Anomalous behaviour of PVC–CPVC–CPE blends

Chlorinated PVC (CPVC) is widely used for high temperature applications, e.g. hot water pipes. To improve processing, it is usually mixed with PVC. These systems are brittle, therefore impact modifiers are also added to CPVC formulations. The usual modifiers are MBS types. In spite of chemical similarity, chlorinated polyethylene (CPE) is not usually applied. Multiphase structures were observed while preparing alloys of these chlorine containing polymers, however, the polymers show ‘technological compatibility' having good properties. It has been discovered by dynamic mechanical tests that the glass-transition temperature of CPVC increases when mixed with CPE of low (about 0°C) T _g while the T _g of CPE decreases. This is contrary to general rules, but can be explained by the structure of the polymers tested. The phase structure formed has been investigated by scanning electron microscopy.