Modification of Polyethylene and Incorporation of Al(OH)3 for Improvement of Mechanical Properties, Burning Behaviour and Thermal Stability

In order to improve thermo-mechanical and flame-retardant properties of polyethylene, the polymer was cross-linked with vinyltriethoxysilane by using benzoyl peroxide as an initiator; and then various concentrations (0-35%) of aluminium hydroxide (ATH) were incorporated. The effect of curing was observed with respect to improvement in mechanical, thermal and burning properties. The three types of blends (unmodified PE, uncured silane-grafted PE and silane-cross-linked PE loaded with ATH) in the form of heat pressed sheets, were characterized for their mechanical properties like tensile strength and elongation-at-break. Solvent uptake, thermogravimetric analysis and burning behaviour of the blends were studied to determine the effect of increased filler concentration, thermal stability and time required for burning, respectively. It was observed that modification of polyethylene (PE) not only mitigates the reduction in these properties in simple polyethylene but actually enhances them by modification. In the case of simple PE, the incorporation of filler causes a marked deterioration in mechanical properties (elongation-at-break and tensile strength). However, approximately 20% increase in tensile strength and 50% control over the drastic decrease in elongation-at-break were observed for modified and filled polyethylene. The previously reported results show degradation of both these properties. In the proposed method, modification of polyethylene by silane crosslinking improves the burning time approximately 2.5 fold that of the same amount of filler. A clear difference in these properties for the incorporation of ATH to PE, uncured silane-grafted PE and silane cross-linked PE has been found. These properties follow the order of superiority as: silane cross-linked PE silane-grafted uncured PE physically filled PE. The influence of cross-linking and filler concentration on thermo-mechanical and burning properties due to efficient interaction of filler with PE, and that of silane cross-linked PE is discussed and analyzed.