times that of natural rubber. Has excellent oil resistance, low temperature resistance, ozone resistance, radiation resistance and insulation, vibration absorption characteristics. Oil resistance can be comparable to nitrile rubber, and polyurethane thermoplastic elastomers have poor heat resistance. The long-term use temperature is about 800C. The water resistance is poor, and the infiltrated water forms hydrogen bonds with the polar groups in the elastomer. The hydrogen bonds between the molecules of the elastomer itself are weakened. Although the general polyurethane elastomer will change color when used for oxidation, the mechanical properties are basically unchanged.
Polyurethane thermoplastic elastomers can be dissolved in suitable solvents. They can also be modified with thermoplastic resins and rubbers to make solvent-based adhesives. They can be used as high-quality shoe adhesives to bond artificial leather and other soft PVC products. They are very good and can also be used as fabrics. And paper coating, enhance and waterproof effect.
1, polyurethane elastomer rubber
The structure of thermoplastic polyurethane elastomers contains a small amount of hydroxyl groups, also known as hydroxy polyurethanes, and can be synthesized by direct and chain extension methods. The hydroxypolyurethane has a high crystallization rate and a high initial tack strength; it has a large thermoplasticity and is easily dissolved; it has a large deformation and good flexibility.
2, polyurethane elastomer solvent
Polyurethane thermoplastic elastomers are non-toxic, odorless and soluble in solvents such as methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, and dimethylformamide. Also soluble in toluene, acetone, methyl ethyl ketone, ethyl acetate in a suitable mixture of mixed solvents, showing a colorless and transparent state, have better storage stability.
3, polyurethane elastomer adhesive preparation and modification
By dissolving the polyurethane thermoplastic elastic colloidal particles in an appropriate mixed solvent, a single-component adhesive with a solid content of 15% to 18% can be prepared, using a mixed solvent of acetone:toluene=70:30 (mass ratio), which can be made inexpensive Polyurethane adhesive; with methyl ethyl ketone: acetone = 60:40 (mass ratio) can be formulated as a non-toxic environmentally friendly adhesive. The above-mentioned one-component adhesive and polyisocyanate curing agent can be used to obtain a two-component polyurethane adhesive.
1%~20% of polymethyl methacrylate and polyurethane elastomer colloid dissolved in mixed solvent of butanone, acetone, toluene and ethyl acetate, and the initial viscosity and tensile strength of the adhesive are improved. .
12% of linear hydroxy polyurethane, 1 part of vinyl chloride-vinyl acetate copolymer, 0.9 part of chlorinated rubber, 0.1 part of adipic acid, 65 parts of acetone, and 12 parts of naphtha. The main agent is JQ-1. The agent, which has a greater initial tackiness, is produced by the adhesive.
Polyurethane 1,6 hexanediol-TDI polyurethane is added to 10% of 2402 resin, which can be made into a good adhesive. Adding 1% FeCl3 in 20% Desmocoll 400 ethyl acetate solution and using 1% polyisocyanate as a curing agent showed that the ferric chloride can improve the bonding strength and heat resistance.
In the polyurethane adhesive, 0.01 part of a crystal nucleating agent, such as 1-5 Î¼m rutile-type iron oxide, is added, and the initial adhesive strength and thermal stability of the adhesive are improved by 20% to 40% due to the formation of a large rubber-like structure in the adhesive.
By using 372 plastic, E-42 epoxy resin, No. 6 rubber, SBS, etc. as the tackifying resin and adding the polyurethane adhesive respectively, the initial tackiness and the final peel strength can be improved.
The type of curing agent has a great influence on the initial viscosity of polyurethane adhesives. TDI trimers (solids content 48% to 52%, viscosity 100 to 200 mPa.s) are used as curing agents, and the adhesives have good initial tack strength.
Bonding process also affects the performance of polyurethane adhesives. It is formulated with polyurethane elastomer 10~20g tackifying resin 4~8g, active agent 1~2g, and mixed solvent 100g. It is composed of polyisocyanate (Desmodur RFE) and catalyst. Into the B component. If the component B is used as a primer and the component is recoated, the peel strength and crack resistance of the adhesive after being mixed with A and B (A:B=100:15) are significantly improved.
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