On the use of fracture tests to assess the morphology-performance relationship of injected polypropylene blends and composites

MARIA ALEJANDRA COSTANTINO; CAREN ROSALES; VALERIA PETTARIN; CELINA BERNAL

Buenos Aires

Workshop; Workshop on Deformation and Failure of Polymer and Composites; 2018

When dealing with semicrystalline polymers such as polyolefins, morphology is an important feature since it greatly affects thermal and mechanical performance of processed parts. Many thermoplastic-composites are processed by an injection molding process, and the morphology of melt-crystallized polymers is known to be related to the fabrication technique. In composites and blends, morphology depends on factors such as the affinity and compatibility of the filler with the matrix, the matrix viscosity and the applied thermo-mechanical level, which depends on the processing conditions. The understanding of the fracture, microvoide formation and mechanics of composites and blends is crucial for engineers. In this work, the relationship between processing and performance is reviewed for different injected polypropylene pieces: polypropylene/clay nanocomposites, polypropylene/aluminum flakes microcomposites, and polypropylene/polyethylene blends. Mechanical performance of pieces was evaluated by means of quasi-static fracture tests. The effects of the molding process and of the filler on the microstructure and fracture properties of the polymer composites are reported. Also, the effect of the occurrence of in-homogeneities, such as weld lines or flow lines is summarized. Results arisen from fracture tests, both qualitative and quantitative, were proven to be a very efficient tool to evaluate the performance of this type of pieces.