EFFECT OF ALKYL PHTHALATE PLASTICIZERS ON PERMEATION OF WATER-VAPOR THROUGH PVC MEMBRANES

PVC membranes plasticized with various concentrations of a di-n-alkylp hthalate (methyl, ethyl, butyl or octyl) were studied for their water vapour permeation (WVP) properties. The rates of WVP through them were estimated under steady state by permeating the vapour through the mem brane under the vapour pressure differential of approximately 100% to 0% relative humidities at 25-degrees-C. The rates of WVP were found to decrease with an increase in the size of the alkyl group of the phtha late but increased with its concentration. The maintenance of the prop erty by the membranes being critical for their long-term applications, the measurements were also repeated on the membranes aged for 250 day s at intervals of 50 days. The WVP data indicate that membranes contai ning medium concentrations, i.e. 17.5-20% of the plasticizers have bet ter maintenance of the property during ageing and also in handling wit h good mechanical strength.