Abstract: High-density polyethylene(PE-HD) was slightly cross-linked by various contents of dicumyl peroxide (DCP). The melt strength and crystallization behavior of the resultants were characterized by Rheotens and DSC. It is shown that low contents of DCP leads to the decrease of melt strength of the resultant, but increases their crystallization rates and crystallization degree; while the contents of DCP was 0.5 phr，the melt strength of the resultant reaches its highest value, 0.127 N, and lowest crystallization degree. The resultants were extrusion foamed by supercritical nitrogen, and the resultant foams were observed by SEM and a density meter. The results showed that while the contents of DCP was 0.5 phr, the PE -HD foam was endowed with the best cell morphology with the smallest cell size and lowest density of 0.5853 g/cm3.

Key words: high density polyethylene, dicumyl peroxide, supercritical fluid, extrusion foaming, melt strength, crystallization behavior, cell size, density