Controlled release PVC membranes: Influence of phthalate plasticizers on their tensile properties and performance

The design of controlled release polymer dispensers (CRPD) for effective re lease of the active ingredients at desired rates requires a careful study a nd generation of data on several properties of the polymer membranes. Prese nce of optimum tensile properties is one of the prerequisites for the CRPD in deciding their suitability for application in the fields. Polyvinylchlor ide (PVC) membranes containing di n-alkyl phthalate (alkyl = methyl, ethyl, butyl & octyl) with concentrations ranging from 10-30% with an increment o f 2.5% were prepared. The tensile strength and percent elongation of these membranes as a function of concentration of the phthalate plasticizers, the ir size and aging period were performed. An increase in the tensile strengt h with increasing phthalate content was noticed up to 17.5% phthalate. Then followed a decrease with further increase of phthalate content. In contras t, the percent elongation was observed to increase constantly with increase d concentration of the plasticizer. The ambiguous increase in the tensile s trength up to 17.5% plasticized films is attributed to the antiplasticizati on effect of the plasticizer. The properties showed a linear behavior with respect to the size of the alkyl chain length and also the period of aging. The membranes with 17.5% and 20% were found to have optimum tensile proper ties and good property retention with aging for their application in contro lled release of agrochemicals.