The effect of processing on the structure and properties of crosslinked closed cell polyethylene foams

This paper analyses the relationships between production, structure and properties of a collection of crosslinked closed cell polyethylene foams. Foams with similar densities produced from a similar base polymer and manufactured using three different technologies (high pressure nitrogen solution process, compression moulding and semicontinuous processing) have been characterised. On the one hand, several foam characteristics such as density, cell diameter, cell wall thickness, cell shape, fraction of mass in the edges, gel content, crystallinity and melting temperature have been measured and related to the way in which the foams were produced. On the other hand, three important physical properties such as thermal conductivity, Young's modulus and thermal expansion have been measured analysing the experimental results in terms of the previously cited foam characteristics. The results have shown that the production route used to manufacture the foam strongly influences the foam structure and as a consequence the main physical properties.