Crosslinked, heat shrinkable polypropylene compositions

Abstract

A heat-shrinkable article suitable for use as an insulating or coating material comprises a crosslinked composition of a polypropylene homopolymer or copolymer and an ethylene-propylene elastomer. The article is formed by a process comprising: i) creating a blend of the polypropylene homopolymer or copolymer and the ethylene-propylene elastomer by melt mixing; ii) melt processing the blend produced in i) to produce a melt processed material; iii) crosslinking the melt processed material produced in ii) by exposing it to radiation to produce a crosslinked material; iv) stretching the crosslinked material at a first temperature close to or above its softening or melting point and subsequently cooling it to a second temperature below its softening or melting point, to thereby freeze the crosslinked material in its stretched form. Subsequent heating of the article close to or above its softening point or crystalline melting point results in recovery of the pre-stretched dimensions of the article. Due to its relatively high content of polypropylene, the heat-shrinkable article thus produced has greater toughness and rigidity than polyethylene-based systems, making it suitable for use as insulation for wires and cables a heat-shrinkable corrosion resistant sleeves for high-temperature transmission pipeline joints, and for heat-shrinkable tubing or shapes for electrical insulation and mechanical protection.