STUDIES OF THE MECHANICAL-PROPERTIES OF FREE FILMS PREPARED USING AN ETHYLCELLULOSE PSEUDOLATEX COATING SYSTEM

Free films produced using a commercially available ethylcellulose (EC) pseudolatex coating system (Aquacoat(R)) were prepared by a spraying method. The effect of either of 10 different plasticizers representing three chemical classes (citrate esters, di-acid esters and fatty acid s/alcohols) on free film mechanical properties was determined using an Instron tensile testing apparatus. The plasticizers were each added t o the EC pseudolatex formula at levels of 25, 30 or 35% (w/w), respect ively. Increasing the amount of plasticizer led to an increase in free film elongation and a decrease in modulus and stress. Differences amo ng the individual plasticizers and classes of plasticizers evaluated w ere correlated with their molecular structure and a rank order could b e identified. Selected films containing 30% plasticizer were evaluated under conditions of elevated temperature and humidity for storage tim es of up to 1 month. The results indicated that plasticizer type and a mount and elevated storage temperature and humidity influence free fil m mechanical behavior, particularly free film elongation and toughness . These changes probably arise from further gradual coalescence of EC pseudolatex particles.