Abstract: A new measurement method for polymer melt density under different pressure and temperature was established. Based on the PVT theory of polymer melt, a melt flow rates tester was modified with a dial indicator for the measurement of the micro distance. With the modified instrument, polymer melt density can be measured under any pressure and melting temperature. By further analyzing the result, the data of the melt density was agreed with the free volume theory, i.e., the polymer melt density decreased with increasing temperature and increased with increasing pressure.

Key words: polymer, melt density, melt flow rate, piston travel distance gradient, melt temperature, measurement method, pressure