Analysis of the foaming mechanisms of materials based on high-density polyethylene (HDPE) crosslinked with different irradiation doses

Different crosslinked high-density polyethylene based cellular polymers have been produced by a free foaming process using a chemical blowing agent. The polymer matrix was crosslinked by electron beam irradiation using different doses ranging from 25 to 175 kGy. The main aim of this work is to study the effect of the different irradiation doses on the density, cellular structure, and foaming mechanisms. Results show that irradiation doses as high as 175 kGy have to be used to obtain cellular materials with a low relative density (0.06), cell sizes of around 50 m, and cell densities of 1.6 x 10(7) cellscm(-3). The strain hardening of the polymer matrix increases with the irradiation dose leading to an increase of the polymer resistance to be stretched, which helps to avoid undesirable cellular degeneration processes. Irradiation doses lower than 175 kGy are not able to stabilize the cellular structure leading to foams with relative densities higher than 0.1 and degenerated cellular structures. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46276.