A detailed investigation was carried out on the foaming of cross-linked low-density polyethylene (x-LDPE) sheets with CO2 as a blowing agent on a batch scale. The x-LDPE sheets were produced through two different sequences, i.e., part formation after irradiation (Sequence A), and irradiation after part formation (Sequence B). The foaming behavior of x-LDPE samples prepared by both Sequence A and B was compared in terms of cell size distribution, cell size, cell density and volume expansion ratio. The optimum radiation dose for the foaming of x-LDPE was found to be 50 kGy. At a foaming temperature of 100 degrees C, the cell size of x-LDPE foam was less than 10 mu m, and the maximal value of cell density reached 10(11) cells/cm(3). The SA and SB series of x-LDPE foams both had a microcellular structure. It may be possible to realize a continuous manufacture process for x-LDPE foam with the Sequence A. (C) 2008 Elsevier B.V. All rights reserved.