EFFECTS OF CRYSTALLINITY AND SUPERMOLECULAR FORMATIONS ON THE INTERFACIAL SHEAR-STRENGTH AND ADHESION IN GF PP COMPOSITES

Aim of this study was to screen the morphological effects on the interfacial shear strength (taui in glass fibre (GF) reinforced isotactic polypropylene (iPP) model composites. Taui was determined by a modified single fibre pull-out technique. It was established that the relation between taui(5 - 6 MPa) and the yield stress of the iPP (sigmay almost-equal-to 30 MPa) is at about 1 : 6 and that the taui values were not influenced by the mophological superstructure set under isothermal crystallization conditions. Increased taui was only observed when specimens were produced non isothermally, by quenching (taui almost-equal-to 9 MPa). This improvement could not be related to thermal shrinkage stresses. The enhancement in taui was attributed to better wetting and improved adhesion due to the enlarged amorphous PP (aPP) - phase. A schematic adhesion model considering the wetting behaviour of aPP and iPP was proposed.