Simultaneous optimization of the mechanical properties of postconsumer natural fiber/plastic composites: Phase compatibilization and quality/cost ratio

In this work, a simultaneous optimization by phase compatibilization of four mechanical proprieties (flexural and tensile moduli, impact strength, and tensile stress at yield) of natural fiber/plastic composites was performed with respect to raw materials cost. In particular, a recycled resin of postconsumer origin (blend of high density polyethylene and polypropylene) with flax fibers was extruded with an additives package: a coupling agent (maleic anhydride grafted polypropylene) and an impact modifier (maleic anhydride grafted ethylene octene metallocene copolymer) to improve the interface between each phase. Then, the compounds were injection molded and tested. The analysis was performed according to a Box‐Behnken experimental design to study the effect of fiber concentration, total additives concentration, and impact modifier fraction in the additives package. The optimization process required three steps: to model the relationships between mechanical properties and selected factors by a multiple linear regression analysis, to identify the potentially optimum conditions using the desirability function approach (Derringer–Suich and Ch'ng et al.), and to determine the best composite composition (optimum condition) by a comparative analysis of the material quality/cost ratios. POLYM. COMPOS., 35:730–746, 2014.