Diffusion mechanism of byproducts resulting from the peroxide crosslinking of polyethylene

In this study, a polyethylene grade used for applications in the insulation of energy cables was crosslinked by the peroxide crosslinking route. The impact of dicumyl peroxide (DCP) crosslinking on the polymer microstructure was studied. The different byproducts formed during the crosslinking reaction [acetophenone, a-cumyl alcohol, and a-methyl styrene (aMS)] were identified and quantified. Another molecule, 2,4-diphenyl-4-methyl-1-pentene, regarded as an aMS dimer, was detected for the first time. Some amounts of residual DCP were also detected. A detailed study of the diffusion mechanism of each byproduct under different desorption conditions (e.g., samples exposed to vacuum or atmospheric conditions) and temperatures was performed. The diffusion coefficient values were determined and are discussed as a function of the desorption conditions and byproduct characteristics. Through this study, essential diffusion parameters were provided as a first step for further modeling development to allow the definition of optimized desorption conditions for a large range of sample geometries and thicknesses. (C) 2016 Wiley Periodicals, Inc.