The chemical modification might become an alternative to the thermal degradation of waste polyvinylchloride (PVC). Therefore, the nucleophile substitution of chlorine from flexible PVC by hydroxide (OH-), thiocyanate (SCN-), azide (N-3(-)), and iodide (I-) was investigated in ethylene glycol (EG) at 190 degrees C. With the exception of I-, all nucleophiles used resulted in substitution yields of about 20%. However, also high elimination yields were observed. When SCN was used as the nucleophile, the substitution/elimination ratio increased with decreasing temperature. The product at 150 degrees C contained a mixed structure of thiocyanate and isothiocyanate groups, while at 190 degrees C, only the structure of isothiocyanate was present the product, due to the isomerization of the -S-C=N group under the formation of -N=C=S at elevated temperatures. The substitution and dehydrochlorination yields increased with an increasing molar SCN/CI ratio. When EG was replaced by diethylene glycol (DEG) or triethylene glycol (TEG), the dehydrochlorination was found to proceed more rapidly. The use of a solvent with a lower polarity improved the contact between the solvent and the polymer; however, solvents with a lower polarity favor the elimination over the substitution. Therefore, the substitution-elimination ratio increased in the order EG > DEG > TEG. POLYM. ENG. SCI., 51: 1108-1115, 2011. (C) 2011 Society of Plastics Engineers