Impact fracture behavior of PP/ash composites with different coupling agents

ESTEBAN IGARZA; VALERIA PETTARIN; L. BARRAL LOSADA; MARIA JOSE ABAD; CELINA BERNAL; SANTIAGO GARCÍA PARDO

Les Diablerets

Conferencia; 5th International Conference on Fracture of Polymers, Composites and Adhesives - 5th ESIS TC4 Conference; 2008

In the present work, the impact fracture behavior of polypropylene (PP) reinforced with fly ash derived from the biomass combustion was investigated. Different coupling agents (a silane type coupling agent and maleic anhydride grafted polypropylene (MAPP)) were used in the composites formulation in order to change the compatibility between PP and ash. The effect of the ash content on the fracture properties was also analyzed. Instrumented impact tests were performed on SENB specimens obtained from compression-molding plaques in three-point bending using a ?falling weight? type machine at 1 m/s. In-plane fracture behavior was studied for all composites through the critical energy release rate (GIC). In the case of the composites with silane-treated ash, out-of-plane fracture properties were also studied through biaxial impact tests performed on disk shaped samples. It was observed that GIC values displayed a maximum with ash content irrespectively of the coupling agent used, suggesting that two competitive mechanisms were acting. The incorporation of both coupling agents (silane type or maleic anhydride grafted polypropylene) in the composites formulation led to a detrimental effect on the impact fracture properties. In contrast, the results obtained from biaxial impact tests showed a slight increase in the fracture energy with the incorporation of silane treated ash. Furthermore, SEM fracture surface observations revealed that ash particles debonded from the PP matrix due to the relatively poor interfacial adhesion between both phases. However, PP/MAPP/ash composites exhibited improved interfacial adhesion. Furthermore, the polymer matrix was unable to develop plastic yielding at the high strain rates developed under impact. Further work is in progress in order to elucidate acting deformation mechanisms by means of low blow tests.