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Schaible T, Bonten C. A Novel In-Line Measurement and Analysis Method of Bubble Growth-Dependent Strain and Deformation Rates during Foaming. Polymers (Basel) 2024; 16:277. [PMID: 38276686 PMCID: PMC10818267 DOI: 10.3390/polym16020277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/09/2024] [Accepted: 01/17/2024] [Indexed: 01/27/2024] Open
Abstract
Bubble growth processes are highly influenced by the elongational viscosity of the blowing agent-loaded polymer melt. Therefore, the elongational viscosity is an important parameter for the development of new polymers for foaming applications, as well as for the prediction of bubble growth processes. Thus, knowledge of the initial expansion and deformation behavior in dependency on the polymer, the blowing agent concentration, and the process conditions is necessary. This study presents a novel method for the in-line observation and analysis of the initial expansion and deformation behavior within the bead foam extrusion process. For this purpose, nitrogen as the blowing agent was injected into the polymer melt (PS and PLA) during the extrusion process. The in-line observation system consists of a borescope equipped with a camera, which was integrated into the water box of an underwater pelletizer. The camera is controlled by a developed trigger by means of angular step signal analysis of a rotary encoder on the cutter shaft of the underwater pelletizer. Thus, images can be taken at any time during the foaming process depending on the cutter position to the die outlet. It is shown that the developed method provides reliable results and that the differences of the initial expansion and deformation behavior during bubble growth can be analyzed in-line in dependency on real foaming process conditions and the type of polymer used.
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Affiliation(s)
- Tobias Schaible
- Institut für Kunststofftechnik, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany;
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2
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The Cellular Structure and Toughness of Hydrogenated Styrene-Butadiene Block Copolymer Reinforced Polypropylene Foams. Polymers (Basel) 2023; 15:polym15061503. [PMID: 36987283 PMCID: PMC10056458 DOI: 10.3390/polym15061503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 03/13/2023] [Accepted: 03/13/2023] [Indexed: 03/19/2023] Open
Abstract
Polypropylene nanocomposites containing varying amounts of Styrene-ethylene-butadiene-styrene block copolymer (SEBS) were prepared through the supercritical nitrogen microcellular injection-molding process. Maleic anhydride (MAH)-grafted polypropylene (PP-g-MAH) copolymers were used as compatibilizers. The influence of SEBS content on the cell structure and toughness of the SEBS/PP composites was investigated. Upon the addition of SEBS, the differential scanning calorimeter tests revealed that the grain size of the composites decreased, and their toughness increased. The results of the rheological behavior tests showed that the melt viscosity of the composite increased, playing a role in enhancing the cell structure. With the addition of 20 wt% SEBS, the cell diameter decreased from 157 to 66.7 μm, leading to an improvement in the mechanical properties. Compared to pure PP material, the impact toughness of the composites rose by 410% with 20 wt% of SEBS. Microstructure images of the impact section displayed evident plastic deformation, effectively absorbing energy and improving the material’s toughness. Furthermore, the composites exhibited a significant increase in toughness in the tensile test, with the foamed material’s elongation at break being 960% higher than that of pure PP foamed material when the SEBS content was 20%.
