A simulator to emulate the working of a counter-rotating twin screw extruder was constructed for studying devolatilization (DV) of reactive polymer solutions. The rate of the release of the volatiles was measured by an in-line mass flow meter. The operating pressure and solution temperature were measured by a pressure transducer and a thermocouple. The vapor sample compositions were determined by UV spectrophotometer. The transesterification of ethylene-vinyl acetate copolymer with 3-phenyl 1-propanol in 1-nonane solution was chosen as a model reaction. The volumetric mass transfer coefficient K(l)A was determined at various temperatures, pressures, shaft speeds and sample sizes. The effect of the reaction on K(l)A was also examined. It was found that K(l)A of the solvent (1-nonane) increases significantly with a decrease in operating pressure, and that it also increases appreciably with shaft speed, whereas temperature and the initial sample size have little effect on it. The reaction shows undetectable effect on K(l)A of the inert solvent.