The factors affecting pressure losses during extrusion of polymer melts are discussed in the present article. The rheological properties of an unvulcanized rubber compound were examined by using a Monsanto processability tester (MPT) under experimental conditions of temperatures varied 90 to 120 degreesC and shear rates from 10(2) to 10(3) s(-1). Furthermore, a set of dies with different entry angle (2 alpha) was selected to identify the effects of die angles on pressure losses in capillary extrusion of the sample fluid. It was found that the total pressure drop (DeltaP) decreased when 2 alpha < 75 degrees, and then increased with increasing 2. The DeltaP reached the minimum value when 2 alpha is around 75 degrees. It suggests that the natural converging angle of the sample fluid be about 75 degrees under the experimental conditions, according to the research results presented in previous work.