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 nucleation was studied by thermoanalytical methods, structure and particle orientation were investigated by electron spin resonance spectroscopy, light and electron microscopies, while tensile and fracture tests were carried out to characterize mechanical properties. For both types of composite, particle anisotropy and orientation have a more pronounced effect on properties than nucleation. Orientation of the anisotropic filler particles occurs even under mild shearing conditions and its degree depends on the composition. In tension, the composition dependences of the yield stress and tensile strength are determined by the decrease of effective load-bearing cross-section and interaction. In impact, crack initiation plays an increased role, as does the reinforcing effect of the filler. In failure of particulate-filled composites the main energy-consuming process is plastic deformation of the matrix, which is modified by the presence of the filler. Dewetting increases, while interfacial interaction and formation of an interphase decrease, plastic deformation and energy consumption.