Study on the foaming of crosslinked polyethylene

The processing of crosslinked polyethylene foam, which has a closed-cell structure, has been investigated. In this study, two types of linear low-density polyethylene (LL) produced by a metallocene catalyst were crosslinked by dicumyl peroxide (DCP). The expansion ratio of the foams decreases with increasing the DCP content, which is due to the enhancement of the elastic modulus. Moreover, the crystallization temperature Tc of the foams is also responsible for the expansion ratio. After expansion, the crosslinked foam with lower Tc shrinks to a great degree prior to the crystallization, which is attributed to the volume reduction of the gas in the cells. As a result, the expansion ratio decreases. The degree of shrinkage decreases with increasing the Tc, because immediate crystallization prevents the shrinkage.