| Solvent-free adhesive is a kind of environmental friendly adhesive with 100% solid content which is safe, less material consumptive and just needs simple curing conditions. The curing mechanism of this adhesive is crosslinking happens between–NCO and–OH which are contained in two components respectively. As one kind of polyurethane adhesives, the solvent-free adhesive has similar characters: good wear resistance, water resistance, solvent resistance, ozone resistance and etc.; higher adhesion strength with polyester film, paper, fabric, metal and other materials. The drawback is the solvent-free adhesive is easier to hydrolyze. So, solving the problem about water resistance and boiling resistance of solvent-free is a difficulty and a key point of researching.This research started with viscosity and water resistance of solvent-free adhesive as entry point. In this paper, the polyurethane prepolymer (Component A) was synthesized with PBA, Castor oil, and IPDI as raw materials. Castor oil was modified with silane coupling agent and added to component B as modifier. The curing process of adhesive was studied too. Then, structure of synthesized products was analyzed by IR spectrum. NCO content and hydroxyl value of products were tested by chemical titration. In addition, water absorption, T style steel strength, boiling resistance and heat resistance of adhesives were also determined. The appropriate technological parameters were obtained through above analysis and compare.After several experiments, we have following conclusions: The best reaction conditions of preparing component A were 80℃and 3 hours; Appropriate R value was 2 or 3. The addition of castor oil reduced the viscosity of prepolymer and significantly improved the water resistance of cured adhesive, but slightly decreased the adhesion strength of adhesive. The proper R'value of two components was 1.3. The modified castor oil was able to remarkably accelerate the cuing process and the curing time was decrease from 7days to 36 hours. Besides, the water resistance, boiling resistance and thermal performance of cured adhesive were improved through modification with silane coupling agent. However, the amount of modified castor oil can't be too much. The optimum content was 60%. |
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