Abstract
Sandwich panels, polyurethane foam sandwiched between two sheets of steel, form the walls and roofs in the construction of buildings. ArcelorMittal is a manufacturer of the steel as well as these finished panels. For this project they combined with a supplier of the polyurethane foams, Huntsman Polyurethanes, to joint-fund a research project investigating the fundamental mechanisms of adhesion, as well as the causes of failures in the product which manifests primarily in two different ways, blisters appearing on the outer surfaces of the panels in use and voids appearing in the foam during fabrication. There is a fundamental lack of understanding on how precisely these systems adhere together and thus what causes failures in the product, both during construction and also in use. In order to achieve these goals, characteristics of each of the constituent parts were evaluated; supporting, disputing and contributing entirely novel findings to the information available in literature. Following this the manufacturing processes were investigated thoroughly, examining each with reference to the locations of noted failure. The polyurethane foam/coated steel interface was found to be of specific interest. The nanoscopic mechanisms of adhesion through this interface were examined thoroughly using a variety of spectroscopic and imaging techniques. It was found that a number of components in the foam diffused into the polymeric coating. The diffusion was experimentally analysed to understand its role in the overall performance of the product. Finally, forensic analyses were conducted on a failed product displaying the blistering. Using the knowledge gained through the project this failure could be explained, contributing towards making a significantly enhanced product and thus potentially saving the sponsoring companies millions of pounds.