The effect of surfactant and copolymer polarity on the film‐formation temperatures of some vinylidene chloride copolymers

Abstract

AbstractThe minimum temperature required for a copolymer emulsion to form a continuous film Tmf, and the glass transition temperature Tg of the copolymer were studied for vinylidene chloride‐acrylate copolymers and vinylidene chloride‐acrylonitrile copolymers. The Tmf and Tg were studied as a function of the nature of the surfactant used in the preparation of the emulsion. The Tmf was found to deviate markedly from the Tg for most compositions and the Tmf‐composition curves were found to be similar in shape to the Tg‐composition curves, exhibiting a maximum in the case of the acrylate copolymers. The quantity Tmf—Tg changes from negative to positive with decreasing polar character of the methyl and ethyl acrylate copolymers. This is especially obvious in the ethyl acrylate copolymer. The high Tmf values for copolymers containing acrylonitrile is attributed to strong interchain forces, which orientate the neighboring segments in a latex particle unfavorably for interpenetration with other particles. The nature of the surfactant used in the preparation of the emulsion was found to affect the Tmf. Emulsions of nonpolar, hydrophobic copolymers containing a blend of anionic and nonionic surfactants have a higher Tmf than those containing only anionic surfactant; however, with an increase in the amount of hydrophilic units in the copolymer the converse is true, except in the case of the highly polar copolymers of vinylidene chloride‐methyl acrylate, in which the Tmf's for both surfactant systems are similar.