双向拉伸α聚丙烯制备微孔膜的研究

Study on the Fabrication of Microporous Membranes by Biaxially Stretching α-iPP

通过不同的加工方式(淬火以及在80、100、120℃下等温结晶)制备出不同热历史的α聚丙烯。接着利用差示扫描量热仪和偏光显微镜研究其熔融行为和结晶形态,发现淬火样品结晶度和熔融温度最低,球晶最小;另一方面,随着等温结晶温度的升高,样品的结晶度和熔融温度逐渐升高,球晶尺寸逐渐增大。进一步对样品进行双向拉伸制备出微孔膜,扫描电子显微镜测试结果显示,淬火样品由于球晶强度较低,双拉后材料没有产生微孔;而等温结晶样品由于晶体强度较高、球晶界面较弱,双拉后产生了大量微孔,其孔径尺寸随等温结晶温度的升高逐渐增大,孔径分布均匀性优异。

In this article, α-isotactic polypropylene samples with different thermal history were prepared by different processing methods （quenching, isothermal crystallization at 80, 100, 120 ℃ ）. Subsequently, their melting behavior was investigated by differential scanning calorimetry and the crystallization morphology was observed by micropolariscope. From the results we found that the crystallinity and melting temperature of the quenched samples are the lowest with the smallest spherulitic size. Besides, with the rising in isothermal crystallizing temperature, the crystallinity, melting temperature and spherulitic dimension increases. Then microporous membranes were obtained by the biaxial stretching of those samples. The results from scanning electronic microscopy show that the quenched sample do not generate micropores due to its low strength of spherulites. However, because the crystal strength is higher and spherulitic boundaries are weak, a large amount of micropores are created from the isothermal crystallized samples, and the pore size increases as the isothermal temperature increased, better pore size distribution uniformity is achieved.