Abstract: The melt elastic character of four kinds of polymers (PMMA, PS, PP, and PE-HD) was investigated using a double capillary rheometer. The effects of temperature on entrance pressure drop and stress relaxation time of melt were discussed. The entrance pressure drop and stress relaxation time of all polymer melts increased with decreasing channel size, and the smaller the channel size, the more obvious the effect. The entrance pressure drop increased with increasing shear rate, however, the effect became less obvious under high shear rates. The entrance pressure drop and stress relaxation time decreased with increasing temperature.

Key words: polymer, micro-injection molding, entrance pressure drop, stress relaxation time, elastic character