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High-Precision Thin Wall Bipolar Plates for Fuel Cell Applications via Injection Compression Molding with Dynamic Mold Temperature Control. Polymers (Basel) 2022; 14:polym14142799. [PMID: 35890575 PMCID: PMC9318047 DOI: 10.3390/polym14142799] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 07/05/2022] [Accepted: 07/07/2022] [Indexed: 11/17/2022] Open
Abstract
In recent years, the demand for polymer compound solutions for the application of bipolar plates in polymer electrolyte membrane fuel cells (PEMFC) has increased continuously due to significant cost and lifetime advantages compared to metallic solutions. The main challenge of the compounds is the high filler content required to ensure sufficient electrical conductivity of the bipolar plates. The associated increase in viscosity and simultaneously increased thermal conductivity limit the conventional injection molding process in terms of achievable flow path length to wall thickness ratios (plate aspect ratio). In order to evaluate the extent to which highly modified electrically conductive polymer material systems can be processed into thin-walled and highly dimensionally stable bipolar plates, an injection compression molding process with dynamic mold temperature control (ICM-DT) has been developed. For this purpose, a compound was prepared from polypropylene (PP) and graphite-flakes. The compound was characterized with respect to the achieved filler content, the electrical conductivity, as well as the pressure- and temperature-dependent solidification range. The ICM-DT experiments were carried out by varying the maximum mold temperature and the compression force. In addition, the process was designed with multiple compression and decompression steps to account for a possible pressure-dependent solidification of the compound. The plates were characterized with respect to the achieved plate aspect ratio and the flow-path-dependent dimensional thickness stability. It was shown that the plate aspect ratio could be increased by up to 125% with the maximum filler content compared to conventional injection molding processes provided in the literature. With the multi-stage ICM-DT process, it was also possible to optimize the thickness dimensional stability with a maximum deviation of 3% over the flow path.
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Crystallization Behavior of Rapid-Compression-Induced Mesomorphic Isotactic Polypropylene during Uniaxial Stretching at Different Temperatures. POLYMER CRYSTALLIZATION 2022. [DOI: 10.1155/2022/5750961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The uniform bulk mesomorphic iPP is prepared by rapid compression, and its structural evolution under stretching at different temperatures is studied by combining wide-angle X-ray diffraction and small-angle X-ray scattering. Results show that stretching can induce mesophase to crystallize into α-phase or promote this phase transformation synergistically with temperature, which depends on the selection of stretching temperature. When the temperature is lower than the glass transition temperature of rigid amorphous fraction (RAF), stress could make RAF devitrify firstly and then induce meso-α phase transition during the strain-softening process. As the temperature increases, the high temperature could induce meso-α phase transition to occur before the strain softening, while stretching could promote this transition. When the temperature is higher than a critical value around 100°C, the mesophase can be transformed into α-phase completely during stretching. SAXS results show that all the transformed α-crystal exhibits nodular morphology, and they are ductile with greatly enhanced deformability. Based on the results, a reasonable mechanism of meso-α transformation in the stretching process is proposed, explaining the phase transition that goes through several different steps.
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Liu Y, Wang Y, Zhang H, Wu Y, Zhao S, Li Q, Shao C, Wang Z. Toughening of polybutene-1 with form I′ induced by rapid pressurization. CrystEngComm 2022. [DOI: 10.1039/d1ce01228b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Combined with in situ wide angle X-ray diffraction, the mechanical properties of polybutene-1 with rapid pressurization are investigated. The toughness of polybutene-1 can be improved significantly by forms I/I′ produced by rapid pressurization.
