The use of a drag flow device such as a twin screw extruder for polymerization and/or copolymerization processes has been studied extensively over the years. Due to the high viscosities (100 to 100000 poise) that are produced, poor backmixing is experienced in these drag flow devices. As a result, these studies have shown the extruder reactor to exhibit a "plug flow" behavior. A drag flow device has been developed that achieves good backmixing with high viscosity materials. This device incorporates two counter-rotating, nonintermeshing, screws; one screw conveying material forward, while the other conveying material backward. Theory suggests that in a plug flow reactor the copolymer composition varies (drifts) as a function of time (position) in the reactor in most cases. Conversely in a micromixed continuous stirred tank reactor (CSTR) the copolymer produced does not drift as a function with position in the reactor. It has also been shown that this drift in copolymer composition becomes more pronounced at higher conversion. Experiments were performed in a counter-rotating nonintermeshing twin screw extruder using the "backmixed" configuration and a "conventional" configuration. Two copolymer systems were investigated; butyl acrylate/styrene and butyl acrylate/butyl methacrylate. The copolymerizations were conducted at three residence times for each system and configuration to provide materials of a wide variety of conversions (13 to 97%). Monomer samples were taken at two ports in the extruder and at the die. Samples were analyzed for composition by two methods; FTIR and refractive index (RI). It was shown that the copolymer composition of samples produced in the backmixed extruder reactor does not change significantly as a function of position in the reactor. This is an indication that the copolymer composition does not drift in the reactor. Theoretically this is the behavior that exists with a chain addition copolymerization that occurs in a CSTR. Two methods (RI,FTIR) were used in the copolymer formulation (BA/Sty) and one method (FTIR) was used in the other copolymer formulation (BA/BMA). It was further shown that the difference in copolymer compositions in the two extruder reactors is more pronounced at higher conversions than at lower conversions.