Papers by Author: D.Y. Zhao

Abstract: The rheological characteristics of four polymer melts (PS, PMMA, PP and HDPE) are investigated by a capillary rheometer with the die diameters from 1.5mm to 0.5mm.The effects of temperature on shear viscosity and the effects of both temperature and shear rate on non-Newton exponent of melts are discussed when the die diameter is 0.5mm. The results show that the shear viscosity of four polymers decreases with the rise of shear rate. The shear viscosity of PS and PMMA increases with the decrease of die diameter, the shear viscosity of PP and HDPE decreases with die diameter and minute differences of shear viscosity with different die diameters are observed with the growth of shear rate. When the die diameter is 0.5mm, Arrhenius equation is found to be suitable to describe the relations between shear viscosity and temperature for four polymer melts. The non-Newton exponents of four polymer melts increase with the temperature and decrease with the rise of shear rate.

Abstract: Plastic profiles produced by extrusion die are cooled down and calibrated by calibrators, so it is an important basis to solve design problems of calibrators that how to obtain the transient temperature field of cooling process of hot plastic profiles. Based on the analysis of heat transfer ways during the cooling process, computation model, initial and boundary conditions are studied deeply, and then ANSYS is applied to simulate the cooling process of plastic profiles. Lastly, the transient temperature field of the cooling process is gain. Results of the numerical simulation show that the temperature drops of functional blocks, main-walls and inner-ribs are reduced in order of priority. Based on the results, the cooling water channels can be adjusted in order to improve the distributing uniformity of temperature field. All this is effective to the calibrators’ design.