Impact fracture study of multicomponent polypropylene composites

Abstract

Standard impact resistance and fracture mechanics characteristics of 17 three-component PP/BaSO 4/elastomer composites and reference compounds were determined as a function of composition, dispersed phase structure and particle size of the filler. The results showed that the effect of structure is very similar on all characteristics and it influences also the temperature dependence of impact resistance. Structure was controlled by the application of functionalized polymers. The extent of encapsulation of the filler particles was estimated by calculations using the Lewis–Nielsen model and comparing calculated and measured moduli. Impact resistance increased with higher degree of encapsulation, but the crucial factor determining toughness was the prevailing micromechanical deformation process and the deforming volume. Separate distribution of the components and weak adhesion of the filler to the matrix lead to a better impact resistance than does significant encapsulation. The results prove that while stiffness of these multicomponent systems is basically determined by the extent of embedding, the correlation of toughness and structure is much more complex. The dominating role of micromechanical processes and the numerous factors influencing them (adhesion, embedding, particle size, elastomer properties, etc.) explain the contradictory results published in the literature.