The swelling of polymer systems in solvents. I. Method for obtaining complete swelling–time curves

A photometric method for measuring the swelling of polymers in solvents from zero time to equilibrium has been described. The method consists in following continually the growing “shadow” of the specimen as it imbides the solvent. Equipment details and method of operation are discussed. Typical swelling–time curves for butyl vulcanizates are reported. These serve as examples of the rapidity and reproducibility of the method and also as demonstrations of the completeness of solvent uptake. Essential agreement between the results on volume swelling at equilibrium obtained by the photometric method and by the conventional gravimetric method is observed. The new method is important in that the rate of swelling can be measured. Its use in this regard in studying the diffusion of liquids in polymers will be referred to subsequent papers in this series.