Rean-Der Chien

Bio: Rean-Der Chien is an academic researcher from Taoyuan Innovation Institute of Technology. The author has contributed to research in topics: Molding (process) & Plate theory. The author has an hindex of 20, co-authored 34 publications receiving 867 citations. Previous affiliations of Rean-Der Chien include Chung Yuan Christian University.

Variable mold temperature to improve surface quality of microcellular injection molded parts using induction heating technology

Abstract: Microcellular foam injection molding provides many advantages over conventional foams and their unfoamed counterparts, but its applications are limited by visible surface quality problems such as silver streaks and swirl marks. In this study, we propose a variable mold temperature method to improve the surface quality of molded parts. Electromagnetic induction heating is used in combination with water cooling to achieve rapid mold surface temperature control during the microcellular foam injection molding process. The effect of processing parameters, such as mold temperature, melt temperature, and injection velocity on the part surface quality, was investigated using surface roughness measurements and visual inspection of the molded parts. The results show that using induction heating to increase the mold surface temperature from 100°C to 160°C can decrease surface roughness of polycarbonate moldings from 25 µm to 6.5 µm. It was also found that the flow marks formed by gas bubbles on the part surface can be removed completely at a mold temperature of 160°C. Further increases in the mold temperature show slight improvements in the surface roughness up to 180°C, at which point the surface roughness starts to level off at 5 µm. This surface roughness value reflects an 80% improvement without a significant increase in cycle time over parts molded at a mold temperature of 60°C using water heating. Higher melt temperature and faster injection speed will also improve the surface quality of microcellular injection molded parts but not as significantly. The usefulness of a variable mold temperature in improving part surface quality during microcellular foam injection molding has been successfully demonstrated. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:224–232, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20133

Polymer/carbon based composites as electromagnetic interference (EMI) shielding materials

Abstract: The extensive development of electronic systems and telecommunications has lead to major concerns regarding electromagnetic pollution. Motivated by environmental questions and by a wide variety of applications, the quest for materials with high efficiency to mitigate electromagnetic interferences (EMI) pollution has become a mainstream field of research. This paper reviews the state-of-the-art research in the design and characterization of polymer/carbon based composites as EMI shielding materials. After a brief introduction, in Section 1, the electromagnetic theory will be briefly discussed in Section 2 setting the foundations of the strategies to be employed to design efficient EMI shielding materials. These materials will be classified in the next section by the type of carbon fillers, involving carbon black, carbon fiber, carbon nanotubes and graphene. The importance of the dispersion method into the polymer matrix (melt-blending, solution processing, etc.) on the final material properties will be discussed. The combination of carbon fillers with other constituents such as metallic nanoparticles or conductive polymers will be the topic of Section 4. The final section will address advanced complex architectures that are currently studied to improve the performances of EMI materials and, in some cases, to impart additional properties such as thermal management and mechanical resistance. In all these studies, we will discuss the efficiency of the composites/devices to absorb and/or reflect the EMI radiation.

Microinjection molding of thermoplastic polymers: a review

Abstract: Microinjection molding (µIM) appears to be one of the most efficient processes for the large-scale production of thermoplastic polymer microparts. The microinjection molding process is not just a scaling down of the conventional injection process; it requires a rethinking of each part of the process. This review proposes a comparative description of each step of the microinjection molding process (µIM) with conventional injection molding (IM). Micromolding machines have been developed since the 1990s and a comparison between the existing ones is made. The techniques used for the realization of mold inserts are presented, such as lithography process (LIGA), laser micromachining and micro electrical discharge machining (µEDM). Regarding the molding step, the variotherm equipment used for the temperature variation is presented and the problems to solve for each molding phase are listed. Throughout this review, the differences existing between µIM and conventional molding are highlighted.

Micro-injection moulding of polymer microfluidic devices

Abstract: Microfluidic devices have several applications in different fields, such as chemistry, medicine and biotechnology. Many research activities are currently investigating the manufacturing of integrated microfluidic devices on a mass-production scale with relatively low costs. This is especially important for applications where disposable devices are used for medical analysis. Micromoulding of thermoplastic polymers is a developing process with great potential for producing low-cost microfluidic devices. Among different micromoulding techniques, micro-injection moulding is one of the most promising processes suitable for manufacturing polymeric disposable microfluidic devices. This review paper aims at presenting the main significant developments that have been achieved in different aspects of micro-injection moulding of microfluidic devices. Aspects covered include device design, machine capabilities, mould manufacturing, material selection and process parameters. Problems, challenges and potential areas for research are highlighted.