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.

Enhanced flame retardancy and thermal stability of zinc borate and magnesium carbonate as a promising alternative for Sb2O3 toward polyvinyl chloride

“…The highly flameretardant efficiency of zinc compounds like ZC and ZB for flexible PVC was attributed to the fact that the highly efficient flame-retardancy effect of ZC and ZB mainly occurred in the early stage of flame burning. 9 As displayed in Figure 1, ZC and ZB broke down into zinc oxide (ZnO) at temperatures of roughly 220 C and 290 C, 9,22,27 respectively, which could react with HCl decomposed from flexible PVC to give ZnCl 2 . As a kind of strong Lewis acid, ZnCl 2 could further accelerate the dehydrochlorination of flexible PVC to go on the generation of conjugated polyene structures, leading to the formation of carbon residues under high temperatures.…”

Self‐emulsification synthesis of epoxy phosphate ester and its flame‐retardant mechanism in flexible poly(vinyl chloride)/magnesium hydroxide composites

“…Different mechanisms, such as free-radical trapping and catalytic charring effect, are involved in the synergistic flame retardancy. The addition of aluminum hydroxide 48 or magnesium carbonate 49 to MH can also demonstrate a strong synergistic flame-retardant effect because of their varying decomposition temperatures.…”

Synthesis of Zinc Oxide Doped Magnesium Hydrate and Its Effect on the Flame Retardant and Mechanical Properties of Polypropylene

“…The flame retardant efficiency of MH is ingeniously improved via the introduction of different flame retardant mechanisms, such as free radical trapping and the catalytic charring effect. Adding aluminum hydroxide [29] or magnesium carbonate [30] with MH can also show a considerable synergistic flame retardant effect, which is ascribed to the different decomposition temperatures.…”