Effects of repetitive processing,wood content,and coupling agent on the mechanical,thermal, and water absorption properties of wood/polypropylene green composites

In an effort to determine to what extent natural fiber/plastic composites were recyclable, this study conducted repetitive processing cycles on wood flour/polypropylene composites through extrusion up to three times followed by injection molding. Mechanical properties of the composites, containing 10–50?wt% wood flour and with/without addition of 3?wt% maleic anhydride polypropylene (MAPP) as coupling agent, were evaluated by conducting tensile test, thermal analysis, and water absorption test. Repetitive processing as well as wood content and coupling agent addition influenced physical properties of the composites. MAPP functioned well in improving fiber-matrix adhesion in terms of mechanical properties. Repetitive processing did not deteriorate the composite’s properties; rather opposite effect was shown. Thermal analysis indicated that the alteration in properties was contributed by the molecular condition of the polypropylene matrix. Water absorption increased with the wood flour content but reduced when MAPP was added and with more processing cycles.