STUDIES ON THE WETTING BEHAVIOR OF POLYMER MELTS ON SOLID-SURFACES USING THE WILHELMY BALANCE METHOD

A Wilhelmy balance method has been used to measure the wetting tension of polymer melts on solid surfaces at high temperatures. The applicat ion of thin quartz fibres or platinum wires allowed fast and reliable surface tension values for polypropylene and epoxy resin melts to be o btained without knowledge of the density of these melts. The measuring technique is also suitable for investigating the surface activity of additives or polar components in these polymer melts. The plot of gamm a cos Theta versus concentration for two commercially applied additive s (benzoin, butyl acrylate) yielded different surface activities of th ese additives in an epoxy resin melt. The plot of gamma cos Theta vers us temperature provides different temperature coefficients of the wett ing tension for each additive concentration. It was found that -d(gamm a cos Theta)/dT was increased in the presence of the additives. The ga mma cos Theta versus temperature curves permit conclusions concerning the change in flow properties of polymer coating systems due to additi ves. Depending on the type of interaction at the solid/liquid interfac e - physical or chemical interactions - different wetting kinetics hav e been found for unmodified and chemically modified polypropylene melt s on untreated and aminosilane-treated glass fibres. Thus, it is assum ed that these measurements permit a more fundamental and quantitative understanding of the mechanism of interface formation in fibre-reinfor ced polymer composites.