Effect of nanoclay on combustion, mechanical and morphological properties of recycled high density polyethylene/marula seed cake/organo-modified montmorillonite nanocomposites

Composites based on recycled high density polyethylene (RHDPE), marula seed cake (MSC) and organo-modified montmorillonite (OMMT) were prepared by melt compounding. This paper targets to evaluate the potential for the utilization of RHDPE and underutilized MSC as material for the development of composites, as well as reinforcement effect of OMMT on them. In order to enhance the weak interfacial interaction between the hydrophilic MSC, hydrophobic RHDPE and OMMT, maleic anhydride-grafted polyethylene was used as a compatibilizer. The effects of (MSC, 0, 10, 20, 30, 40, 50 wt %) and (OMMT, 0, 2, 4%) on the combustion, mechanical and morphological properties were studied. Findings of this study show that both MSC and RHDPE can be used in the manufacture of composites. The MSC gave the optimum improvement of tensile and flexural strengths at 10 wt %, while tensile and flexural moduli increased with increasing MSC up to 50 wt %. The optimum improvement of mechanical properties was achieved at 2% OMMT. Increase in MSC loading reduced the heat release rate (HRR), mass loss rate (MLR), burning rate (BR) and limiting oxygen index (LOI), but dramatically increased the time to ignition (TTI) of the composites due to high lignin content which produced char. OMMT increased LOI and TTI but decreased HRR, MLR and BR. The higher the LOI is, the better the flame retardancy of the composite. Morphologies of the nanocomposites were analyzed by SEM and XRD, and the results showed increased d-spacing of clay layers indicating improved compatibility between RHDPE and clay and MSC.