Methods and benefits of crosslinking polyolefins for industrial applications

Abstract

The silane grafting route to the crosslinking of polyolefins can open up wide areas of application not easily attained by the conventional techniques of peroxide addition or irradiation. The thermal limitations on processing and cure rates imposed by the former; and the high capital cost, thickness and shape limitations imposed by the latter are dispelled when a two step grafted system is employed. The technology involves the chemical grafting of an easily hydrolysable vinyl silane onto a polyolefin chain, crosslinking being achieved by post-hydrolysis condensation to yield a siloxane linkage. The technique can be applied to aliphatic polymers and copolymers ranging in stiffness from HDPE to EPR. As well as property improvements in creep, environmental stress cracking resistance, impact, chemical and crack growth resistance; the materials retain a useful strength and exhibit resistance to flow and irreversible distortion above the crystalline transition temperature (where applicable). The years of experience accrued by AEI in the formulation, manufacture and handling of silane grafted materials is now resulting in the production and development of a wide range of specialised high performance materials. This paper outlines property levels attainable with specific reference to well established as well as developing areas of application. A wide range of products is covered including electrical cable insulation, hot water pipe, adhesives, floorings, foams, heat shrink products and packaging; the application of crosslinking to all of which can be seen to be facilitated by the grafted silane route and more specifically by the thermoplastic processability afforded by this route.