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Evaluating the influence of coupling agents in the structural properties of polypropylene coconut fiber composites

Coupling agents have been widely used to improve the adhesion of composites reinforced with vegetable fibers. In this study, the influence of three different coupling agents was analyzed: polyethylene and polypropylene both grafted with maleic anhydride and titanate grafted in polyethylene. The composites with 30 wt% percentage of coconut fibers and 6 wt% of compatibilizers were processed in a co-rotating twin-screw extruder. Specimens were submitted to mechanical and thermal treatments to evaluate these properties. Data showed that coupling agents significantly influence composite properties. Polypropylene-based coupling agent shown good results to the composites increased the yield strength by 23% and the tensile strength by 32% with respect to the polymer matrix. These results represented thus an adequate and positive effect of the coupling agents related to the more relevant mechanical properties to manufacture structural composites using vegetable fibers. Based on results achieved in this investigation, the composite containing coconut fiber presented the optimum set of mechanical properties and improved thermal stability, which make it suitable for applications such as structural components.