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3
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From the perspective of cells as dispersed phase in foam injection molding: Cell deformation of PP/PTFE foams. POLYMER 2023. [DOI: 10.1016/j.polymer.2023.125842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
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4
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Saini A, Yadav C, Lyu M. Cavity pressure profile study during foam injection molding and its effect on cell formation of polypropylene/chemical blowing agent foam. J Appl Polym Sci 2023. [DOI: 10.1002/app.53643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Arun Saini
- Department of Mechanical System Design Engineering Seoul National University of Science and Technology Seoul Republic of Korea
| | | | - Min‐Young Lyu
- Department of Mechanical System Design Engineering Seoul National University of Science and Technology Seoul Republic of Korea
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5
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Gao X, Chen Y, Xu Z, Zhao L, Hu D. Supercritical CO 2 Foaming of Thermoplastic Polyurethane Composite: Simultaneous Simulation of Cell Nucleation and Growth Coupling in Situ Visualization. Ind Eng Chem Res 2022. [DOI: 10.1021/acs.iecr.2c02431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xiulu Gao
- State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Yichong Chen
- State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Zhimei Xu
- State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Ling Zhao
- State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Dongdong Hu
- State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
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6
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The controlled preparation of secondary cells realizes the bimodal structure through two different pressure drop methods. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.125198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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7
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Visual observation and Numerical Studies of bubble formation of polypropylene chemical foaming system in the different injection foaming environment. JOURNAL OF POLYMER RESEARCH 2022. [DOI: 10.1007/s10965-022-03183-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Chai J, Wang G, Zhang A, Dong G, Li S, Zhao J, Zhao G. Microcellular injection molded lightweight and tough poly (L-lactic acid)/in-situ polytetrafluoroethylene nanocomposite foams with enhanced surface quality and thermally-insulating performance. Int J Biol Macromol 2022; 215:57-66. [PMID: 35718146 DOI: 10.1016/j.ijbiomac.2022.06.091] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 06/11/2022] [Accepted: 06/11/2022] [Indexed: 01/13/2023]
Abstract
High-performance microcellular polymer foams have been widely used all over the world, while the excessive usage of petroleum-based polymers caused serious environmental problems. As the eco-friendly awareness is increasing significantly, poly (L-lactic acid) (PLLA), as a typical biomass polymer, has gradually attracted widespread attention. However, the slow crystallization and poor melt strength of PLLA lead to low foaming ability and thus limiting its industrial applications. Herein, a novel and scalable strategy by coupling in-situ fibrillation and mold-opening microcellular injection molding (MOMIM) was developed to fabricate lightweight and tough PLLA/polytetrafluoroethylene (PTFE) foams. Thanks to the reticulated in-situ PTFE nanofibrils with a diameter of 100-200 nm, the crystallization and viscoelasticity of PLLA were dramatically promoted, and further contributing to its foaming ability. The expansion ratio of the MOMIM PLLA/PTFE foam was increased by 86 % compared with the regular microcellular injection molded (RMIM) PLLA foam. Moreover, the lower foam density and the toughening effect of PTFE nanofibrils resulted in the outstanding ductility of the PLLA/PTFE foams, whose tensile elongation, flexural strength, and impact strength were maximally increased by 52 %, 28 %, and 48 %, compared with PLLA foams. More importantly, the thermally-insulating performance and surface quality of PLLA/PTFE foams were also greatly improved.
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Affiliation(s)
- Jialong Chai
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, Shandong 250061, China
| | - Guilong Wang
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, Shandong 250061, China; School of Mechanical & Vehicle Engineering, Linyi University, Linyi, Shandong 276005, China.
| | - Aimin Zhang
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, Shandong 250061, China
| | - Guiwei Dong
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, Shandong 250061, China; State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, China
| | - Shuai Li
- School of Mechanical & Vehicle Engineering, Linyi University, Linyi, Shandong 276005, China
| | - Jinchuan Zhao
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, Shandong 250061, China.
| | - Guoqun Zhao
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, Shandong 250061, China
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9
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Hasanzadeh R, Azdast T, Mojaver M, Darvishi MM, Park CB. Cost-effective and reproducible technologies for fabrication of tissue engineered scaffolds: The state-of-the-art and future perspectives. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.124681] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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10
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Wang C, Shaayegan V, Costa F, Han S, Park CB. The critical requirement for high-pressure foam injection molding with supercritical fluid. POLYMER 2022. [DOI: 10.1016/j.polymer.2021.124388] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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11
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Shaayegan V, Wang C, Ataei M, Costa F, Han S, Bussmann M, Park CB. Supercritical CO2 utilization for development of graded cellular structures in semicrystalline polymers. J CO2 UTIL 2021. [DOI: 10.1016/j.jcou.2021.101615] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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12
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Rostami M, Azdast T, Hasanzadeh R, Moradian M. A study on fabrication of nanocomposite polyethylene foam through extrusion foaming procedure. CELLULAR POLYMERS 2021. [DOI: 10.1177/02624893211040949] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Foaming a polymer not only turns it into a lightweight material but also gives some special properties to it. However, the most important issue is controlling the foaming process to achieve a desirable structure with high cell density and low relative density. In the present study, the extrusion foaming process of polyethylene was studied through stepwise amendments. An innovative extrusion system was designed and implemented to produce extrusion foams under different material and process conditions using N2 as blowing agent. In the first step, the final cooling condition was investigated. The air-cooling condition led to a higher cell density/lower cell size compared to the water-cooling condition although a higher relative density was obtained. In the second step, the effects of the addition of talc and the synergetic effect of talc/nanoclay at different contents were investigated in detail. The hybrid of talc/nanoclay had a noticeably improving effect on the cellular structure. In the third step, the effects of processing parameters including the die temperature and screw speed were studied on the foam properties. Finally, up to 49.4% decrease in the relative density of samples was observed, also cell densities up to 2.5 × 104 cell/cm3 and cell sizes as small as 280 µm were achieved.
