Spray-coated and solution-cast ethylcellulose pseudolatex membranes

Membranes of dibutyl sebacate (DBS) plasticized ethylcellulose pseudolatex were prepared by spray-coating and solution-casting methods for the studies of their transport and mechanical properties. The structure of sprayed membranes was more porous than that of cast membranes, so the sprayed membranes were more permeable than the cast membranes. The permeabilities of drug or water vapor through sprayed membranes decreased with increasing plasticizer concentration; on the contrary, those through cast membranes increased with increasing plasticizer concentration. The diffusion through pores accounts for the transport through sprayed membranes, while the solution-diffusion through plasticized polymer phase may become an important role for that through the cast membranes. Mechanically, the sprayed membranes were harder and more brittle than the cast membranes of similar formulation, but membranes prepared from both methods possessed similar breaking tensile strength. The tensile strength and Young's modulus were reduced and the elongation was improved with increasing plasticizer concentration for both kinds of membranes. The sprayed membranes would become less permeable and tougher after the post thermal treatment as the degree of coalescence between the latex particles in the membranes was enhanced. (C) 1999 Elsevier Science B.V. All rights reserved.