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Hypothesis: Thermoplastic polyurethane elastomers are generally synthesized by one of the methods of one-shot, pre-polymer and semi pre-polymer. In the preparation of polyurethanes by these methods the viscosity is increased as the reaction progresses, while the reaction is difficult to control. Therefore, the reaction extrusion method has received much attention in recent years due to high temperature reaction, better mixing of components and more convenient reaction control as well as increased reaction rate due to the elimination of post curing time. The purpose of this study was to study the process parameters of polyurethane elastomer synthesis using reactive extrusion.Methods: Here a prepolymer was synthesized with a polyester polyol (based on adipic acid) and diphenyl methane diisocyanate in a glass reactor. Then butanediol chain extender was added to the prepared prepolymer in a micro extruder at three different temperatures and residence times to obtain the final polymer. FTIR and intrinsic viscosity tests were then taken from 9 prepared samples to determine the optimum temperature and residence time.Finding: The results showed that the temperature of 165°C and the residence time of 10 min were the optimum conditions for the elastomer synthesis through reactive extrusion. Then, by designing three formulations, three thermoplastic elastomer specimens were prepared by adding butanediol chain extender to the prepolymers, in a micro-extruder, and their physical mechanical properties were studied. The results showed that using this method and the obtained process conditions, it is possible to provide polyurethane thermoplastic elastomers with desirable properties in shorter time.