Analysis of contributing factors to production of highly transparent isotactic polypropylene extrusion sheets. Part 2

Abstract

Abstract To obtain highly transparent isotactic polypropylene (PP) sheet by an industrial process, the influences of the isotacticity and metallocene linear low‐density polyethylene (L‐LDPE) as crystallization control material were analyzed. The sheet samples were extruded by using a direct single‐belt process. Even if the sheeting was carried out under the same conditions, the lower tacticity PP generated the less and the smaller size of spherulites. Low‐tacticity PP showed improvement on transparency by heat treatment as well as the high‐tacticity PP. Moreover, the behavior of transparency was investigated by 10 wt% addition of various L‐LDPE with wide range density. Thanks to the fine distribution particles of L‐LDPE in PP matrix, the number of generated spherulites and the growth rate of them were restrained. In the case of addition of L‐LDPE with the specific density to PP, the transparency was markedly improved by the heat treatment. According to the density of added L‐LDPE, the suitable heat‐treatment temperature condition, which showed the best transparency, was changed. This phenomenon could be explained by the refractive index difference of PP matrix and the fine distribution particles of L‐LDPE. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers