The investigation of relaxation mechanism and model of polystyrene in high‐elastic state

Abstract The relaxation behavior of polymer in its high elastic state is a key factor which determines the molding process and accuracy of its products. Polystyrene with different molecular weights are selected as research object and its relaxation time at different temperatures was tested by torque rheometer. Combining the relationship of “temperature‐relaxation time”, to deeply analyze its relaxation mechanism, a physical model of high elastic relaxation time of polystyrene based on the movement of molecular chains was established, and the change of the physical model at different temperatures was explained. The corresponding mathematical model was obtained by analyzing the influence of the weight average molecular weight M w , dispersion D, and temperature T parameters of polystyrene on its relaxation time. The results of experiments and model calculations reveal that the relaxation time of polystyrene under high elasticity does not continue to decrease with the increase of temperature, but it changes in an M‐shape with the increase of temperature, that is, the relaxation time shows an upward trend at 155°C – 160°C and a downward trend at 160°C – 165°C. It has an increasing trend at 165°C – 170°C, and a decreasing trend at 170°C – 175°C. Polystyrenes with different molecular weights and dispersion degrees have different M forms. The research results have theoretical guiding significance for polymer processing.