邻苯二甲酸二正烷基酯类稀释剂的烷基长度对热致相分离制备聚丙烯微孔膜的影响

通过对等规聚丙烯与邻苯二甲酸二正烷基酯体系的相分离过程进行研究,绘制了等规聚丙烯与多种烷基长度的邻苯二甲酸二正烷基酯类稀释剂的相图.由相图发现,随着邻苯二甲酸二正烷基酯的烷基长度增加,浊点曲线向低温方向移动;而结晶曲线基本不受烷基长度的影响.采用基团贡献法计算溶度参数分量,并以此估算Flory-Huggins相互作用参数的变化趋势.通过比较微孔膜内部结构,发现随着烷基长度的增加,微孔的平均尺寸呈下降趋势,这是由于分散相液滴生长时间缩短和生长速率减小共同作用的结果.

Effect of the number of carbon atoms in the linear alkyl chain of dialkyl phthalate on polypropylene microporous membrane formation via thermally induced phase separation

The phase diagrams of isotactic polypropylene with various dialkyl phthalates which possess different carbon atoms in alkyl chain are determined.It is found experimentally that the liquid-liquid separation temperatures are shifted to lower temperature whereas the crystallization temperature curves change a little when the number of carbon atoms in alkyl of dialkyl phthalates increases. This phenomenon is interpreted by using solubility parameters to estimate the Flory-Huggins parameters.The resulting average pore sizes in the film associated with the polymer-lean phase decrease with the number of carbon atoms in alkyl increases.The decline of pore size is attributable to the shorter growth time due to the smaller temperature difference between binodal and crystallization temperature,and the slower coarsening rate because of lower super-cooling.