The pyrolysis characteristics of PVC were systematically investigated using a Netzschne TG thermo-balance coupled to a quadrupole mass spectrometer. The pyrolysis conditions were 0.1 MPa of Ar,a heating rate of 10 ℃/min and a final temperature of 1000 ℃. Both the thermogravimetric properties and the simultaneous evolution of gaseous products during pyrolysis were studied. The TG/DTG results showed that as the pyrolysis temperature increases the weight loss and weight loss rate of PVC increases. Near 412 ℃ the weight loss rate attained its peak value. At higher temperatures the rate of loss gradually decreases. The gases evolved during thermogravimetric analysis were analyzed by a mass spectrometer,monitoring the relative intensity of HCl,C6H6,light hydrocarbon and chlorine-containing gases. The evolution curves showed that HCl,C6H6,light hydrocarbon and chlorine-containing gases all peak at about 416 ℃. This is consistent with the fact that the weight loss curves also peak at about 412 ℃. The extensive HCl evolution is consistent with the high chlorine content of PVC. The formation of these gases can be explained by considering these reactions: dehydrochlorination,intramolecular cyclization and the addition of HCl to unsaturated hydrocarbons.
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