Infrared spectral changes in PVC and plasticized PVC during gelation and fusion

Abstract The behaviour of PVC and PVC plastisols has been studied during their thermal treatment using an in situ FTIR technique. The plasticizer introduces certain modifications in the spectrum of the resin which are more marked in the case of the more compatible plasticizers. The A 1427 A 1435 and A 637 A 616 ratios of the intensities of the crystalline and amorphous bands of the resins, decrease in the plastisols when increasing the compatibility of the plasticizer. On the other hand, when the plastisol undergoes the gelation process, a great decrease of these ratios is observed, showing that the increase in temperature produces a decrease in the amount of the crystalline phase in the resin with respect to the amorphous phase. This behaviour has also been observed when the resin is heated without plasticizer, and is a reversible process. The CO band corresponding to the plasticizer shows a different behaviour to the resin bands. When the temperature increases, a shift to lower wavenumbers is observed. This displacement is irreversible (the band does not recover its original location after cooling) and the process occurs in a relative narrow temperature interval. This temperature range, where the carbonyl band suffers these changes, is in good agreement with the gelation temperature as measured by other techniques.