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Huang PW, Peng HS, Hwang SJ, Huang CT. Study on the Flow, Foaming Characteristics and Structural Strength of Polypropylene Structural Foam Injection Molding by Innovative Nitrogen and Molten Plastic Mixing Mechanism. Polymers (Basel) 2023; 15:polym15092116. [PMID: 37177261 PMCID: PMC10180833 DOI: 10.3390/polym15092116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 04/21/2023] [Accepted: 04/27/2023] [Indexed: 05/15/2023] Open
Abstract
Plastic foam molding methods include thermoforming, extrusion and injection molding. Injection foam molding is a one-time molding method with high production efficiency and good product quality. It is suitable for foamed plastic products with complex shapes and strict size requirements. It is also the main method for producing structural bubbles. In this investigation, we developed a structural foam injection molding technology using the gas supply equipment connected to the unique plasticizing mechanism of the injection machine and studied its influence on the specimens' melt rheology quality and foam structures. In the experiment, the forming material was polypropylene (PP), and the gas for mixing/forming foaming characteristics was nitrogen (N2). Additionally, in order to observe the rheological properties of N2/melt mixing, a melt flow specimen mold cavity was designed and the change in the melt viscosity index was observed using a melt pressure sensing element installed at the nozzle position. With the nitrogen supply equipment connected to a unique plasticizing mechanism, the mixing of gas and molten plastic can be achieved at the screw plasticizing stage, where the foaming effect is realized during the melt-filling process due to the thermodynamic instability of the gas. It was also found that an increase in N2 fill content increased melt fluidity, and the trend of melt pressure and melt viscosity index showed that the higher the gas content, the lower the trend. The foaming characteristic depends on the gas thermodynamic instability and the pressure release, so it can be seen from the melt fill path that, the greater the pressure near the gate, the lower the foaming amount and the internal structure (SEM) after molding; the farther from the gate, the greater the relative increase in the foaming growth/amount. This phenomenon will be more obvious when the N2 fill content is increased.
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Affiliation(s)
- Po-Wei Huang
- Program of Mechanical and Aeronautical Engineering, Feng Chia University of Engineering and Science, Taichung 407102, Taiwan
| | - Hsin-Shu Peng
- Department of Mechanical and Computer Aided Engineering, Feng Chia University of Engineering and Science, Taichung 407102, Taiwan
| | - Sheng-Jye Hwang
- Department of Mechanical Engineering, National Cheng Kung University of Engineering, Tainan 70101, Taiwan
| | - Chao-Tsai Huang
- Department of Chemical and Materials Engineering, Tamkang University of Engineering, New Taipei City 251301, Taiwan
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2
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Song T, Liu M, Tian J, Wang S, Li Q. Effect of PLA/TiO2/Lg filler competition and synergy on crystallization behavior, mechanics and functionality of composite foaming materials. POLYMER 2023. [DOI: 10.1016/j.polymer.2023.125797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
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3
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Rangappa R, Yeh SK. Effect of N2 plasticization on the crystallization of different hardnesses of thermoplastic polyurethanes. J Supercrit Fluids 2022. [DOI: 10.1016/j.supflu.2022.105726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Sandino C, Peuvrel-Disdier E, Agassant JF, Laure P, Boyer SAE, Hibert G, Trolez Y. Extrusion foaming of linear and branched polypropylenes – input of the thermomechanical analysis of pressure drop in the die. INT POLYM PROC 2022. [DOI: 10.1515/ipp-2022-0025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
This paper aims at a better understanding of the polypropylene (PP) physical extrusion foaming process with the objective of obtaining the lowest possible foam density. Two branched PPs were compared to the corresponding linear ones. Their shear and elongation viscosities were measured as well as their crystalline properties. Trials were conducted in a single screw extruder equipped with a gear pump and a static mixer cooler to adjust the melt temperature at the final die. The effect of decreasing this temperature on the PP foamability and on the pressure drop in the die was analyzed. The foam density of branched PPs varies from high to low values while decreasing the foaming temperature. In the same processing conditions, the foam density of linear PPs does not decrease so much, as already evidenced in the literature. The foamability transition coincides with an increase of the pressure drop in the die. The originality of the work lies in the thermomechanical analysis of the polymer flow in the die which allows the identification of the relevant physical phenomena for a good foamability. The comparison of the experimental pressure drops in the die and the computed ones with the identified purely viscous behavior points out the influence of the foaming temperature and of the PP structure. At high foaming temperature the discrepancy between experimental measurements and the computed pressure drops remains limited. It increases when decreasing the foaming temperature, but the mismatch is much more important for branched PPs than for linear ones. This difference is analyzed as a combination of the activation energy of the viscosity, the elongational viscosity in the convergent geometry of the die which is much more important for branched PPs than for linear ones, and the onset of crystallization which occurs at higher temperature for branched PPs than for linear PPs.
