Relationship between migration potential and structural parameters in crosslinked polyethylenes

Interactions between water and crosslinked polyethylenes (XPE) pipes are subject to regulatory control. In line with this, the objective of our work has been to identify some methods enabling to predict the behaviour of XPE vis à vis its contents. In our study, series of PEHD were crosslinked by β-irradiation at various crosslinking densities. With regard to the structural parameters measured for XPE, we were led to select the evaluation of crystallinity by DSC, the evaluation of crosslink density through its gel fraction and through dynamic mechanical analysis in the rubbery state. These properties are supposed to have a significant effect on the migration potential. With regard to the measurement of the migration potential, an organic solvent was used to accelerate the migration process and the quantity of migrating species was evaluated using gas chromatography. Our results show that irradiation increase the degree of crosslinking, which has the effect of reducing the potential of migration. It comes out of these conclusions that the measurement of structural characteristics of XPE may be a relevant way to predict their potential migration.