Abstract
AbstractCrosslinked polyethylenes (PEX) with different degrees of crosslinking were separated in sol and gel fractions by extractions with hot o‐dichlorobenzene. The distribution of branches was determined by 13C NMR‐spectroscopy, according to the method of Randall et al. The relative amounts of butyl branches decrease in the gel fraction and increase in the sol fraction with increasing degree of crosslinking. For the other branches the changes were small or not observable. In addition, the activation energies for a sol and a gel fraction were determined by measurements of the spin‐lattice relaxation times T1 at temperatures between 303 and 403 K. The activation energy was higher for the gel fraction, suggesting a restricted motion of the polymer segments in the gel.
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