Abstract: The morphological structures of melt-drawn films of polyethylene containing small amount of copo-lymerized 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.

Key words: Polyethylene copolymer, Oriented crystal, Crystal-bridged fibrous crystal