动态下HTDB/TDI体系凝胶化的研究

Study on the Gelation of Hydroxy-Teminated Polybutadiene/Diisocyanate Blends Under Dynamic Condition

利用哈克流变仪制备了热塑性聚丁二烯型聚氨酯。获得了反应挤出的工艺条件。研究表明 ,当不加催化剂时 ,由于反应温度比较高而使产物出现热交联 ,此交联产物不溶于沸腾的甲苯和二甲苯 ;当加入催化剂后 ,反应温度可大幅度下降 ,热交联消失。产物可溶于沸腾的二甲苯 ,但在甲苯中仍然存在物理性的凝胶 ,所以在甲苯中的凝胶含量不能作为反应程度的判据。虽然硬段的含量不到 1 0 % ,但凝胶含量可达到 90 %。利用甲苯抽提 ,研究了凝胶含量随剪切和时间的变化。

Thermoplastic polyurethane based on polybutadiene was prepared by using Haake mixer. Suitable technical conditions were obtained. It shows that relatively high temperature is needed if the blends react without catalyst, which may cause thermo-oxidization and crosslinking, so that the product is unsoluable in either boiling toluene or xylene; On the other hand, under the addition of catalyst, the reaction temperature can be lowered greatly,then thermo-crosslinking is avoided and the product is soluble in boiling xylene. However, some physical gel still exist in hot toluene,then the gel in toluene can not be reflected the extent of the reaction. The ultimate gel content could reach 90%,though the hard segment concentration is only less than 10%.By means of toluene extraction, the variation of the gel content with the shearing force and reactive time is also given.