Rigid poly(vinyl chloride) (PVC) gelation in the brabender measuring mixer. II. Description of PVC gelation in the torque inflection point

This article discusses the transitory stage between the minimum and the maximum of the torque, which corresponds to an inflection point on the torque curve (called point G). The unplastified compound of poly (vinyl chloride) (PVC) (Polanwil S-61) was processed in various temperatures between 150 and 200 degrees C, by rotors speeds in the range from 5 to 40 min(-1). The progress of gelation was estimated basing on DSC thermograms and on the rheological measurements, which were realized by means of specially constructed MFR apparatus. The morphological changes of processed compound were characterized by scanning electron microscopy (SEM). It was found that a general description of gelation progress demand both, the microscopic observation as well DSC and MFR measurements. More significant advancement of gelation, as observed by SEM, was achieved by lower shear rates. However, it may be stated that by reaching an inflection point on the torque curve, the PVC compound may not be treated as a polymer where the gelation process was completed. (c) 2006 Wiley Periodicals, Inc.