The influence of flame retardant filler on the mechanical, thermal, rheological and flame retardancy properties of silane crosslinked linear low density polyethylene/low density polyethylene blend nanocomposite

Abstract

AbstractLinear low density polyethylene (LLDPE) and low density polyethylene (LDPE) blend at 70/30 wt% ratio respectively was grafted and crosslinked with aluminum hydroxide (ATH) with and without the presence of montmorillonite (MMT) nanoclay using twin screw extruder. The effect of flame retardant ATH loading (5, 10, 15, 20 wt%), with and without the addition of MMT nanoclay, on the mechanical, thermal, rheological, flame retardancy and morphological properties has been studied and reported. The incorporation of ATH filler into crosslinked LLDPE/LDPE blend enhanced all the aforementioned properties; and it was found that increasing ATH content from zero to 20 wt% has improved tensile strength of the virgin LLDPE/LDPE blend by about 16 MPa. However, the addition of MMT nanoclay into the crosslinked LLDPE/LDPE blend with ATH filler, particularly at higher ATH loading (20 wt%), has not significantly increased the tensile strength. Thermogravimetric analysis (TGA) results have shown significant thermal stability improvement for virgin LLDPE/LDPE blend due to crosslinking, increased ATH filler loading, and subsequent addition of MMT nanoclay. However, at onset temperature, lower degradation rate was observed for samples containing higher ATH loading (15 and 20 wt%). At lower frequency region, it was found that the incorporation of higher ATH filler content and MMT nanoclay into crosslinked LLDPE/LDPE blend have increased the complex viscosity, storage modulus and loss modulus for virgin LLDPE/LDPE. The FTIR results have confirmed that silane crosslinking reaction of the virgin LLDPE/LDPE blend has occurred. The results obtained from flammability test, UL‐94 tests, showed that the flame retardancy of virgin LLDPE/LDPE blend has improved significantly due to the higher ATH filler loading, with and without the presence of MMT nanoclay filler. It was found that the higher ATH filler loading (20 wt%), addition of MMT nanoclay and subsequent crosslinking in the virgin LLDPE/LDPE blend have exhibited and achieved the best flame retardancy result for virgin LLDPE/LDPE blend. Furthermore, SEM results have also shown that improved flame retardancy for crosslinked LLDPE/LDPE blend samples containing a higher ATH loading and MMT nanoclay compared to virgin LLDPE/LDPE blend due to the formation of protective char layer on the surface, which finally enhanced flame retardancy properties of virgin LLDPE/LDPE blend.