PARTICLE BREAK-UP AND COALESCENCE IN HETEROGENEOUS PP/EPDM BLENDS - EFFECT OF PARTICLE-SIZE ON SOME MECHANICAL-PROPERTIES

Heterogeneous blends of polypropylene and ethylene-propylene-diene elastomer were prepared in an internal mixer. Homogenization time was varied between 2.5 and 40 min and the resulting particle size of the dispersed elastomer phase was determined. It was established that particle size changes continuously during homogenization. Particle break-up, coalescence and occasional degradation together determine the actual particle size. Shear conditions (τ, γ) and relative viscosity of the polymers are the most important factors which influence the equilibrium particle size. A semi-empirical treatment of the experimental data yielded a good correlation between these parameters and the particle size. Correlations have been found between the particle size and some tensile properties of the samples proving that particle size influences the deformation and failure processes in the blends.