Polypropylene - Cellulose fibres composites. Part I. Influence of conditions of extrusion and injection processes on the structure of polypropylene matrix

Composites of iPP with flax fibers in amounts 5 or 10 wt.% either unmodified or modified with acetic anhydride, were obtained by extrusion. The samples were then injection molded from granulated products of composites (Table 1). Effects of temperature of extrusion head and injection mold as well as the effects of fibers' content and modification on hexagonal form (beta-iPP) part were characterized (Figs. 1-3, Table 2). Hexagonal form (beta-iPP) is an intermediate step between molten phase of a polymer and monoclinic form It has been stated than (beta-iPP) part depends mainly on temperature of mold and head. This phenomenon has been interpreted on the basis of shearing forces interactions during the processing, dependent on temperature (viscosity) of PP matrix, as well as heterogenic cellulose fibers translocations in the matrix.