不同老化方法对聚乙烯地膜结构和性能的影响

Effect of Different Aging Methods on the Structures and Properties of Polyethylene Mulch Films

聚乙烯(PE)地膜经过不同方法老化后的结构和性能变化不同,本文按固定配方制备了一种PE地膜,研究了该地膜经过不同方法老化后的拉伸性能和结构变化。结果表明,PE地膜在经过4种方法老化40 d后,化学结构的变化相似,只有热氧老化后在1261 cm-1出现C—O特征吸收峰;老化后地膜的熔融温度都有不同程度的下降,且结晶度有明显提高,未老化时的结晶度仅有1.7%,自然老化后结晶度提升最高为13.9%;地膜经过不同方法老化后,拉伸性能都有不同程度的下降,其中热氧光老化速度最快,在20 d时丧失拉伸性能,且横向PE地膜变化比纵向更为敏感;地膜在经过自然暴晒、热氧光老化后数均分子量都有不同程度的上升,重均分子量都有所下降,且热氧光老化后分子量分布明显变窄。

The structures and properties of polyethylene(PE)mulch films after aging by different methods are different.In this paper,one kind of PE mulch film was prepared according to a fixed formula,and its mechanical properties and structural changes after aging by different methods were studied.The results show that the chemical structures of PE films are similar after aging for 40 days by four methods,only the C—O characteristic absorption peak appears at 1261 cm-1 after thermo-oxidative aging.After aging,the melting temperature of the film decreases to different degrees,and the crystallinity increases obviously.The crystallinity is only 1.7%before aging,but the highest crystallinity is 13.9%after natural aging.After aging by different methods,the tensile properties of PE films have different degrees of decline.Among them,the speed of thermo-oxidative-photic aging is the fastest,and the mechanical properties of the films are lost after 20 d,the change of transverse PE film is more sensitive than that of longitudinal PE film.The number-average molecular weight of mulch film increases in different degrees after natural exposure and thermo-oxidative-photic aging,but the weightaverage molecular weight of mulch film decreases and the molecular weight distribution narrows significantly.