亲水聚丙烯/聚乙烯醇缩丁醛共混物的非等温结晶动力学及形貌

Morphology and Non-Isothermal Crystallization Kinetics of Hydrophilic Polypropylene / Polyvinyl Butyral Blends

以聚乙烯醇缩丁醛(PVB)为亲水改性剂,聚丙烯(PP)为基材,聚丙烯接枝马来酸酐(PP-g-MAH)为相容剂,通过熔融挤出制备亲水PP/PVB共混物。采用差示扫描量热分析表征PP/PVB共混物结晶性能,通过计算非等温结晶动力学,分析研究PVB对PP基体结晶行为的影响;采用偏光显微镜及X射线衍射研究PVB的添加对PP/PVB共混物中PP基体晶体形貌与晶型的影响;采用水接触角(WCA)测试了PP/PVB共混物的亲水性能。结果显示,PVB的加入可以起到异相成核作用,加快PP的成核速率,改变PP基体球晶成核生长方式。但过量添加时会阻碍PP分子链段运动,导致晶体结构不完善,同时也会阻碍PP球晶的进一步生长,使得球晶尺寸降低,球晶间的边界消失。PP/PVB共混物的亲水性得到极大改善,随着PVB含量的增加,WCA从纯PP的102.9°降低到76.7°。

Polyvinyl butyral (PVB) as hydrophilic modification agent and polypropylene-g-maleic anhydride (PP-g-MAH) as compatibilizer were blended with PP to prepare hydrophilic PP/PVB blends by melt extrusion. Firstly, crystallization properties of PP/PVB blends were characterized by differential scanning calorimeter(DSC), and the effect of PVB on the crystallization behavior was investigated by calculating the non-isothermal crystallization kinetics. Secondly, the polarizing microscope and XRD were used to analyze effects of PVB on the crystal morphology and crystal forms. In addition, the hydrophilicity of PP/PVB blends was tested by water contact angle (WCA). The results show that the addition of PVB can change the crystallization mechanisms of PP and accelerate the nucleation rate of PP because of the heterogeneous nucleation of PVB. However, the excessive addition of PVB delays the motion of molecular chains and the growth of spherulites, leads to an imperfect crystal structure and reduces spherulites sizes simultaneously. Meanwhile, the boundaries between spherulites disappear. The hydrophilicity of PP /PVB blends is improved significantly, WCA of PP/PVB blends reduces from 102.9° to 76.7° with the increase of PVB.