乙烯–丙烯酸甲酯对聚甲醛热氧老化性能的影响

采用挤出成型制备出了具有优异韧性的乙烯–丙烯酸甲酯共聚物(EMA)改性聚甲醛(POM),研究了EMA对POM热氧老化性能的影响。采用万能拉力机、广角X射线衍射仪和蠕变仪对不同老化时间的纯POM和EMA改性POM的力学性能、结晶性能及蠕变性能进行了对比分析。结果表明,EMA的加入明显提高了POM的韧性,当EMA质量分数为9%时,其改性的POM冲击强度和断裂伸长率分别比纯POM提高了13%和97%,而拉伸和弯曲强度仅下降了4.5%和8.0%,结晶度和耐蠕变性也略有下降。EMA的加入并没有劣化POM的热氧老化性能,随老化时间的增加,EMA改性POM的拉伸和弯曲强度、结晶度、蠕变性能变化趋势与纯POM基本相同,在30 d老化时间内,其冲击强度和断裂伸长率的下降幅度较大,但仍高于相同老化时间下的纯POM,且在老化早期,EMA改性POM的韧性仍高于未老化时的纯POM,表明其可应用于汽车方向盘轴承链等需要材料具有较好韧性的零件部位。

Effects of Ethylene-methyl Acrylate on Thermal-oxidative Ageing properties of Polyformaldehyde

Ethylene-methyl acrylate copolymer (EMA) modified polyformaldehyde (POM) with excellent toughness was pre-pared by extrusion molding and the effects of EMA on the thermal-oxidative aging properties of POM were studied. The mechani-cal properties,crystallinity and creep resistance of POM and EMA modified POM were comparatively analyzed by using universal testing machine,wide angle X-ray diffraction and creepmeter. The results show that the toughness of EMA modified POM in which the mass fraction of EMA is 9% was obviously improved,and comparing to pure POM,the impact strength and elongation at break increase by 13% and 97%,respectively,the tensile strength andflexural strength only decrease by 4.5% and 8.0%,respectively, the crystallinity and creep resistance have slight decrease. However,the adding of EMA don′t cause the deterioration of thermal ag-ing properties of POM. With increasing aging time,the tensile strength,flexural strength,crystallinity and creep properties of EMA modified POM and pure POM had comparable change trend,the impact strength and elongation at break of EMA modified POM decrease more greatly than pure POM within 30 aging days but still are higher than those of pure POM at the same aging time,how-ever,at early aging time,the toughness of EMA modified POM is still higher than pure POM which don′t experience aging,which indicates that EMA modified POM can be applied to the automobile parts such as steering wheel bearing chain etc. needing material has good toughness.