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Affiliation(s)
- Milad Rostami
- Mechanical Engineering Department, Faculty of Engineering, Urmia University, Urmia, Iran
| | - Taher Azdast
- Mechanical Engineering Department, Faculty of Engineering, Urmia University, Urmia, Iran
| | - Rezgar Hasanzadeh
- Mechanical Engineering Department, Faculty of Engineering, Urmia University, Urmia, Iran
| | - Milad Moradian
- Mechanical Engineering Department, Faculty of Engineering, Urmia University, Urmia, Iran
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Ding Y, Hassan MH, Bakker O, Hinduja S, Bártolo P. A Review on Microcellular Injection Moulding. MATERIALS 2021; 14:ma14154209. [PMID: 34361403 PMCID: PMC8348032 DOI: 10.3390/ma14154209] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/23/2021] [Accepted: 07/26/2021] [Indexed: 12/02/2022]
Abstract
Microcellular injection moulding (MuCell®) is a polymer processing technology that uses a supercritical fluid inert gas, CO2 or N2, to produce light-weight products. Due to environmental pressures and the requirement of light-weight parts with good mechanical properties, this technology recently gained significant attention. However, poor surface appearance and limited mechanical properties still prevent the wide applications of this technique. This paper reviews the microcellular injection moulding process, main characteristics of the process, bubble nucleation and growth, and major recent developments in the field. Strategies to improve both the surface quality and mechanical properties are discussed in detail as well as the relationships between processing parameters, morphology, and surface and mechanical properties. Modelling approaches to simulate microcellular injection moulding and the mathematical models behind Moldex 3D and Moldflow, the two most commonly used software tools by industry and academia, are reviewed, and the main limitations are highlighted. Finally, future research perspectives to further develop this technology are also discussed.
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Affiliation(s)
- Yifei Ding
- Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Mohammed H Hassan
- Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Otto Bakker
- Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Srichand Hinduja
- Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Paulo Bártolo
- Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK
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14
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Li S, Sun X, Wang R, Hu Y, Ma X, Wang J. Experimental investigation on the forming and evolution process of cell structure in gas counter pressure assisted chemical foaming injection molded parts. J CELL PLAST 2020. [DOI: 10.1177/0021955x20950224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
By using a standard stretch spline as the research object, the influence of gas counter pressure (GCP) technology on melt foaming behavior in chemical foaming injection molding (CFIM) process was investigated. Related experimental line for GCP assisted CFIM foam was designed, and the effect of GCP technology on melt flow front, spline surface quality and internal cell was studied. According to the results obtained from the experiment, two critical GCP pressures and one critical GCP holding time were innovation proposed. Two critical GCP pressures are the critical GCP pressure of melt flow front cell not cracking and the critical GCP pressure of melt not foaming, respectively. The critical GCP holding time is the secondary foaming behavior time. Based on the proposed critical GCP pressures and critical GCP holding time, the influence mechanism of GCP technology on melt foaming action during CFIM process was revealed.
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Affiliation(s)
- Shuai Li
- School of Mechanical &Vehicle Engineering, Linyi University, Linyi, PR China
| | - Xuemei Sun
- School of Mechanical &Vehicle Engineering, Linyi University, Linyi, PR China
| | - Rui Wang
- School of Mechanical &Vehicle Engineering, Linyi University, Linyi, PR China
| | - Yanyan Hu
- Department of Pediatrics, Linyi People’s Hospital, Linyi, PR China
| | - Xiaofei Ma
- School of Mechanical &Vehicle Engineering, Linyi University, Linyi, PR China
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15
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Kastner C, Steinbichler G. Theoretical Background and Automation Approach for a Novel Measurement Method for Determining Dynamic Solubility Limits of Supercritical Fluids in Injection Foam Molding. POLYM ENG SCI 2019. [DOI: 10.1002/pen.25288] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Clemens Kastner
- Institute of Polymer Injection Molding and Process AutomationJohannes Kepler University Linz Altenberger Strasse 69, A‐4040 Linz Austria
| | - Georg Steinbichler
- Institute of Polymer Injection Molding and Process AutomationJohannes Kepler University Linz Altenberger Strasse 69, A‐4040 Linz Austria
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16
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Accurate theoretical modeling of cell growth by comparing with visualized data in high-pressure foam injection molding. Eur Polym J 2019. [DOI: 10.1016/j.eurpolymj.2019.07.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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17
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Zhao J, Wang G, Zhang L, Li B, Wang C, Zhao G, Park CB. Lightweight and strong fibrillary PTFE reinforced polypropylene composite foams fabricated by foam injection molding. Eur Polym J 2019. [DOI: 10.1016/j.eurpolymj.2019.07.016] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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18
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Tromm M, Shaayegan V, Wang C, Heim HP, Park CB. Investigation of the mold-filling phenomenon in high-pressure foam injection molding and its effects on the cellular structure in expanded foams. POLYMER 2019. [DOI: 10.1016/j.polymer.2018.11.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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19
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Xie P, Wu G, Cao Z, Han Z, Zhang Y, An Y, Yang W. Effect of Mold Opening Process on Microporous Structure and Properties of Microcellular Polylactide⁻Polylactide Nanocomposites. Polymers (Basel) 2018; 10:polym10050554. [PMID: 30966588 PMCID: PMC6415379 DOI: 10.3390/polym10050554] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 05/06/2018] [Accepted: 05/09/2018] [Indexed: 11/16/2022] Open
Abstract
Cell structure is a key factor that determines the final properties of microcellular polylactide (PLA) product. In the mold opening process, adjusting the rate of mold opening can effectively control cell structure. PLA and PLA composites with a void fraction as high as 50% were fabricated using the mold opening technique. The effects of mold opening rate and the addition of nanoclay on the cell structure, mechanical properties, and surface quality of microcellular PLA and PLA composites samples were investigated. The results showed that finer cell structure was received in the microcellular PLA samples and the surface quality was improved effectively when decreasing the rate of mold opening. The effect of mold opening rate on the foaming behavior of microcellular PLA⁻nanoclay was the same as that of microcellular PLA. The addition of 5 wt % nanoclay significantly improved the foaming properties, such as cell density, cell size, and structural uniformity, which consequently enhanced the mechanical properties of foams and the surface quality.
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Affiliation(s)
- Pengcheng Xie
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Gaojian Wu
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Zhida Cao
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Zhizhong Han
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Youchen Zhang
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Ying An
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Weimin Yang
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China.
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Yilmaz G, Ellingham T, Turng LS. Improved Processability and the Processing-Structure-Properties Relationship of Ultra-High Molecular Weight Polyethylene via Supercritical Nitrogen and Carbon Dioxide in Injection Molding. Polymers (Basel) 2017; 10:E36. [PMID: 30966070 PMCID: PMC6415066 DOI: 10.3390/polym10010036] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 12/27/2017] [Accepted: 12/28/2017] [Indexed: 01/01/2023] Open
Abstract
The processability of injection molding ultra-high molecular weight polyethylene (UHMWPE) was improved by introducing supercritical nitrogen (scN₂) or supercritical carbon dioxide (scCO₂) into the polymer melt, which decreased its viscosity and injection pressure while reducing the risk of degradation. When using the special full-shot option of microcellular injection molding (MIM), it was found that the required injection pressure decreased by up to 30% and 35% when scCO₂ and scN₂ were used, respectively. The mechanical properties in terms of tensile strength, Young's modulus, and elongation-at-break of the supercritical fluid (SCF)-loaded samples were examined. The thermal and rheological properties of regular and SCF-loaded samples were analyzed using differential scanning calorimetry (DSC) and parallel-plate rheometry, respectively. The results showed that the temperature dependence of UHMWPE was very low, suggesting that increasing the processing temperature is not a viable method for reducing injection pressure or improving processability. Moreover, the use of scN₂ and scCO₂ with UHMWPE and MIM retained the high molecular weight, and thus the mechanical properties, of the polymer, while regular injection molding led to signs of degradation.
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Affiliation(s)
- Galip Yilmaz
- Polymer Engineering Center, Department of Mechanical Engineering, University of Wisconsin⁻Madison, Madison, WI 53706, USA.
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI 53715, USA.
| | - Thomas Ellingham
- Polymer Engineering Center, Department of Mechanical Engineering, University of Wisconsin⁻Madison, Madison, WI 53706, USA.
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI 53715, USA.
| | - Lih-Sheng Turng
- Polymer Engineering Center, Department of Mechanical Engineering, University of Wisconsin⁻Madison, Madison, WI 53706, USA.
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI 53715, USA.
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