Effect of modified nanofillers on fire retarded high-density polyethylene/wood composites

Abstract

In this study fire retarded HDPE/WF composites based on high density polyethylene (HDPE) and wood flour (WF) were investigated. Polymer and WF ratio was kept at 70/30 while concentration of fire retardant was 20 mass %. Ammonium polyphosphate and aluminum hydroxide were used as fire retardants. To diminish the influence of high loadings of fire retardants on mechanical properties two different types of organically modified nanofillers (CaCO3 and SiO2) were used. Surface modification of HDPE polymer and nanofiller was done to enhance the compatibility in composite and improve the mechanical properties and fire performance. Mechanical properties were characterized by dynamic mechanical analysis while compatibility of components in composites was followed through morphology by scanning electron microscopy. Thermal and fire properties were characterized by thermogravimetric analysis, pyrolysis combustion flow calorimetry, and limiting oxygen index. The obtained results show that addition of surface modified nanofiller considerably affects the morphology resulting in the enhancement of mechanical and fire properties. Ammonium polyphosphate fire retardant in combination with SiO2 nanofiller showed the highest limiting oxygen index value, the lowest heat release rate, and total heat released in pyrolysis-combustion flow calorimetry test indicating best overall fire performance.