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 acids/alcohols) on free film mechanical properties was determined using an Instron tensile testing apparatus. The plasticizers were each added to the EC pseudolatex formula at levels of 25, 30 or 35% (w/w), respectively. Increasing the amount of plasticizer led to an increase in free film elongation and a decrease in modulus and stress. Differences among the individual plasticizers and classes of plasticizers evaluated were correlated with their molecular structure and a rank order could be identified. Selected films containing 30% plasticizer were evaluated under conditions of elevated temperature and humidity for storage times of up to 1 month. The results indicated that plasticizer type and amount and elevated storage temperature and humidity influence free film mechanical behavior, particularly free film elongation and toughness. These changes probably arise from further gradual coalescence of EC pseudolatex particles.