Improvement of flame retardancy and thermal stability of highly loaded low density polyethylene/magnesium hydroxide composites

Abstract This study aims to enhance the flame retardant efficiency and thermal stability of low density polyethylene (LDPE) by using halogen‐free inorganic additives. To prepare the highly loaded flame retardant polymer composites, LDPE melt mixes with magnesium hydroxide and magnesium carbonate at different weight ratios using a twin‐screw extruder. The composites are characterized by thermogravimetric analysis, crystallinity degree, tensile strength, morphological analysis, limiting oxygen index and UL‐94 vertical burning test. An optimum MH/MC weight ratio of 60/40 provides satisfactory composite properties with increased maximum thermal degradation temperature from 472.3 to 483.5°C, the highest LOI value of 32.5% and a UL‐94 V‐0 rating without melt dripping. The homogeneity of this composite is improved by using a polymeric compatibilizer, MAH‐g‐PE and an enhancement in tensile strength, elongation at break and elastic modulus values of 33.68%, 33.02% and 23.55%, respectively, are obtained. In order to create synergism between the flame retardant additives, 1, 3 and 5 wt% zinc borate is added to the composite system. The incorporation of 5 wt% ZB causes a significant delay in the thermal decomposition of MH with an improvement of 51.8°C in maximum degradation temperature. This composite also exhibits a satisfactory flame retardant grade with a UL‐94 V‐0 rating.