열가소성 엘라스토머의 사출성형 및 자동차 웨더스트립 성형용 스택 금형 개발

Abstract

With the processing benefits of traditional thermoplastic materials such as extrusion and injection, thermoplastic elastomers (TPEs) can be applied to the eco-friendly and recyclable materials instead of thermoset rubbers. In spite of great influences on the mechanical properties and shrinkage of the molded, there has been very little research on the characterization of injection molding conditions. In addition, few application of TPEs to the former and product development by computer-aided engineering(CAE) has been achieved. In this study, the effects of molding conditions such as injection pressure, holding pressure, holding pressure time, melt temperature and mold temperature on the mechanical and shrinkage characteristics of thermoplastic vulcanizates(TPV) and thermoplastic styrene(TPS) were investigated. Development of stack mold for the automotive weather strip by CAE was also aimed. At the same time, the effects of blending ratios for the TPV/TPS blends on the mechanical properties and shrinkage characteristics were carefully studied as well. To verify the variations in mechanical properties and shrinkage, morphology was analyzed by scanning electron microscope(SEM). From this study, the following conclusions are drawn: There was no significant variation on the tensile strength and hardness of the TPEs with the increase in the holding pressure, holding pressure time and mold temperature. The increase, however, in the melt temperature lowered the tensile strength of the TPVs but increased the tensile strength of the TPSs. It was observed that injection pressure and holding pressure are the main factors for the shrinkage characteristics of the TPVs and TPSs. As the melt temperature was raised, the amount of EPDM particle in the TPV was increased and the particle size was decreased but the SEBS particles in the TPS were conglomerated, supporting the tensile strength results above. For the TPV used, stack mold different from the conventional mold for automotive weather strip and its validation and verification were made. The mechanical properties of the TPV used were estimated, followed by forming analysis with CAE and the data were used for mold design. The injection molding experiment for the newly developed stack mold for automotive weather strip was performed and the flow pattern obtained was observed to be very similar to that simulated. As a result, it is found that when it comes to mass production the stack mold developed is preferable to the conventional one.