Quantitative determination of short branches in high‐pressure polyethylene by gamma radiolysis

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Abstract
A careful study of the radiolysis products of a series of ethylene α‐olefin copolymers and ethylene homopolymers has shown that if a correction is applied, to take into account the fragments arising from scission at chain ends, the remaining products can be quantitatively accounted for as entirely due to scission of side branches introduced onto the backbone chain by the α‐olefin comonomer. The cleavage of branches takes place, for all practical purposes, exclusively at the branch points at which the branches are attached to the backbone chain. The same data together with similar radiolysis data of poly(3‐methyl pentene‐1) and poly(4‐methyl pentene‐1) have further shown that all branches cleave with equal efficiency, regardless of their length. Radiolysis does, therefore, provide a reliable and convenient tool for the quantitative characterization of high‐pressure polyethylene with regard to the unique short‐chain branching distribution that is characteristic of each.