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Ryu Y, Sohn JS, Yun CS, Cha SW. Shrinkage and Warpage Minimization of Glass-Fiber-Reinforced Polyamide 6 Parts by Microcellular Foam Injection Molding. Polymers (Basel) 2020; 12:polym12040889. [PMID: 32290507 PMCID: PMC7240735 DOI: 10.3390/polym12040889] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 04/09/2020] [Indexed: 12/02/2022] Open
Abstract
Shrinkage and warpage of injection-molded parts can be minimized by applying microcellular foaming technology to the injection molding process. However, unlike the conventional injection molding process, the optimal conditions of the microcellular foam injection molding process are elusive because of core differences such as gas injection. Therefore, this study aims to derive process conditions to minimize the shrinkage and warpage of microcellular foam injection-molded parts made of glass fiber reinforced polyamide 6 (PA6/GF). Process factors and levels were first determined, with experiments planned accordingly. We simulated designed experiments using injection molding analysis software, and the results were analyzed using the Taguchi method, analysis of variance (ANOVA), and response surface methodology (RSM), with the ANOVA analysis being ultimately demonstrating the influence of the factors. We derived and verified the optimal combination of process factors and levels for minimizing both shrinkage and warpage using the Taguchi method and RSM. In addition, the mechanical properties and cell morphology of PA6/GF, which change with microcellular foam injection molding, were confirmed.
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Yun CS, Sohn JS, Cha SW. Shape-Memory-Recovery Characteristics of Microcellular Foamed Thermoplastic Polyurethane. Polymers (Basel) 2020; 12:polym12020351. [PMID: 32041158 PMCID: PMC7077500 DOI: 10.3390/polym12020351] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/21/2020] [Accepted: 01/22/2020] [Indexed: 11/16/2022] Open
Abstract
We investigated the shape-recovery characteristics of thermoplastic polyurethane (TPU) with a microcellular foaming process (MCP). Additionally, we investigated the correlation between changes in the microstructure and the shape-recovery characteristics of the polymers. TPU was selected as the base material, and the shape-recovery characteristics were confirmed using a universal testing machine, by manufacturing dog-bone-type injection-molded specimens. TPUs are reticular polymers with both soft and hard segments. In this study, we investigated the shape-memory mechanism of foamed polymers by maximizing the shape-memory properties of these polymers through a physical foaming process. Toward this end, TPU specimens were prepared by varying the gas pressure, foaming temperature, and type of foaming gas in the batch MCP. The effects of internal structural changes were investigated. These experimental variables affected the microstructure and shape-recovery characteristics of the foamed polymer. The generated cell density changed, which affected the shape-recovery characteristics. In general, a higher cell density corresponded to a higher shape-recovery ratio.
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Kim K, Ryu Y, Sohn JS, Cha SW. Effect of chemical blowing agent, melt temperature, and mold temperature on the fluidity of glass fiber-reinforced polycarbonate in injection molding. POLYM-PLAST TECH MAT 2019. [DOI: 10.1080/25740881.2019.1602142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Kihyoung Kim
- The Department of Mechanical Engineering, Yonsei University, Seoul, South Korea
| | - Youngjae Ryu
- The Department of Mechanical Engineering, Yonsei University, Seoul, South Korea
| | - Joo Seong Sohn
- The Department of Mechanical Engineering, Yonsei University, Seoul, South Korea
| | - Sung Woon Cha
- The Department of Mechanical Engineering, Yonsei University, Seoul, South Korea
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Jeong KJ, Park SY, Cho KH, Sohn JS, Lee J, Kim YK, Kang J, Park CG, Han JW, Lee HY. Correction: The Rho/ROCK pathway for lysophosphatidic acid-induced proteolytic enzyme expression and ovarian cancer cell invasion. Oncogene 2019; 38:5108-5110. [PMID: 30926886 DOI: 10.1038/s41388-019-0769-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The original version of this article contained an error in the published figures Fig 2 and Fig 3f, where the information was inadvertently duplicated. This error does not alter the conclusions of the paper. The corrected figures are published in this correction notice. The authors sincerely apologize for this error.
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Affiliation(s)
- K J Jeong
- Department of Pharmacology, Myunggok Medical Research Institute, College of Medicine, Konyang University, Daejeon, Korea
| | - S Y Park
- Department of Pharmacology, Myunggok Medical Research Institute, College of Medicine, Konyang University, Daejeon, Korea
| | - K H Cho
- Department of Pharmacology, Myunggok Medical Research Institute, College of Medicine, Konyang University, Daejeon, Korea
| | - J S Sohn
- Department of Pathology, Myunggok Medical Research Institute, College of Medicine, Konyang University, Daejeon, Korea
| | - J Lee
- Department of Microbiology, Myunggok Medical Research Institute, College of Medicine, Konyang University, Daejeon, Korea
| | - Y K Kim
- Department of Pharmacology, College of Pharmacy, Sookmyung Women's University, Seoul, Korea
| | - J Kang
- Department of Pharmacology, Myunggok Medical Research Institute, College of Medicine, Konyang University, Daejeon, Korea
| | - C G Park
- Department of Pharmacology, Myunggok Medical Research Institute, College of Medicine, Konyang University, Daejeon, Korea
| | - J W Han
- Department of Biochemistry and Molecular Biology, School of Pharmacy, Sungkyunkwan University, Suwon, Korea
| | - H Y Lee
- Department of Pharmacology, Myunggok Medical Research Institute, College of Medicine, Konyang University, Daejeon, Korea.
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Ryu Y, Sohn JS, Kweon BC, Cha SW. Shrinkage Optimization in Talc- and Glass-Fiber-Reinforced Polypropylene Composites. Materials (Basel) 2019; 12:E764. [PMID: 30845669 PMCID: PMC6427219 DOI: 10.3390/ma12050764] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 02/28/2019] [Accepted: 03/04/2019] [Indexed: 11/16/2022]
Abstract
The shrinkage of reinforced polymer composites in injection molding varies, depending on the properties of the reinforcing agent. Therefore, the study of optimal reinforcement conditions, to minimize shrinkage when talc and glass fibers (GF) (which are commonly used as reinforcements) are incorporated into polypropylene (PP), is required. In this study, we investigated the effect of reinforcement factors, such as reinforcement type, reinforcement content, and reinforcement particle size, on the shrinkage, and optimized these factors to minimize the shrinkage of the PP composites. We measured the shrinkage of injection-molded samples, and, based on the measured values, the optimal conditions were obtained through analysis of variance (ANOVA), the Taguchi method, and regression analysis. It was found that reinforcement type had the largest influence on shrinkage among the three factors, followed by reinforcement content. In contrast, the reinforcement size was not significant, compared to the other two factors. If the reinforcement size was set as an uncontrollable factor, the optimum condition for minimizing directional shrinkage was the incorporation of 20 wt % GF and that for differential shrinkage was the incorporation of 20 wt % talc. In addition, a shrinkage prediction method was proposed, in which two reinforcing agents were incorporated into PP, for the optimization of various dependent variables. The results of this study are expected to provide answers about which reinforcement agent should be selected and incorporated to minimize the shrinkage of PP composites.
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Affiliation(s)
- Youngjae Ryu
- Department of Mechanical Engineering, Yonsei University, Seoul 03722, Korea.
| | - Joo Seong Sohn
- Department of Mechanical Engineering, Yonsei University, Seoul 03722, Korea.
| | - Byung Chul Kweon
- Department of Mechanical Engineering, Yonsei University, Seoul 03722, Korea.
| | - Sung Woon Cha
- Department of Mechanical Engineering, Yonsei University, Seoul 03722, Korea.
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Kim HK, Sohn JS, Ryu Y, Kim SW, Cha SW. Warpage Reduction of Glass Fiber Reinforced Plastic Using Microcellular Foaming Process Applied Injection Molding. Polymers (Basel) 2019; 11:polym11020360. [PMID: 30960344 PMCID: PMC6419209 DOI: 10.3390/polym11020360] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Revised: 02/15/2019] [Accepted: 02/17/2019] [Indexed: 11/24/2022] Open
Abstract
This study analyzes the fundamental principles and characteristics of the microcellular foaming process (MCP) to minimize warpage in glass fiber reinforced polymer (GFRP), which is typically worse than that of a solid polymer. In order to confirm the tendency for warpage and the improvement of this phenomenon according to the glass fiber content (GFC), two factors associated with the reduction of the shrinkage difference and the non-directionalized fiber orientation were set as variables. The shrinkage was measured in the flow direction and transverse direction, and it was confirmed that the shrinkage difference between these two directions is the cause of warpage of GFRP specimens. In addition, by applying the MCP to injection molding, it was confirmed that warpage was improved by reducing the shrinkage difference. To further confirm these results, the effects of cell formation on shrinkage and fiber orientation were investigated using scanning electron microscopy, micro-CT observation, and cell morphology analysis. The micro-CT observations revealed that the fiber orientation was non-directional for the MCP. Moreover, it was determined that the mechanical and thermal properties were improved, based on measurements of the impact strength, tensile strength, flexural strength, and deflection temperature for the MCP.
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Affiliation(s)
- Hyun Keun Kim
- School of Mechanical Engineering, Yonsei University, 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.
| | - Joo Seong Sohn
- School of Mechanical Engineering, Yonsei University, 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.
| | - Youngjae Ryu
- School of Mechanical Engineering, Yonsei University, 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.
| | - Shin Won Kim
- School of Mechanical Engineering, Yonsei University, 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.
| | - Sung Woon Cha
- School of Mechanical Engineering, Yonsei University, 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.
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Sohn JS, Cha SW. Effect of Chemical Modification on Mechanical Properties of Wood-Plastic Composite Injection-Molded Parts. Polymers (Basel) 2018; 10:polym10121391. [PMID: 30961316 PMCID: PMC6401952 DOI: 10.3390/polym10121391] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 12/12/2018] [Accepted: 12/13/2018] [Indexed: 11/16/2022] Open
Abstract
Wood chips from furniture-manufacturing byproducts, which do not include adhesive or paint in the waste wood, were used for the flouring process and chemical modification of wood flour (WF). After chemical modification, the WF was mixed with polypropylene through extrusion compounding and injection-molding to prepare wood-plastic composite (WPC) injection-molded specimens for the American Society for Testing and Materials. Static contact angle measurements and stereomicroscope observations were performed. In this study, it was confirmed that the impact strength was improved by up to 55.8% and the tensile strength by up to 33.8%. The flexural modulus decreased marginally. As a result of WF chemical modification, the measured contact angle of WPC increased, which means that the wettability of the WPC specimen surface decreased. In addition, it was observed through stereomicroscopy that the whitening of the surface of the WPC specimen improved.
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Affiliation(s)
- Joo Seong Sohn
- School of Mechanical Engineering, Yonsei University, 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.
| | - Sung Woon Cha
- School of Mechanical Engineering, Yonsei University, 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.
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Ko H, Park SY, Cha EJ, Sohn JS. Primary small cell carcinoma of the urinary bladder: a case report demonstrates cytological findings in SurePath liquid-based cytology. Cytopathology 2013; 25:135-6. [PMID: 23682948 DOI: 10.1111/cyt.12067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- H Ko
- Department of Pathology, Konyang University Hospital, Daejeon, South Korea
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