Estudo do comportamento de fratura em compósitos polímero/madeira (WPC'S) através do método EWF.

Abstract

Mechanical properties and fracture behavior of heterophasic polypropylene (PP) and PP composites with wood particles were studied by the Essential Work of Fracture (EWF) method. All formulations, with and without coupling agent containing 0, 5, 15 and 25% wood particles were prepared by twin screw extrusion; and the specimens type DENT were injection molded. The data used to determine the EWF parameter's were obtained from tensile test. Firstly, it was verified the validity of EWF method for PP matrix. The influence of wood particle content, coupling agent, sample thickness and accelerated aging on the EWF parameters was studied. The results show that it is possible to use the EWF method to evaluate the fracture behavior of pure polypropylene and its composites with and without a coupling agent. Results also show that specific essential work of fracture, we, of the composites was significantly smaller than that pure PP, and plastic energy dissipation, (3wp decreased markedly with increasing content particle. It was concluded that the coupling agent promoted an increase in the we value and a decrease in the specific non-essential work of fracture (fiwp). The effects of thickness on EWF parameters was more pronounced on essential work of fracture (we ) parameter, while non-essential specific work of fracture (/3wp) was. It was also shown that non valid values of EWF parameter were observed for aged samples, showing great edge effect and transition from plane stress to plane strain. It was observed that photodegradation process of the PP matrix was accelerated by the presence of the wood particles.