Simultaneous effects of coupling agent and flame retardant on empty fruit bunch fiber/polypropylene composites

Oil palm empty fruit bunch fibers were treated in sodium hydroxide solution, and then composites were produced by 0–50 wt% untreated and treated empty fruit bunch fibers with polypropylene using a twin-screw extruder followed by an injection molding machine. To improve the interfacial adhesion in and flame retardancy of the composites, malic anhydride grafted polypropylene and magnesium hydroxide were also used in the formulation as a coupling agent and a flame retardant, respectively. Composites were characterized by tensile, flexural, impact and burning tests as well as by scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analyses. Tensile strength and flexural modulus of treated empty fruit bunch fibers–composite with malic anhydride grafted polypropylene and flame retardant are observed to increase by 23 and 133% more than the corresponding composite without these additives. Addition of malic anhydride grafted polypropylene considerably improves the mechanical strengths and thermal stability of the treated empty fruit bunch fibers- and untreated empty fruit bunch fibers-based composites from their respective uncoupled composites. Inclusion of flame retardant decreases the burning rate of the composites by about 60%. All these findings are attributed to the improved fibers-matrix interfacial adhesion by incorporation of malic anhydride grafted polypropylene and flame retardant, as demonstrated by scanning electron microscopy and Fourier transform infrared spectroscopy. Due to high burning resistance, the resulting composites can be proposed to apply in structural components and electrical appliances.