Some physico-mechanical properties of esters of polyvinyl alcohol

Abstract

1. For the first time the vitrification temperatures have been determined and the mechanical properties have been characterized for the full esters termed by polyvinyl alcohol with formic, propionic, butyric, and isobutyric acids, for some of the partial-hydrolysis products of these esters, and for partial acetic esters of polyvinyl alcohol. 2. It has been established that the vitrification temperatures of the investigated polyvinyl esters (except polyvinyl formate) remain constant until the content of free hydroxyls attains 30 mole-%, and then rise as the content of ester group falls. 3. The formic esters are exceptional; the vitrification temperature passes through a minimum for a hydroxyl content of about 40–60 mole-%. 4. An explanation has been suggested for the anomalous variation in the vitrification temperature of the formic esters of polyvinyl alcohol. 5. For all of the investigated polyvinyl esters, apart from the fully substituted butyric ester, determinations have been made of the tensile strength, elastic modulus, and extension at break of films of the polymer in the highly elastic and vitreous states. 6. It has been established that, as the proportion of free hydrozyls in the polymers increased, the tensile strengths and elasticity medull of films prepared from them also increase. Formic esters are exceptional, since in the highly elastic state there is a minimum strength at a hydroxyl content of 40 mole-%. 7. For films in the highly elastic state, the extension at break varies very little as the proportion of free hydroxyls in the polymer rises from zero to 70 mole-%.