EFFECTS OF FILM STRUCTURE ON MECHANICAL AND ADHESION PROPERTIES OF LATEX FILMS

In order to investigate the effect of the particular structure of late x films on mechanical (stress-strain behaviour) and adhesion (measured by peeling) properties, this work compares these characteristics for latex films and corresponding ''solution films''. Solution films were obtained by dissolving the latex film in an appropriate solvent and fo rming a new film by evaporating the solvent. In this way, the latex an d solution films have exactly the same composition but different struc tures. Four different systems were studied, namely a homopolymer of 2- ethyl hexyl methacrylate, a copolymer of styrene and butyl acrylate, a copolymer of butyl acrylate with a zwitterionic monomer, and, finally , an ethyl acrylate-methyl methacrylate copolymer partially grafted on to a hydrophilic polyester. It was shown that latex films have Young's moduli systematically higher than the corresponding solution films. T his is due to the fast that the hydrophilic shells of the latex partic les form a continuous phase in the latex film which increases the modu lus thanks to polar interactions. Modeling was possible using an appro priate equation (Palierne's Model) which allowed the determination of the modulus and volume fraction of the shell phase, without adjustable parameter. On the other hand, adhesion energy for latex films is alwa ys smaller than for solution films. This is interpreted in terms of st ructure of the film-support interface and interface and dissipative pr ocesses within the bulk of the film. (C) 1997 Elsevier Science Ltd.