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Affiliation(s)
- Yanping Liu
- National Center for International Joint Research of Micro-nano Molding Technology, School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou, 450001, China
| | - Yingchao Wang
- National Center for International Joint Research of Micro-nano Molding Technology, School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou, 450001, China
| | - Hongyu Zhang
- National Center for International Joint Research of Micro-nano Molding Technology, School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou, 450001, China
| | - Yuewen Wu
- National Center for International Joint Research of Micro-nano Molding Technology, School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou, 450001, China
| | - Shuo Zhao
- National Center for International Joint Research of Micro-nano Molding Technology, School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou, 450001, China
| | - Qian Li
- National Center for International Joint Research of Micro-nano Molding Technology, School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou, 450001, China
| | - Chunguang Shao
- National Engineering Research Center for Advanced Polymer Processing Technology, Key Laboratory of Materials Processing and Mold, Zhengzhou University, Zhengzhou, 450002, China
| | - Zhen Wang
- National Engineering Research Center for Advanced Polymer Processing Technology, Key Laboratory of Materials Processing and Mold, Zhengzhou University, Zhengzhou, 450002, China
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Synergistic Effect of Pressurization Rate and β-Form Nucleating Agent on the Multi-Phase Crystallization of iPP. Polymers (Basel) 2021; 13:polym13172984. [PMID: 34503024 PMCID: PMC8434399 DOI: 10.3390/polym13172984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 08/29/2021] [Accepted: 08/31/2021] [Indexed: 11/16/2022] Open
Abstract
Using a homemade pressure device, we explored the synergistic effect of pressurization rate and β-form nucleating agent (β-NA) on the crystallization of an isotactic polypropylene (iPP) melt. The obtained samples were characterized by combining small angle X-ray scattering and synchrotron wide angle X-ray diffraction. It was found that the synergistic application of pressurization and β-NA enables the preparation of a unique multi-phase crystallization of iPP, including β-, γ- and/or mesomorphic phases. Pressurization rate plays a crucial role on the formation of different crystal phases. As the pressurization rate increases in a narrow range between 0.6–1.9 MPa/s, a significant competitive formation between β- and γ-iPP was detected, and their relative crystallinity are likely to be determined by the growth of the crystal. When the pressurization rate increases further, both β- and γ-iPP contents gradually decrease, and the mesophase begins to emerge once it exceeds 15.0 MPa/s, then mesomorphic, β- and γ- iPP coexist with each other. Moreover, with different β-NA contents, the best pressurization rate for β-iPP growth is the same as 1.9 MPa/s, while more β-NA just promotes the content of β-iPP under the rates lower than 1.9 MPa/s. In addition to inducing the formation of β-iPP, it shows that β-NA can also significantly promote the formation of γ-iPP in a wide pressurization rate range between 3.8 to 75 MPa/s. These results were elucidated by combining classical nucleation theory and the growth theory of different crystalline phases, and a theoretical model of the pressurization-induced crystallization is established, providing insight into understanding the multi-phase structure development of iPP.
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Zhao X, Liao T, Lu Y, Jiang Z, Men Y. Formation and Distribution of the Mesophase in Ultrasonic Micro-Injection-Molded Isotactic Polypropylene. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00077] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xintong Zhao
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022, PR China
- School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, PR China
| | - Tao Liao
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022, PR China
| | - Ying Lu
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022, PR China
| | - Zhiyong Jiang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022, PR China
| | - Yongfeng Men
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022, PR China
- School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, PR China
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Dong B, Yang X, Ji Y, Su F, Shao C, Liu C. Polymorph selection during melt crystallization of the isotactic polybutene-1 homopolymer depending on the melt state and crystallization pressure. SOFT MATTER 2020; 16:9074-9082. [PMID: 32909580 DOI: 10.1039/d0sm01231a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This work investigated the crystalline forms obtained from melt crystallization in the isotactic polybutene-1 (iPB-1) homopolymer via manipulation of the temperature at which samples were melted (Tmelt) and crystallization pressure (Pcry). Unlike the results under atmospheric conditions where the molten sample crystallized into the pure form II and the crystallization temperature and kinetics were affected obviously by Tmelt, the melted sample crystallized into forms II or I' under high pressure, depending on Tmelt and Pcry. The content of form I' decreases with increasing Tmelt or decreasing Pcry. Meanwhile, the critical pressure for the formation of pure form I' increases with increasing Tmelt. The formation of form I' is attributed to the memory effect of the melt which preserved some ordered sequence of crystal and the high pressure (Pcry) which suppressed the nucleation and growth of the kinetically favored form II, which results in the formation of form I'. In addition, the melt crystallized form II transforms to form I under high pressure conditions; thus forms I, I' and II are observed. The relative contents of the three crystalline forms on samples for different Tmelt and Pcry are obtained in this work. The result shows that the crystalline forms in melt crystallization of iPB-1 can be customized by regulating the melt state and crystallization conditions.
