含少量共聚组分聚乙烯熔体拉伸薄膜的形态结构

Morphological Structure of Melt-drawn Films of Polyethylene Containing Small Amount of Copolymerized Component

利用透射电子显微学(TEM)和示差扫描量热学(DSC)等方法研究了含少量丁烯-1组分(摩尔分数为0.64%)的聚乙烯共聚物(PE100)熔体拉伸高取向薄膜的形态结构.结果表明,在PE100熔体拉伸薄膜中,除存在高取向片晶结构外,还含有大量的纤维晶,纤维晶平行于拉伸方向,穿过几个片晶区,平均直径约为12nm.模拟实验结果表明,纤维晶的生成源于聚乙烯共聚物中的超高分子量组分,但不同于传统意义上的伸直链纤维晶,其形态特征应为晶桥结构.由此提出了晶桥结构纤维晶模型,该模型不但有助于深入理解和认识聚合物取向结晶机理,同时也为该材料的高性能化提供了理论依据.

The morphological structures of melt-drawn films of polyethylene containing small amount of copolymerized component[0. 64% （molar fraction） of butylene-1 ] were studied by TEM and DSC techniques. The results indicate that, in addition to highly oriented lamellae, the melt-drawn films of the polyethylene copolymer contain large amount of fibrous crystals with average diameter about 12 nm, which are parallel to drawing direction. Simulation experiment [ adding 1% （mass fraction ） ultra-high molecular weight polyethylene （UHMWPE） into regular high density polyethylene] proves that the formation of the fibrous crystals originates from ultra-high molecular weight component in the polyethylene copolymer. However, this kind of fibrous crystal is different from classical extended chain fibrous crystal. Morphological characteristics of the fibrous crystal of the copolymer should be crystal-bridged structure with an alternating alignment of crystalline and noncrystalline regions. A model of crystal-bridged fibrous crystal was proposed, which not only benefits understanding the mechanism of the oriented crystallization of polymers, but also provides a theory foundation for improving the properties of the material.