Effects of solvent on degradation of poly(vinyl chloride)

Poly(vinyl chloride) (PVC) was decomposed in t-decalin and tetralin at 300-460 °C 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 °C, 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 °C. A reaction mechanism was discussed using two parameters, atomic ratio of hydrogen and carbon (H/C) and carbon content (C_i).