High-density polyethylene/mollusk shell-waste composites: effects of particle size and coupling agent on morphology, mechanical and thermal properties

Composites based on high-density polyethylene (HDPE) and mollusk shell-waste (MSW) particles, with several concentrations and two different micro-sizes, were prepared by melt compounding and injection molding. The matrix flow behavior was not altered by the MSW incorporations. SEM analyses revealed weak filler/matrix interfacing and the presence of agglomerates (in the composites with higher particle concentrations). For the 2 wt% composites, good filler dispersion and distribution was observed in the HDPE matrix. The crystallinity of the matrix increased approximately 10% when adding lower MSW concentrations. For the composites with higher MSW concentrations and finer particles the thermal degradation temperature of HDPE (at a 20% mass loss) increased by approximately 26 °C. The tensile modulus increased by approximately 10% for the 2 wt% and 8 wt% composites with coarse particles. With lower MSW concentrations and finer particles, the flexural modulus increased by more than 37%. The composites modified with titanate presented properties similar to unmodified composites. Molecular interactions were verified by the presence of a band at 1030 cm−1, yet were not sufficient to promote improvements in the mechanical properties of the modified composites.