Terpolymers. II. Mechanical properties and transition temperatures of terpolymers of vinyl stearate, vinyl acetate, and vinyl chloride

Abstract

synopsisVinyl stearate was studied as a major internal plasticizer in terpolymers containing vinyl acetate and vinyl chloride. The terpolymers were prepared by systematically replacing vinyl acetate by close increments of vinyl stearate starting with combinations of vinyl acetate and vinyl chloride, in increments, over all compositions. For comparison of properties, a complete range of copolymers of vinyl stearate and vinyl chloride, as well as mixtures of poly(viny1 chloride) and di-2-ethylhexyl phthalate (DOP) were also made. The external plasticizer was more efficient in reducing the glass temperature than was vinyl stearate. The decline in T, with weight fraction of plasticizer was linear for the copolymers and terpolymers but concave downward with the liquid diluent. The linear decline was shown to involve mere additivity of the free volume contributed by each sidechain methylene (or methyl) group in both vinyl esters to reducing TpThe mechanism of the diluent system was more complex. However, the magnitude of the reduction of tensile modulus at a given weight fraction of DOP could be equaled or exceeded by the same amount of vinyl stearate, by increasing the vinyl acetate content of the base copolymer to 40 mole% or more. Unfortunately, the ultimate strengths and elongations of internally plasticized systems were reduced more than those of the mixtures at comparable compositions. Vinyl stearate was found to markedly retard photolytic degradation compared to both vinyl acetate and the external plasticizer in unstabdized samples having nearly the same thermal treatment. The effect was greater than could be ascribed to dilution by the long alkyl group. The production of a stearoyl radical more stable than the radicals initiating dehydrochlorination is suggested as a possible mechanism.

A rapid technique for measuring copolymer composition as a function of molecular weight using gel permeation chromatography and infrared detection

“…This copolymer has been described. 16 Its overall composition was mg/cc solution of the copolymer was prepared in tetrachloroethylene. A 4.00-cc volume of this solution was chromatographed giving a total solute load of 60.00 mg using the apparatus previously described at a Bow rate of 0.8 cc/min at room temperature.…”