Experimental Investigation of the Influence of the Compounding Process and the Composite Composition on the Mechanical Properties of a Short Flax Fiber-Reinforced Polypropylene Composite

Polypropylene (PP) composites containing 20 wt% short flax fibers are prepared, and the process parameters such as throughput, rotational speed, and screw configuration are varied during melt compounding with a corotating intermeshing twin-screw extruder. The investigations reveal that low rotational speeds, high throughputs, and moderate shear energy inputs by the screw configuration led to an optimum set of mechanical properties. To investigate the influence of different composite compositions on the mechanical properties, composites with fiber contents between 0 and 40 wt% and maleic anhydride-grafted PP (PP-g-MA) contents between 0 and 7 wt% are prepared. Increasing fiber contents enhance the Young's modulus and decrease the elongation at break and the notched impact strength. The tensile strength is barely affected. The addition of PP-g-MA increases the tensile strength as well as the elongation at break, whereas the Young's modulus is not influenced. Thus, PP-g-MA enhances the adhesion between PP and flax fibers significantly. (C) 2014 Society of Plastics Engineers