Adhesion of latex films

The adhesion properties of latex films containing various kinds of surfactants were studied on glass by the use of a 180° peel test. The latex polymer was poly(2-ethyl hexyl methacrylate) (P2EHMA). The surfactants were sodium dodecyl sulfate (SDS), hexadecyl trimethylammonium bromide (HTAB), hexadecyl pyridinium chloride (HPCI), and ethoxylated nonyl phenol containing 10 ethoxy groups (NP10). Peel energy versus surfactant concentration curves were established. At medium and high peel rates (15-700 mm/min), these curves exhibit a specific shape for each surfactant: a minimum for NP10, a maximum for SDS and HPCl, and a plateau followed by a sharp increase for HTAB. In the case of HPCI-containing films, it was shown that the maximum tended to disappear when the peel rate was decreased and at 'zero peel rate' there was no longer a surfactant concentration effect on the peel energy. Analysis of the failure surfaces after peeling by FTIR-ATR, XPS, and contact angle measurements led to the conclusion that the locus of failure was also independent of the surfactant concentration. Failure took place at the top of a surfactant layer located between the substrate and the latex film. The conclusion is that surfactants strongly influence the adhesion properties of latex films, but in a complex way.