Polypropylene /montmorillonite nanocomposites prepared by the delamination of the filler

摘要

Polypropylene/montmo-rillonite (PP/MMT) nanocomposites were prepared by the exfoliation of the nanoclay during processing. The filler was used in various forms (sieved bentonite, sodium and organophillic MMT) in order to determine the effect of subsequent stages of organoclay preparation on the structure and properties of the composite. The filler content was varied over a relatively wide range to determine the extent of maximum reinforcement and the range of practically relevant compositions. Specimens were injection-molded with various weak sites (weld lines, gate section) in the test area to see the performance of the nanocom-posite under practically relevant conditions. The results proved that extensive exfoliation of the organo-philic MMT occurred during the homogenization and subsequent injection molding of the PP composites studied; however, organophilization of NaMMT was not complete, which hindered the perfect exfoliation of the MMT layers. Sieved bentonite and NaMMT behaved like traditional fillers, while the incorporation of the organoclay into PP yielded a true nanocomposite. Because of incomplete exfoliation and poor adhesion only a moderate improvement of mechanical properties was achieved in the study. Reinforcement depends on composition; above a certain filler content the nanoclay behaves like a particulate filler possibly owing to the stacking of exfoliated layers. The weld line strength of PP nanocomposites is very low; exfoliated clay particles orientate parallel to the weld line and strongly deteriorate the properties.