考察了热塑性酚醛树脂(Novolak)增容聚甲醛 (POM)／丁腈橡胶(NBR)共混物的力学性能、断裂形貌和结晶形态。研究发现,POM与NBR 共混 后由于不相容而导致共混物力学性能下降;共混物中添加Novolak后,在NBR含量为40%时发生 “脆-韧”转变;其中NBR-26对POM的增韧效果最佳。断裂形貌考察表明,POM／NBR共混物的 断裂面呈脆性断裂特征;而添加Novolak后,共混物断裂面呈现延性断裂并出现丝状牵伸物。对共混物结晶形态观察发现,POM／NBR共混物中POM易形成大球晶,这是导致共混物缺口冲击强度下降的重要原因;而在共混物中添加Novolak后,Novolak通过与POM分子链间的相互作用,改变了POM分子链固有的规程和排列方式,从而改变了POM的结晶形态,使球晶显著减小并消失。
The mechanical properties, fracture morpho logy, and crystallite of polyacetal(POM) and nitrile-butadiene(NBR) blends comp atibilized with Novolak were investigated. It is found the POM and NBR are immis cible system, and the interface adhesion and compatibilization of POM and Novola k in blends can be improved by addition of Novolak. As a result, Izod impact str ength of blends increases remarkblely. The impact fracture surface showed a toug h morphology for POM／NBR／Novolak blends and brittle one for POM／NBR blends. T he crystallite morphology of the blends under polarized light microscopy demonst rated that the size of spherulites of POM／NBR blends was so large as to increas e the brittleness of blends. The size of spherulites of blends could be sharply reduced by mixing with Novolak, which suggested that Novolak could diminish the inner stress concentration in blends and improve the toughness of blends.
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