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Affiliation(s)
- Beibei Dong
- National Engineering Research Center for Advanced Polymer Processing Technology, The Key Laboratory of Material Processing and Mold of Ministry of Education, College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450002, China.
| | - Xiaokang Yang
- National Engineering Research Center for Advanced Polymer Processing Technology, The Key Laboratory of Material Processing and Mold of Ministry of Education, College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450002, China.
| | - Youxin Ji
- National Engineering Research Center for Advanced Polymer Processing Technology, The Key Laboratory of Material Processing and Mold of Ministry of Education, College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450002, China.
| | - Fengmei Su
- National Engineering Research Center for Advanced Polymer Processing Technology, The Key Laboratory of Material Processing and Mold of Ministry of Education, College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450002, China.
| | - Chunguang Shao
- National Engineering Research Center for Advanced Polymer Processing Technology, The Key Laboratory of Material Processing and Mold of Ministry of Education, College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450002, China.
| | - Chuntai Liu
- National Engineering Research Center for Advanced Polymer Processing Technology, The Key Laboratory of Material Processing and Mold of Ministry of Education, College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450002, China.
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Li X, Chen P, Ding J, Zheng K, Chen L, Tian X. Rapid phase transition of polybutene-1 from form II to form I induced by pressure. POLYMER 2020. [DOI: 10.1016/j.polymer.2020.122169] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Li X, Jia W, Dong B, Yuan H, Su F, Wang Z, Wang Y, Liu C, Shen C, Shao C. Structure and Mechanical Properties of Multi-Walled Carbon Nanotubes-Filled Isotactic Polypropylene Composites Treated by Pressurization at Different Rates. Polymers (Basel) 2019; 11:polym11081294. [PMID: 31382397 PMCID: PMC6723393 DOI: 10.3390/polym11081294] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 07/12/2019] [Accepted: 07/15/2019] [Indexed: 11/24/2022] Open
Abstract
Isotactic polypropylene filled with 1 wt.% multi-walled carbon nanotubes (iPP/MWCNTs) were prepared, and their crystallization behavior induced by pressurizing to 2.0 GPa with adjustable rates from 2.5 to 1.3 × 104 MPa/s was studied. The obtained samples were characterized by combining wide angle X-ray diffraction, small angle X-ray scattering, differential scanning calorimetry, transmission electron microscopy and atomic force microscopy techniques. It was found that pressurization is a simple way to prepare iPP/MWCNTs composites in mesophase, γ-phase, or their blends. Two threshold pressurization rates marked as R1 and R2 were identified, while R1 corresponds to the onset of mesomorphic iPP formation. When the pressurization rate is lower than R1 only γ-phase generates, with its increasing mesophase begins to generate and coexist with γ-phase, and if it exceeds R2 only mesophase can generate. When iPP/MWCNTs crystallized in γ-phase, compared with the neat iPP, the existence of MWCNTs can promote the nucleation of γ-phase, leading to the formation of γ-crystal with thicker lamellae. If iPP/MWCNTs solidified in mesophase, MWCNTs can decrease the growth rate of the nodular structure, leading to the formation of mesophase with smaller nodular domains (about 9.4 nm). Mechanical tests reveal that, γ-iPP/MWCNTs composites prepared by slow pressurization display high Young’s modulus, high yield strength and high elongation at break, and meso-iPP/MWCNTs samples have excellent deformability because of the existence of nodular morphology. In this sense, the pressurization method is proved to be an efficient approach to regulate the crystalline structure and the properties of iPP/MWCNTs composites.
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Affiliation(s)
- Xiaoting Li
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Wenxia Jia
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Beibei Dong
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Huan Yuan
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Fengmei Su
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Zhen Wang
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Yaming Wang
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Chuntai Liu
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Changyu Shen
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Chunguang Shao
- Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China.
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