EFFECT OF NUCLEATION, FILLER ANISOTROPY AND ORIENTATION ON THE PROPERTIES OF PP COMPOSITES

Polypropylene (pp) composites containing CaCO3 and talc were prepared and investigated as a function of composition. The effect of nucleatio n was studied by thermoanalytical methods, structure and particle orie ntation were investigated by electron spin resonance spectroscopy, lig ht and electron microscopies, while tensile and fracture tests were ca rried out to characterize mechanical properties. For both types of com posite, particle anisotropy and orientation have a more pronounced eff ect on properties than nucleation. Orientation of the anisotropic fill er particles occurs even under mild shearing conditions and its degree depends on the composition. In tension, the composition dependences o f the yield stress and tensile strength are determined by the decrease of effective load-bearing cross-section and interaction. In impact, c rack initiation plays an increased role, as does the reinforcing effec t of the filler. In failure of particulate-filled composites the main energy-consuming process is plastic deformation of the matrix, which i s modified by the presence of the filler. Dewetting increases, while i nterfacial interaction and formation of an interphase decrease, plasti c deformation and energy consumption.