Stereoselective modification of poly(vinyl chloride) in a twin screw extruder

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Abstract
Continuous chemical modification of poly(vinyl chloride) (PVC) with sodium benzene thiolate (NaBT) in a counter‐rotating twin screw extruder has been studied. The course of the reaction is analyzed, taking into account the physical changes of the polymer along the length of the screw. From the results, it is concluded that the modification reaction is associated with the fusion–gelation process. The reaction kinetics are determined as a function of the mean residence time with the aid of a UV tracer. Temperature profile, flow rate, and premixing are some of the processing parameters influencing the reaction, kinetics. The continuous modified polymer is analyzed in terms of thermal behavior, molecular weight, and stereochemical structure, and the results are compared with those obtained by a discontinuous melt process (Haake–Rheocord). It is confirmed that the same stereoselective substitution mechanism occurs as that in discontinuous melt with no side reactions.