Mechanical properties and flammability of sisal/PP composites: Effect of flame retardant type and content

In this research, magnesium hydroxide (Mg(OH)2) and zinc borate, as flame retardants, were incorporated into sisal/PP composites. Maleic anhydride grafted polypropylene was also used as a compatibilizer. Adding flame retardants into sisal/PP composites reduced burning rate and increased thermal stability of the composites. No synergistic effect was observed when both magnesium hydroxide and zinc borate were incorporated in the sisal/PP composites. In addition, the sisal/PP composites exhibited insignificant difference of shear viscosity at high shear rate indicating that types of flame retardants used in this study had no impact on the processability of the composites. Good distribution of flame retardants and sisal fiber in PP matrix was also observed. All PP composites had lower impact strength than the neat PP. However, the sisal/PP composites with the addition of Mg(OH)2 and zinc borate exhibited comparable tensile and flexural properties to the sisal/PP composites without adding those flame retardants. Therefore, the addition of Mg(OH)2 and zinc borate enhanced flame retardancy of sisal/PP composites without sacrificing their mechanical properties.