The foaming of PVC (poly(vinyl chloride)) plastisols is a complex combination of simultaneous processes, involving the curing and structural changes of the plastisol, the gas generation and the foam formation. Our comprehensive study of such processes and of the influence of plasticizer on the foam quality has shown that all the processes involved have to be adequately synchronized to obtain foams of the required quality. A series of plastisols prepared by mixing a high and a low compatible phthalate ester plasticizer in several proportions (100/0, 75/25, 50/50, 25/75, 0/100 ratios) has been studied and characterized (by means of rheology, calorimetry, thermal stability, thermomechanical properties, density, and foam morphology), to study the influence of the plasticizer in such processes with changing compatibility. We found expectable rheological and calorimetric behavior regarding the plastisols without curing; however we experienced nonlinear (unexpected) behaviors in cases of foams and plastisols being cured. To confirm such behavior and our hypothesis regarding the possible plasticizer evaporation, the thermal stability of the plastisols, precured samples and foams have been studied by themorgravimetric analysis (TGA). According to our results it can be deduced that the plasticizer loss occurring in some cases during the production of the foams or the specimens being characterized, plays an important role in the foaming process and also influences the foam quality. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012