Tensile Properties of Free Films Cast from Aqueous Ethylcellulose Dispersions

Free films of two commercially available formulations of aqueous ethylcellulose dispersion differing only in plasticizer content (Surelease/E-7-7050 without silica and E-7-7060 containing dibutyl sebacate and glyceryl tricaprylate/caprate as plasticizers, respectively) were cast and coalesced at temperatures ranging between 30 and 70°C. Mechanical properties of these films were measured using tensile stress analysis. Three mechanical parameters, namely, tensile strength, work of failure, and elastic modulus, were computed from the load-time profiles of these films. The results showed that the tensile strength and elastic modulus values of the films cast from both formulations increased with the corresponding increase in coalescence temperature up to 60°C, beyond which no significant differences were observed. In the case of work of failure, however, the difference between the two formulations was observed above 60°C. The films cast from Surelease/E-7-7050 formulation without silica (dibutyl sebacate as the plasticizer) were relatively softer than those from Surelease/E-7-7060 formulation (glyceryl tricaprylate/caprate as the plasticizer). At coalescence temperatures above 50°C, the films cast from both formulations exhibited temperature-dependent plastic deformation.