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Affiliation(s)
- Carlos Sandino
- Mines Paris, PSL University , Centre de mise en forme des matériaux (CEMEF), CNRS UMR 7635, CS 10207, 06904 Sophia Antipolis cedex , France
| | - Edith Peuvrel-Disdier
- Mines Paris, PSL University , Centre de mise en forme des matériaux (CEMEF), CNRS UMR 7635, CS 10207, 06904 Sophia Antipolis cedex , France
| | - Jean-François Agassant
- Mines Paris, PSL University , Centre de mise en forme des matériaux (CEMEF), CNRS UMR 7635, CS 10207, 06904 Sophia Antipolis cedex , France
| | - Patrice Laure
- Mines Paris, PSL University , Centre de mise en forme des matériaux (CEMEF), CNRS UMR 7635, CS 10207, 06904 Sophia Antipolis cedex , France
- Laboratoire J.-A. Dieudonné, CNRS UMR 6621 , Université Côte d’Azur , Parc Valrose, 06108 Nice Cedex 02 , France
| | - Séverine A. E. Boyer
- Mines Paris, PSL University , Centre de mise en forme des matériaux (CEMEF), CNRS UMR 7635, CS 10207, 06904 Sophia Antipolis cedex , France
| | - Geoffrey Hibert
- TotalEnergies One Tech Belgium , Zone Industrielle Feluy C, B 7181 Feluy , Belgium
| | - Yves Trolez
- TotalEnergies One Tech Belgium , Zone Industrielle Feluy C, B 7181 Feluy , Belgium
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Kweon MS, Embabi M, Shivokhin ME, Gupta A, Yan X, Pehlert G, Lee PC. Tuning High and Low Temperature Foaming Behavior of Linear and Long-Chain Branched Polypropylene via Partial and Complete Melting. Polymers (Basel) 2021; 14:polym14010044. [PMID: 35012070 PMCID: PMC8747320 DOI: 10.3390/polym14010044] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/13/2021] [Accepted: 12/20/2021] [Indexed: 11/16/2022] Open
Abstract
While existing foam studies have identified processing parameters, such as high-pressure drop rate, and engineering measures, such as high melt strength, as key factors for improving foamability, there is a conspicuous absence of studies that directly relate foamability to material properties obtained from fundamental characterization. To bridge this gap, this work presents batch foaming studies on one linear and two long-chain branched polypropylene (PP) resins to investigate how foamability is affected by partial melting (Method 1) and complete melting followed by undercooling (Method 2). At temperatures above the melting point, similar expansion was obtained using both foaming procedures within each resin, while the PP with the highest strain hardening ratio (13) exhibited the highest expansion ratio (45 ± 3). At low temperatures, the foamability of all resins was dramatically improved using Method 2 compared to Method 1, due to access to lower foaming temperatures (<150 °C) near the crystallization onset. Furthermore, Method 2 resulted in a more uniform cellular structure over a wider temperature range (120–170 °C compared to 155–175 °C). Overall, strong extensional hardening and low onset of crystallization were shown to give rise to foamability at high and low temperatures, respectively, suggesting that both characteristics can be appropriately used to tune the foamability of PP in industrial foaming applications.
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Affiliation(s)
- Mu Sung Kweon
- Multifunctional Composites Manufacturing Laboratory (MCML), Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON M5S 3G8, Canada; (M.S.K.); (M.E.)
| | - Mahmoud Embabi
- Multifunctional Composites Manufacturing Laboratory (MCML), Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON M5S 3G8, Canada; (M.S.K.); (M.E.)
| | - Maksim E. Shivokhin
- ExxonMobil Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA; (M.E.S.); (A.G.); (X.Y.); (G.P.)
| | - Anvit Gupta
- ExxonMobil Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA; (M.E.S.); (A.G.); (X.Y.); (G.P.)
| | - Xuejia Yan
- ExxonMobil Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA; (M.E.S.); (A.G.); (X.Y.); (G.P.)
| | - George Pehlert
- ExxonMobil Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA; (M.E.S.); (A.G.); (X.Y.); (G.P.)
| | - Patrick C. Lee
- Multifunctional Composites Manufacturing Laboratory (MCML), Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON M5S 3G8, Canada; (M.S.K.); (M.E.)
