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采用熔融拉伸法制备聚丙烯微孔膜,在避免冷拉会自然回缩和热处理后样品需降温检测等因素对冷拉伸样品影响的情况下,在线研究了冷拉、热定型、热拉过程中样品结构变化.原位小角X射线散射检测与扫描电子显微镜、示差扫描量热仪结合深入研究了不同的冷拉拉伸比对微孔膜片晶和孔洞结构的影响.结果表明不同的冷拉伸比其成孔机理不同,冷拉15%,仅拉伸方向长周期发生微弱的变化,其成孔机理是冷拉产生缺陷,热拉成孔;冷拉30%拉伸主要是将薄弱片晶拉伸转变为不稳定的架桥,热定型阶段部分架桥断裂,竖直方向上产生明显的Streak信号;冷拉40%拉伸方向信号显示实际片晶长周期的增长率小于宏观应变,部分骨架片晶在冷拉阶段已被拉伸破坏成孔.随着冷拉拉伸比增大架桥长度变短,孔径减小,30%是制备微孔膜较合适的冷拉拉伸比.
Polypropylene microporous membrane was prepared by melt drawing method. Under the condition of avoiding the influence of the natural shrinkage of the cold drawing and the sample to be cooled after the heat treatment on the cold drawn sample, the effects of cold drawing, heat setting, heat drawing In-process sample structure changes in situ small-angle X-ray scattering detection and scanning electron microscopy, differential scanning calorimetry combined with different cold stretch ratio on the microporous film crystal and pore structure.The results show that different Cold drawing is different from the forming mechanism of the cold drawing, cold drawing 15%, weak stretching changes only in the long-term stretching direction, the hole forming mechanism is cold-drawn defects, hot drawn into the hole; The weak sheet crystal tensile transition to an unstable bridge, the heat-setting phase of the part of the bridge fracture, the vertical direction of the obvious Streak signal; cold pull 40% of the tensile direction of the signal shows the actual growth rate of the sheet crystal growth cycle is less than the macro Strain, part of the framework of lamellar crystal in the cold-drawing stage has been stretched to damage the hole into. With the cold-drawn stretch ratio increases the bridge length becomes shorter, the aperture decreases, 30% is the preparation of microporous film more suitable cold-pulling Stretch ratio.