Composites with ß-Polypropylene Matrix: The Effect of Filler on Resulting Structure and Properties
Jiri Kotek, Ivan Kelnar, Josef Baldrian
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic
Czech Republic

Keywords: beta-polypropylene, composite, properties

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Isotactic polypropylene is a polymorphic material, which can crystallize in three different crystalline phases, namely monoclinic (alpha), hexagonal (beta) and triclinic (gamma). Commercial grades of PP crystallize into the alpha-phase, but in some cases this can be accompanied by a lower amount of hexagonal beta-phase. It has been shown that the toughness of the ß-phase isotactic polypropylene is considerably higher than that of the alpha-phase. Since the formation of the ß-phase can be promoted by adding suitable nucleating agents at concentrations lower than 0.1 wt.%, the more tough ß-PP is of considerable scientific and commercial interest.

In the present work, the possibilities of the preparation of filled ß-PP composites are studied. The goal was to check whether the higher ductility of ß-polypropylene can compensate the well-known detrimental effect of the filler on the failure behaviour. Filled materials, similar to those based on conventional alpha-polypropylene were prepared. Several fillers were chosen: CaCO3, Mg(OH)2, glass fibers and natural fillers, such as wood flour, starch and cellulose fibers. In order to assess the effect of ß-PP matrix properties on mechanical properties of the composite, analogous materials with the alpha-PP matrix were prepared. The effects of the addition of selected fillers on morphology, ß-phase content and resulting mechanical properties are reported.