Poly(vinyl chloride) (PVC) was decomposed in t-decalin and tetralin at 300-460 degreesC under an initial nitrogen pressure of 4.0 MPa. To aid mechanistic discussions, some reactions were also performed in the absence of solvent. In the beginning of the reaction at 300 degreesC, PVC was converted to THF-insoluble dehydrochlorinated PVC (idcPVC) irrespective of the presence of solvent, by liberation of hydrogen chloride. In the reactions without solvent, oil and solid carbon were produced from idcPVC predominantly by degradation and condensation reactions respectively. In the presence of solvent, idcPVC was converted into oil directly or via THF-soluble dehydrochlorinated PVC (sdcPVC). Particularly in tetralin, the decomposition of idcPVC into oil was accelerated significantly over 440 degreesC. A reaction mechanism was discussed using two parameters, atomic ratio of hydrogen and carbon (H/C) and carbon content (C-i). (C) 2003 Elsevier Science Ltd. All rights reserved.