Size exclusion chromatographic measurement of PVC molecular weight distributions

Aggregates that may exist in poly(vinyl chloride) (PVC) solutions at ambient temperatures compromise the accuracy of SEC measurements of molecular weight distributions. Aggregate‐free solutions can be produced in 1,2,4‐trichlorobenzene (TCB) by controlling the dissolution time and temperature. SEC measurements were made in trichlorobenzene at 110°C after dissolution for 12 h at 120°C. An on‐line continuous viscometer can be used to determine when aggregate‐free solutions have been produced. The Mark‐Houwink parameters (K = 0.161 mL/g, α = 0.762) can be used for universal calibration procedures in TCB at 110°C. Complete dissolution of the PVC affects the high molecular weight end of the molecular weight distribution. Measured M̄n values are not affected, but Mz's are much higher than those estimated, for example, from room‐temperature SEC analyses in tetrahydrofuran. Molecular weight distributions are also seen to be broader, especially for higher molecular weight PVCs.