Upon drying, latexes are transformed from milky, colloidal dispersions to transparent, continuous films in which the contours of individual coalesced particles can still be discerned. Upon ageing at room temperature, however, these latex films undergo a further gradual coalescence in which the particle contours gradually disappear and any imcompatible substances (e.g., emulsifer) are exuded to the surface. With this point of view in mind, the rate of drying at 72°CF and 50% RH was measured for three copolymer latexes: 70:30 vinylidene chloride‐n‐butyl acrylate, 67:33 ethyl acrylate‐methyl methacrylate, 67:33 styrene‐butadiene. The drying process can be divided into three stages: (1) an initial constant rate stage which persists to 60–75 vol% polymer; (2) an intermediate stage in which the rate drops off rapidly to a value 10–20 times smaller; (3) a final stage in which the rate is very much smaller and decreases very slowly with time. These stages can be correlated with the mechanism of film formation: (1) in the first stage, the particles move about with their characteristic Brownian motion, and the water evaporates from the latex at the same rate as for pure water or dilute emulsifier solution; (2) the intermediate stage begins when the particles come into irreversible contact with one another and ends with their coalescence to form a continuous film: during this stage the rate of water evaporation decreases because the water‐air interfacial area is decreasing; (3) in the final stage, the water remaining in the film escapes by diffusion, either through capillary channels between the deformed spheres or through the polymer itself. Measurement of the liquid water and water vapor transmission rates of latex film samples, taken either at the end of the intermediate stage or after sufficient ageing to ensure completion of the further gradual coalescence, showed that the rate of water loss in the final stage is initially representative of diffusion through capillary channels, but slowly and asymptotically approaches a value representative of diffusion through the polymer, presumably reaching it within the time required for completion of the further gradual coalescence (about 14 days for these copolymers). The values obtained for the three copolymers are 6.2 × 10−7, 2.9 × 10−5, and 4.4 × 10−5 g‐mil/min/cm2, respectively, in reasonable agreement with values reported in the literature for similar but not identical polymers. The values for the liquid water and water vapor transmission rates were the same.

The reactions used in the past for the preparation of phenylene sulfide and related polymers are reviewed. The Macallum polymerization is a polycondensation of an aryl halide and an inorganic sulfide or polysulfide in the absence of solvents. The monomer system studied most thoroughly is represented by the following, unbalanced equation: