Effects of ammonium polyphosphate content on mechanical, thermal and flammability properties of kenaf/polypropylene and rice husk/polypropylene composites

This study investigated the effects of ammonium polyphosphate (APP) content on the mechanical, thermal and flammability properties of kenaf/polypropylene (KF/PP) and rice husk/polypropylene (RH/PP) composites prepared by melt mixing technique. Polyethyleneoctene grafted maleic anhydride (POE-g-MAH) has been used as compatibilizer. The PP/KF/APP and PP/RH/APP composites were investigated using flexural and impact tests, scanning electron microscope, thermogravimetric analysis (TGA), differential scanning calorimeter and limiting oxygen index (LOI) test. Flexural modulus of PP/KF/APP and PP/RH/APP composites significantly improved from approximately 1.1–2.5 and 0.9–2.1 GPa, respectively, by the addition of 10 phr APP. The flexural strength of the composites also increased by the incorporation of 10 phr APP. In addition, the impact strength of the PP/RH/APP composites increased above 10 phr APP content. From the TGA results, incorporation of APP into PP/RH and PP/KF composites increased the char residue and thermal stability of the composites. Furthermore, the addition of APP increased the flame retardancy of the PP/KF/APP and PP/RH/APP composites with a significant increase of LOI at 10 phr.