THE EFFECT OF POLY(VINYL CHLORIDE) BLENDS ON THE MECHANICAL-PROPERTIES OF HIGHLY PLASTICIZED MEMBRANES

Solvent polymeric ion-selective electrode membranes are composed primarily of 33% polymer and 66% plasticizer. Puncture tests were conducted on membranes that incorporated blends of poly(vinyl chloride)s (PVCs), fractionated and whole, with different molecular-weight distributions. The extent to which the minor membrane component determines eight modified mechanical properties, i.e. four elastic parameters (elastic limit, tangent stiffness, resilience, flexibility) and four failure parameters (strength, secant stiffness, toughness, ductility), was investigated. The mechanical properties of fractionated and whole blends were not substantially different. Membrane ductility was always independent of thickness. Elastic parameters showed no effect of polymer number-average molecular weight, (M) over bar(n). Two of the failure parameters, however, showed a linear blending relationship based on the blend (M) over bar(n). From that relationship, the per mer contributions of PVC to the membrane strength/thickness and toughness/thickness equalled 0.96 mg mu m(-1) and 0.78 mg mm mu m(-1), respectively.