In this study, various static melt mixers inside the nozzle chamber, together forming a mixing nozzle, were developed. Their performance in injection molding process was investigated using three thermoset elastomer materials with significantly different viscosity, namely nitrile butadiene rubber (NBR), ethylene propylene-diene monomer (EPDM) and fluorocarbon (FKM). The aim of this study was to minimize one of the drawbacks in injection molding resulted from the relatively short plasticizing screw. Using a short plasticizing screw, polymers having high concentrations of additives, such as thermoset elastomers, might not mix homogeneously within the short time period during the plasticizing stage. The use of these melt mixers resulted in better homogeneity and properties of the molded parts despite a curing time reduction of 10 s. This was due to the increase in mixing and shearing introduced a higher rate of crosslinking formation in the molded parts. POLYM. ENG. SCI., 58:521-527, 2018. (c) 2017 Society of Plastics Engineers