Permeation through homopolymer latex films

Abstract

The helium permeabilities of homopolymer films cast from polymer solutions and latex dispersions have been measured as a function of time. The permeability coefficients of most polymer latex films started off at a value which was considerably higher than that of the corresponding solvent‐cast film, but then dropped at a rate dependent on the polymer concerned. The permeability coefficients levelled off at a value which was closer to, but still higher than that of the equivalent solvent‐cast film. Solvent‐cast film permeabilities remained constant for the period of several months over which time they were examined. The reduction in the permeability of latex films is attributed to ageing processes occurring within the film after casting. The fact that latex film permeability coefficients are always higher than those of solvent‐cast films suggests that latex films never become completely homogeneous. The effect on permeability of the latex type and characteristics, and preparation and storage conditions has been examined. The polymer molecular weight, particle size, and surface‐change density did not appear to exert any influence, within experimental error. However, the time‐dependent permeability behavior was affected by the film preparation and storage temperatures.