Papers by Author: Jian Wang

Abstract: This article gives an overview of study on injection molding process of thermoplastic polymer SPCs. The thermoplastic polymer Polypropylene (PP) was selected as the experimental materials. Our study proves that advantages of the PP SPCs are friendly recyclability and excellent fire/matrix adhesion. PP SPCs samples had good interfacial compatibility and bonding properties. The one-component SPCs have better interfacial bonding than the multi-component SPCs. Injection molding is the most effective method with a large process window and short cycle time for processing a thermoplastic SPC. Injection molding could be developed to realize PP SPCs production.

Abstract: The optimization parison thickness can reduce the oil drum weight and meet the requirement of the minimum thickness. The profile thickness of the extruded parison can be optimized by simulation. Under different blowing pressures, extrusion blow molding non-isothermal process of the high density polyethylene oil drum with a handle was simulated by using Polyflow. The initial parison was respectively divided into 11, 51, 101 and infinite segments. After seven optimizations, the oil drum wall thickness was equal or larger than 2 mm. An appropriate inflation pressure of 0.6 MPa was obtained. The results show that the production efficiency increases with the inflation pressure increasing. With the parison segments increasing, the oil drum thickness distribution inflated from the optimized parison is more uniform and approaches to the required thickness. The oil drum mass is decreased with the segments increasing. It is necessary that the non-uniform thickness parison was produced by injection molding.

Abstract: The aim of this paper is to verify the reliability of numerical results obtained by using MPI (Moldflow Plastic Insight) for predicting the shrinkage of multi-microparts produced in one mold in microinjection molding. 3D numerical simulation (control volume finite element method) was employed. Pure and 10-20 % GRF (glass fiber reinforced) POM materials were used for the plastic material. The injection molding process was used for different parameters (mold temperature, melt temperature and injection pressure). A DOE (Design of Experiments) technique was then used to plan the numerical simulation activity of the injection molding phase. Among injection processing parameters (mold temperature, melt temperature and injection pressure), the results showed that the mold temperature is the most important factor to affect the shrinkage of multi-microparts significantly for processing parameters. The results also indicated that the processing is very well for micro-injection molding by numerical simulation. In addition, properties of polymer composites with added fillers were systematically studied. Numerical simulation results showed that the numerical resulting composites with 10–20 wt% glass particles exhibited significant improvement in shrinkage, and showed good agreement with experimental results.

Abstract: While the switchover from filling to packing is particularly crucial during injection molding, the transfers from holding to screw recovery also significantly affects the quality of molded parts. In this study, the end-point control of the holding phase based on cavity pressure was presented. It was compared with the traditional control method by holding time. The purpose of this study was to validate the feasibility of the end-point control of holding phase by cavity pressure, and to examine its consistency. The weight of the molded parts served as the main measure to probe the process’s capabilities. The results of the verification experiments revealed that the end-point control mode based on cavity pressure could yield better consistency of part weight than the traditional control method by holding time, however, the benefits were not significant. The trigger value of cavity pressure and sensor position should be considered for achieving such high process capabilities.

Abstract: While the transfer from filling to packing is particularly crucial during injection molding, the transfers from packing to holding and holding to screw recovery also significantly affect part quality. In this study, the control of the transfer from holding to screw recovery, that is the control of the end-point of the holding phase, was examined. The holding end-point control by time, cavity pressure and cavity temperature were presented. The purpose of this study was to validate the feasibility of the control methods of holding end-point by cavity pressure and cavity temperature. The qualities of injection-molded parts, weight, will serve as measures to probe their process capabilities. Recently found to be a good indicator of product quality, both cavity pressure and temperature profiles are applied here to obtain more precise control. Change of mold temperature was specially considered. After the experimental verification is conducted, the results reveal that the innovative holding end-point control by cavity temperature yields a more uniform product weight with mold temperature. It proved that the holding end-point control by cavity temperature can be used to obtain the optimum holding time and accommodate the product weight to the change of mold temperature, which is the other holding control methods cannot obtain.

Abstract: Pressure-Volume-Temperature (P-V-T) properties of two amorphous polymers (ABS and PS) were measured by an on-line testing measurement in the temperature ranges from 20 to 150 °C and pressures from 20 to 120 MPa. The on-line testing measurement is based on an injection molding machine (IMM), and it can be used to get P-V-T data of polymers directly with a special testing mold under normal processing conditions. The experimental P-V-T results of amorphous polymers under industrial processing conditions were presented. A new modified two-domain Spencer-Gilmore equation of state (EOS) was developed. The P-V-T properties were correlated by the modified Spencer-Gilmore EOS and a modified two-domain Tait EOS, showing a good agreement with measurements. The effects of sample forms were investigated. A sample with large length diameter ratio is the best one to be measured.