The Influence of Metal Soap Thermal Stabilizers on the Dehydrochlorination of Flexible PVC

The influence of metal soap thermal stabilizers on the dehydrochlorination of flexible PVC was studied in this paper.The stabilizers were mixtures of calcium stearate,zinc stearate and barium stearate with series of different ratios.Each formulation was evalvated by the Congo Red test in which both the temperature and the time for the dehydrochlorination of flexible PVC were measured as the sample was heated at 180℃ in a test tube.The results of the Congo Red test showed that calcium stearate,zinc stearate,or barium stearate which was used single is not a good thermal stabilizer for flexible PVC.However,zinc stearate/calcium stearate with 1∶2(mass ratio)as stabilizers for flexible PVC is more effective than which with 1∶1,2∶1,1∶3and 3∶1.At the same time,zinc stearate/barium stearate with 1∶2as stabilizers for flexible PVC is superior to which with 1∶1and 2∶1.The most effective stabilizer for flexible PVC is the mixture of calcium stearate,zinc stearate and barium stearate together with the mass ratio of 1∶1∶1,which can obviously restrain the early colour changes of flexible PVC.