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Usability of three boron compounds for enhancement of flame retardancy in polyethylene-based cable insulation materials

2014-03-01
İBİBİKCAN, Esin
Kaynak, Cevdet
It is known that for the production of halogen-free cable insulation materials based on polyethylene, very high amounts of traditional metal hydroxide flame retardants such as 65 wt% aluminum hydroxide are required to fulfill international directives. In this respect, the aim of this study was to reveal possible enhancement effects of three boron compounds on the flame retardancy of two cable insulation materials: low-density polyethylene and its blend with ethylene vinyl acetate both loaded with aluminum hydroxide. For this purpose, a certain fraction of aluminum hydroxide was replaced with various amounts of zinc borate, boron oxide, and boric acid. The materials were compounded by the melt mixing method with a twin-screw extruder, while specimens were shaped by compression and injection molding. Limiting oxygen index, UL-94 vertical burning and mass loss cone calorimeter analyses indicated that replacement of certain amount of aluminum hydroxide with boron compounds could lead to certain levels of enhancement in many flame retardancy parameters. Residue analyses revealed that these improvements were basically due to further contribution of boron compounds to the physical barrier mechanism of aluminum hydroxide in both gas and condensed phases.