Dynamic Mechanical Properties of Grafted Polypropylene Composites Reinforced with Acetylated Wheat Straw Fibers

Abstract

Dynamic mechanical properties of polypropylene (PP) and grafted polypropylene (PP-g-MA) composites reinforced with acetylated wheat straw fibers (WSF) is reported in this work. The materials were prepared with different fiber particle sizes (40, 80 and 140 U.S. mesh) and at different fiber contents (5, 10 and 15 wt.%). The PP and PP-g-MA composites, where anhydride maleic (MA) was used as coupling agent, were obtained using a twin-screw extruder; whereas an injection-molding machine molded the composite pellets into testing specimens. To observe the morphology of the composites, micrographs were taken with an optical microscope. The Dynamic mechanical properties were analyzed using a torsional rheometer. The morphological analysis showed a high porous structure somehow similar to foamed materials. The storage modulus (G') increased by increasing the fiber content, and decreased with fiber particle sizes for the PP composites. Meanwhile, the use of the coupling agent additive promoted a modulus increase due to higher fiber-polymer interaction, from better adhesion and chemical bonds formation between the fibers-coupling agent-PP.