超高分子量聚乙烯凝胶结晶膜的结晶形态X射线衍射研究

对由准稀溶液速冷凝胶化结晶方法制备的超高分子量聚乙烯(UHMWPE)膜,应用广角及小角X射线衍射进行了研究,证明所形成的膜是片晶-分子链折叠的层积状结构。片晶折叠链的分子链方向(即C轴方向)垂直于膜面,在片晶间无规排列的分子链平行膜面,具有较强的“排列”取向,片晶-无规排列链形成的大点阵间距为109(?),片晶间的无规排列链沿垂直分子链方向的统计平均间距约为4.6(?),分子链数约为4～5。这一结果在超拉伸过程中,有利于从片晶-折叠分子链到完全伸直链的转变,从而可获得超高拉伸比(λ>200)。

X-ray Diffraction Study for Morphology of Ultra-high Molecular Weight Polyethylene Produced by Gelation/Crystallization

Ultra-high molecular weight polyethylene (UHMWPE) gel films are prepared by gelation/crystallization from a semidilute solution. The obtained samples are investigated with wide and small angle X-ray diffraction. The results confirm that the gel films are composed of alternating mat textures of large crystal lamellae whose flat faces parallel the film surface and the random folded-chains that intervene between the two lamellae, that the chain c-axes in the lamellae are oriented perpendicular to the film surface, while the random folded-chains are directed parallel to the film surface. The long spacing is approximated as 110A, the interchain distance along the direction normal to the chains in random folded-chain layer average 4.6A. Therefore, between the two lamellae there are 4 or 5 for the random folded-chains. The feature is thought to be favorable to transformation of the lamellae into completed microfibrillar structure, to assure ultradrawing up to high draw ratios.