- Correspondence: ; Tel.: +1-(416)-946-5407
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Chen J, Schneider K, Heinrich G. In-Situ Synchrotron X-ray Study on the Structure Variation of Morphology-Identified Injection-Molded β-Nucleated iPP under Tensile Deformation. Polymers (Basel) 2021; 13:polym13213730. [PMID: 34771288 PMCID: PMC8587524 DOI: 10.3390/polym13213730] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/20/2021] [Accepted: 10/24/2021] [Indexed: 11/25/2022] Open
Abstract
The deformation behavior of semi-crystalline polymers is strongly dependent on the morphology formed during processing. In this study, in-situ synchrotron X-ray was firstly used to identify the morphological distributions of injection-molded isotactic polypropylene (iPP) with different concentrations of β-nucleating agent. It was found that under relatively high concentration of β-nucleating agent (i.e., ≥0.03 wt.%), the outer region (skin and shear region) of the iPP was dominated by mainly highly oriented α-phase as well as certain amount γ-phase, while the core region was rich in β-crystals with little if any orientation. The addition of the β-nucleating agent was beneficial for the formation of lamellae with large lamellar stacking distance in the shear layer. Then the synchrotron X-ray was applied to study the structure variation of those morphology-identified samples under tensile deformation. It was found that voids and cavities along the stretching direction existed in the deformed iPP samples and their volume increased with increasing concentration of β-nucleating agent. The increased volume of void and cavity was associated with the β to α phase transition, which mainly occurred at the core region. In addition, upon stretching crystalline fragmentation and rearrangement took place following the formation of thinner lamellae.
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Affiliation(s)
- Jianhong Chen
- Fujian Provincial Key Laboratory of Functional Materials and Applications, Xiamen University of Technology, Ligong Road 600, Xiamen 361024, China
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden, Germany;
- Correspondence: (J.C.); (K.S.)
| | - Konrad Schneider
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden, Germany;
- Correspondence: (J.C.); (K.S.)
| | - Gert Heinrich
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden, Germany;
- Institut für Textilmaschinen und Textile Hochleistungswerkstofftechnik, Technische Universität Dresden, Zellescher Weg 17, 01062 Dresden, Germany
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Mendoza-Cedeno S, Kweon MS, Newby S, Shivokhin M, Pehlert G, Lee PC. Improved Cell Morphology and Surface Roughness in High-Temperature Foam Injection Molding Using a Long-Chain Branched Polypropylene. Polymers (Basel) 2021; 13:polym13152404. [PMID: 34372006 PMCID: PMC8348131 DOI: 10.3390/polym13152404] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/16/2021] [Accepted: 07/17/2021] [Indexed: 11/21/2022] Open
Abstract
Long-chain branched polypropylene (LCB PP) has been used extensively to improve cell morphologies in foaming applications. However, most research focuses on low melt flow rate (MFR) resins, whereas foam production methods such as mold-opening foam injection molding (MO-FIM) require high-MFR resins to improve processability. A systematic study was conducted comparing a conventional linear PP, a broad molecular weight distribution (BMWD) linear PP, and a newly developed BMWD LCB PP for use in MO-FIM. The effects of foaming temperature and molecular architecture on cell morphology, surface roughness, and mechanical properties were studied by utilizing two chemical blowing agents (CBAs) with different activation temperatures and varying packing times. At the highest foaming temperatures, BMWD LCB PP foams exhibited 887% higher cell density, 46% smaller cell sizes, and more uniform cell structures than BWMD linear PP. Linear PP was found to have a surface roughness 23% higher on average than other resins. The BMWD LCB PP was found to have increased flexural modulus (44%) at the cost of decreased toughness (−88%) compared to linear PP. The branched architecture and high molecular weight of the BMWD LCB PP contributed to improved foam morphologies and surface quality in high-temperature MO-FIM conditions.
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Affiliation(s)
- Steven Mendoza-Cedeno
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON M5S 3G8, Canada; (S.M.-C.); (M.S.K.)
| | - Mu Sung Kweon
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON M5S 3G8, Canada; (S.M.-C.); (M.S.K.)
| | - Sarah Newby
- ExxonMobil Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA; (S.N.); (M.S.); (G.P.)
| | - Maksim Shivokhin
- ExxonMobil Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA; (S.N.); (M.S.); (G.P.)
| | - George Pehlert
- ExxonMobil Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA; (S.N.); (M.S.); (G.P.)
| | - Patrick C. Lee
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON M5S 3G8, Canada; (S.M.-C.); (M.S.K.)
- Correspondence: ; Tel.: +1-(416)-946-5407
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