Modification of Polysulfones by Carboxylic Acids

Abstract

The modification of aromatic polysulfones (PSU) in the melt in continuous mixing aggregates (on the small-scale: twin-screw microcompounder; on the large-scale: twin-screw extruder) by low-molecular weight dicarboxylic acids is presented. Owing to the drastic conditions experienced by the melt in the extruder operating at 320 °C, chain scission of the polysulfones as well as the formation of reactive groups attached to the PSU chains was expected, using either trimellitic acid anhydride or terephthalic acid as dicarboxylic acids. However, no functional groups indicating a reaction between the PSU and the carboxylic acids were detected in the melt-processed PSU compounds. Nevertheless, the resulting thermal and mechanical properties of the PSU compounds were influenced remarkably by the carboxylic acids due to their different mixing behavior with the PSU melt. The tensile stiffness and strength of the compounds were significantly increased in comparison with the PSU reference. PSU compounds containing the trimellitic acid anhydride (at concentrations exceeding 5.7 wt.%) showed a particularly high strength at break, while all compounds had a lower toughness in comparison with the neat PSU.