Effect of stabilisers and lubricant on the thermal decomposition of chlorinated poly(vinyl chloride) (CPVC)

The thermal decomposition of pure and stabilised samples of chlorinated poly(vinyl chloride) (CPVC) was investigated using two thermal analysis techniques, thermogravimetric (TG) and differential scanning calorimetry (DSC) in atmospheres of nitrogen and air. The stabilised samples were a blend of 100 parts per hundred of resin (phr) of CPVC, 5 phr of tribasic lead sulphate (stabiliser) and I phr calcium stearate (lubricant). Two forms of samples (powder and solid) were studied. Atmospheric oxygen was found to accelerate both the dehydrochlorination stage and the decomposition of the resultant polyene. In nitrogen there was one endothermic peak at similar to 280 degrees C corresponding to the dehydrochlorination stage in both pure and stabilised-lubricated CPVC. The DSC results in air, for unstabilised CPVC showed a sharp exothermic peak during the dehydrochlorination stagie at similar to 280 degrees C, however for the stabilised-lubricated material this exotherm, was not observed. In air, TG results showed two decomposition stages for pure CPVC but three decomposition stages for stabilised and lubricated samples. One rapid decomposition stage followed by a slow-nearly linear loss of mass of the residue was observed for both samples in nitrogen. DSC results in air show a broad exothermic peak at similar to 500 degrees C for pure CPVC. For the stabilised-lubricated material, under the same conditions, the residue showed two distinct rates of oxidation from TG and two sharp exothermic peaks (in the range of 450-500 degrees C and 500-550 degrees C from DSC, possibly corresponding to two distinct components in the residue. (c) 2005 Elsevier Ltd. All.rights reserved.