Papers by Author: M.C. Song

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: Compared with hot embossing, microfluidic chips injection molding is higher efficiency process and more suitable for mass production, but the quality control for injection molding is much more complex. Experiments indicate that the incomplete replication of the micro-channel and the sink mark for microfluidic chips are the chief defects to the molding. Simulation and theoretical analysis show that the stagnant flow of the melt in micro-channel and the shrinkage difference of the chips in different directions are the main reasons for molding defect. A set of new methods that how to control process parameter, design mold, and select polymer material is proposed to reduce or avoid the defects.

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.