THE EFFECT OF EC ON ORIENTATION AND RELAXATION OF PP OBTAINED VIA DYNAMIC PACKING INJECTION MOLDING

查看全文 作　　者：YongWang BingNa [1]QiangFu 机构地区：[1]CollegeofPolymerScienceandEngineering,SichuanUniversity,StateKeyLaboratoryofPolymerMaterialsEngineering,Chengdu610065,China 出　　处：《Chinese Journal of Polymer Science》索引2005年第23卷第1期,共9页 基　　金：This work was supported by the China National Distinguished Young Investigator Fund(No.29925413);National Natural Science Foundation of China(No.20274028;5037303);also partly supported by Ministry of Education of 摘　　要：As a long term project aiming at engineering plastics based on polypropylene (PP), in this work, we report the effect of ethylene-cellulose (EC) on the orientation and relaxation of PP obtained via dynamic packing injection molding(DPIM). 2d-WAXD results showed that PP with a highly oriented structure and a shish-kebab structure were achieved by DIPM, leading to an increase of tensile strength from 35.0 MPa to 48.6 MPa. The degree of orientation of PP was increased by adding only 1% of EC, resulting in a further increase of tensile strength from 48.6 MPa to 53.8 MPa. Shish was found to exist not only in the oriented layer but also in the core of the sample after adding EC, as evidenced by DSC result.This was understood as due to the overall decrease of viscosity by the addition of EC, thus an increasing of shear rate. Higher shear rate can favor the orientation of molecules and continuous growth of shish structure, resulting in a change of shish distribution along the sample thickness. On the other hand, the relaxation mode of shish in the melt recrystallization of PP is also greatly affected by the presence of EC. A retarded relaxation of PP macromolecules was seen.Even more, SEM results showed that EC could form the short fibers in PP matrix along the shear flow direction. Compared with the morphology obtained by conventional injection molding, a much better dispersion and easy break-up of EC in PP matrix were observed for samples obtained by dynamic packing injection molding. 关 键 词：注射成型工艺 动力学 聚丙烯 倾向性 重结晶