SANTOS, Z. I. G.; SANTOS, Zora Ionara Gama dos.
Resumo:
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.
