Avaliação do mecanismo de fratura dos compósitos de polipropileno/talco através do método EWF (Trabalho Essencial de Fratura)

Abstract

The use of talco as a dispersive phase in thermoplastic composites has strategic and economic functions in the polymer industry, propitiating advances in properties such as rigidity, thermal and dimensional stability, amongst others; seeing that this mineral filler presents a lamellar geometry. The objective of the present dissertation was to evaluate the effect of varied amounts of talco on the fracture mechanisms of polypropylene/talco composites applying the EWF method (Essential Work of Fracture). Composites of 5, 10 & 15 wt% of talco were prepared by extrusion then injected into mold plates, subsequently, the specimens were cut in DDENT geometry (deeply double edge-notched type). Six varied ligament lengths of 6 to 16mm were prepared for evaluation. The data used to determine the EWF parameters were obtained by unidirectional tensile tests. The results show that the specific essential work fracture (we) of the composites was considerably lower than that of the pure polypropylene specimen, which indicates that talco produced modifications in the composite’s structure, reducing the capacity to absorb energy. An increment in the specific nonessential work fracture (βwp) was observed with increasing amounts of talco, due to structural alterations which raise the amount of energy needed for plastic zone deformation. Based on the results of this study, the EWF method proves efficient in the fracture tenacity evaluation of these composites.