Mechanical behaviors and flammability of perlite filled recycled high-density polyethylene composites

Recycled high density polyethylene (rHDPE) has found increasing use in various applications due to its low cost and abundant availability. However, it possesses low mechanical properties and inferior flame resistance. This work uses the approach of adding a low-cost additive (perlite) into the rHDPE to improve those properties and studies the mechanical behaviors and fire resistance of the perlite filled rHDPE composites while still maintaining low cost. Composites with different ratios of perlite to rHDPE (neat rHDPE, 1:10 perlite/rHDPE ratio; and 2:10 perlite/rHDPE ratio) were produced through twin extrusion process and compression molding processes. The composites were tested in their performance in tension and flexure as well as flame resistance. The testing results showed that the tensile modulus increased from 0.89 (neat rHDPE) to 1.14 GPa (composite with 2:10 perlite/rHDPE ratio), while the tensile strength showed a slight increase as well. The flexural modulus of the composite increased by approximately 37.5% with the addition of perlite. However, the impact resistance decreases with increasing perlite amount added in the rHDPE. Finally, the flame resistance was found to increase by around 20% with the incorporation of perlite. These findings suggest that perlite is a promising cost-effective additive material for enhancing the tensile and flexural properties and flame retardancy of rHDPE.