EFFECTS OF CARBOXYLATION AND NEUTRALIZING AGENT ON POLYMER INTERDIFFUSION AND WATER VAPOR PERMEABILITY OF LATEXES

摘要

The aim with this study was to further investigate polymer interdiffusion in carboxylated latex films and relate these effects to barrier properties of coated paper. Focus has been on the influence of neutralizing agent. A series of high and low-T_g model styrene/butyl acrylate latexes was prepared with one set of each carboxylated through copolymerization with methacrylic acid. The effects of impurities on film formation were investigated by comparing dialyzed dispersions with non-purified ones. Sodium hydroxide and ammonia were used as neutralizing agents. Interdiffusion in films was studied by Atomic Force Microscopy (AFM) in tapping mode and Electron Spectroscopy for Chemical Analysis (ESCA). Water vapor permeability was investigated under standard conditions. AFM images showed that a barrier against polymer chain interdiffusion was formed in films made from carboxylated latexes and that this effect was still more pronounced in films neutralized with sodium hydroxide. Water vapor permeability tests revealed however lower permeability in carboxylated films, probably due to the formation of a rigid network with low free volume available for water diffusion. Finally, purification of latex suspensions resulted in smoother films with fewer defects and reduced water vapor permeability.