Polyethylene-based Composites with a Three-Component Inorganic Flame Retardant - Effect of a Different Component Ratio on Dielectric and Mechanical Properties

Abstract

The polymer composites based on polyethylene (PE) with particulate filler enhancing flame retardancy are increasingly used in producing cable insulation layers, even the most electrically stressed core insulation. This study evaluates the effect of flame retardants based on the commonly used aluminium hydroxide (ATH), magnesium hydroxide (MDH), and still less common but promising clay mineral called halloysite nanotubes (HNT) on the dielectric and mechanical properties of the PE composites designed primarily for the cable core insulation. The aim of the production of composites with mentioned fillers is to improve flame retardancy and to affect the dielectric and mechanical properties as little as possible compared to the neat PE by varying the proportions of fillers. Based on previous research, the total weight proportion of fillers in PE has always been 5%. Specifically, this study evaluates the effects of four different filler ratios on selected dielectric characteristics (relative permittivity, dissipation factor, dielectric strength, and volume resistivity) and the results of tensile tests. The results indicate an increase in dissipation factor with adding the filler, particularly with the combination of ATH:MDH:HNT in a 1:1:3 ratio. The dielectric strength remained consistent, except for the ratio of 3:1:1, which showed improvement. The mechanical properties were minimally affected, with the ratio of 1:1:3 exhibiting notable changes. The optimisation of the ratio of fillers incorporated primarily in terms of their fire retardancy of PE is also not negligible concerning dielectric and mechanical properties.