Polystyrene foams. I. Processing-structure relationships

In this study, processing-structure relationships in expanded polystyrene (EPS) made using near-critical carbon dioxide as a physical blowing agent were investigated. In order to investigate the relationship between structure and properties of EPS it was necessary to be able to make samples with a wide range of controlled structures. For this reason, a systematic investigation of the relationship between processing conditions and structure was performed based on a statistical experimental design. Regression analysis was conducted on the data and expressions were developed to quantify the relationships between structural parameters and processing conditions. The samples were saturated with carbon dioxide at relatively high pressure and ambient temperature and the saturated specimens were expanded at elevated temperatures. The importance of the individual processing parameters was determined. Statistical analysis of data showed that foaming time was the most important factor determining foam density, whereas saturation pressure was the most important factor determining cell size and cell density. By controlling the foaming conditions, EPS samples having the same densities and different cell sizes were produced. (C) 2003 Wiley Periodicals, Inc.