Improving the extensional rheological properties and foamability of high-density polyethylene by means of chemical crosslinking

Obtaining high-density polyethylene-based microcellular foams is a topic of interest due to the synergistic properties that can be obtained by the fact of achieving a microcellular structure using a polymer with a high number of interesting properties. However, due to the high crystallinity of this polymer, the production of low-density microcellular foams, by a physical foaming process, is not a simple task. In this work, the proposed solution to produce these materials is based on using crosslinked high-density polyethylenes. By crosslinking the polymer matrix, it is possible to increase the amount of gas available for foaming and also to improve the extensional rheological properties. In addition, the foaming time and the foaming temperature have also been modified with the aim of analyzing and understanding the mechanisms taking place during the foaming process to finally obtain cellular materials with low densities and improved cellular structures. The results indicate that cellular materials with relative densities of 0.37 and with cell sizes of approximately 2 mu m can be produced from crosslinked high-density polyethylene using the appropriate crosslinking degree and foaming parameters.