FRACTURE PROPAGATION IN PARTICULATE-FILLED POLYPROPYLENE COMPOSITES .3. INFLUENCE OF MICA SURFACE TREATMENTS

Composites of isotactic polypropylene and fixed weight (40%) of mica without and with different surface treatments (isopropyl triisostearoyl titanate (TTS) and 3-aminopropyl triethoxy silane) were prepared by injection moulding. The influence of surface treatment on the microstructure and fracture propagation in the composites was investigated. Microstructural investigations revealed that the surface treatments influenced the mica flake orientation, which in turn resulted in the changing of the skin-core zone thickness. The influence of the mica surface treatment was found to be insignificant at -30° C whereas at 25 and 80° C the surface treatments considerably influenced the fracture propagation. The normalized modulus and the fracture toughness (Kc) of the composites were found to vary with mica surface treatments. Interfacial bonding was also found to vary with surface treatment. Schematic models for crack propagation in PP-mica composites are proposed. © 1990 Chapman and Hall Ltd.