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Gonçalves LFFF, Reis RL, Fernandes EM. Forefront Research of Foaming Strategies on Biodegradable Polymers and Their Composites by Thermal or Melt-Based Processing Technologies: Advances and Perspectives. Polymers (Basel) 2024; 16:1286. [PMID: 38732755 PMCID: PMC11085284 DOI: 10.3390/polym16091286] [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: 01/12/2024] [Revised: 04/13/2024] [Accepted: 04/26/2024] [Indexed: 05/13/2024] Open
Abstract
The last few decades have witnessed significant advances in the development of polymeric-based foam materials. These materials find several practical applications in our daily lives due to their characteristic properties such as low density, thermal insulation, and porosity, which are important in packaging, in building construction, and in biomedical applications, respectively. The first foams with practical applications used polymeric materials of petrochemical origin. However, due to growing environmental concerns, considerable efforts have been made to replace some of these materials with biodegradable polymers. Foam processing has evolved greatly in recent years due to improvements in existing techniques, such as the use of supercritical fluids in extrusion foaming and foam injection moulding, as well as the advent or adaptation of existing techniques to produce foams, as in the case of the combination between additive manufacturing and foam technology. The use of supercritical CO2 is especially advantageous in the production of porous structures for biomedical applications, as CO2 is chemically inert and non-toxic; in addition, it allows for an easy tailoring of the pore structure through processing conditions. Biodegradable polymeric materials, despite their enormous advantages over petroleum-based materials, present some difficulties regarding their potential use in foaming, such as poor melt strength, slow crystallization rate, poor processability, low service temperature, low toughness, and high brittleness, which limits their field of application. Several strategies were developed to improve the melt strength, including the change in monomer composition and the use of chemical modifiers and chain extenders to extend the chain length or create a branched molecular structure, to increase the molecular weight and the viscosity of the polymer. The use of additives or fillers is also commonly used, as fillers can improve crystallization kinetics by acting as crystal-nucleating agents. Alternatively, biodegradable polymers can be blended with other biodegradable polymers to combine certain properties and to counteract certain limitations. This work therefore aims to provide the latest advances regarding the foaming of biodegradable polymers. It covers the main foaming techniques and their advances and reviews the uses of biodegradable polymers in foaming, focusing on the chemical changes of polymers that improve their foaming ability. Finally, the challenges as well as the main opportunities presented reinforce the market potential of the biodegradable polymer foam materials.
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Affiliation(s)
- Luis F. F. F. Gonçalves
- 3B’s Research Group, I3Bs–Research Institute on Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, Parque de Ciência e Tecnologia, Zona Industrial da Gandra, Barco, 4805-017 Guimarães, Portugal;
- ICVS/3B’s—PT Government Associate Laboratory, Barco, 4805-017 Guimarães, Portugal
| | - Rui L. Reis
- 3B’s Research Group, I3Bs–Research Institute on Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, Parque de Ciência e Tecnologia, Zona Industrial da Gandra, Barco, 4805-017 Guimarães, Portugal;
- ICVS/3B’s—PT Government Associate Laboratory, Barco, 4805-017 Guimarães, Portugal
| | - Emanuel M. Fernandes
- 3B’s Research Group, I3Bs–Research Institute on Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, Parque de Ciência e Tecnologia, Zona Industrial da Gandra, Barco, 4805-017 Guimarães, Portugal;
- ICVS/3B’s—PT Government Associate Laboratory, Barco, 4805-017 Guimarães, Portugal
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2
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Yang H, Du J. Crystallinity, Rheology, and Mechanical Properties of Low-/High-Molecular-Weight PLA Blended Systems. Molecules 2023; 29:169. [PMID: 38202753 PMCID: PMC10780580 DOI: 10.3390/molecules29010169] [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: 11/17/2023] [Revised: 12/22/2023] [Accepted: 12/25/2023] [Indexed: 01/12/2024] Open
Abstract
As semi-crystalline polyester (lactic acid) (PLA) is combined with other reinforcing materials, challenges such as phase separation, environmental pollution, and manufacturing difficulties could hinder the benefits of PLA, including complete biodegradability and strong mechanical properties. In the present investigation, melt blending is utilized to establish a mixture of low- and high-molecular-weight polylactic acids (LPLA and HPLA). The crystallinity, rheology, and mechanical properties of the combination were analyzed using rotational rheometry, differential scanning calorimetry, X-ray diffraction, polarized optical microscopy, scanning electron microscopy, and universal testing equipment. The results demonstrate compatibility between LPLA and HPLA. Moreover, an increase in LPLA concentration leads to a decrease in the crystallization rate, spherulite size, fractional crystallinity, and XRD peak intensity during isothermal crystallization. LPLA acts as a diluent during isothermal crystallization, whereas HPLA functions as a nucleating agent in the non-isothermal crystallization process, promoting the growth of LPLA crystals and leading to co-crystallization. The blended system with a 5% LPLA mass fraction exhibits the highest tensile strength and enhances rheological characteristics. By effectively leveraging the relationship between various molecular weights of PLA's mechanical, rheological, and crystallization behavior, this scrutiny improves the physical and mechanical characteristics of the material, opening up new opportunities.
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Affiliation(s)
- Hongwei Yang
- School of Materials Science & Engineering, North Minzu University, Yinchuan 750021, China
| | - Jianghua Du
- School of Materials Science & Engineering, North Minzu University, Yinchuan 750021, China
- Key Laboratory of Polymer Materials & Manufacturing Technology, North Minzu University, Yinchuan 750021, China
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3
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Open-Celled Foams from Polyethersulfone/Poly(Ethylene Glycol) Blends Using Foam Extrusion. Polymers (Basel) 2022; 15:polym15010118. [PMID: 36616468 PMCID: PMC9824152 DOI: 10.3390/polym15010118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 12/16/2022] [Accepted: 12/22/2022] [Indexed: 12/29/2022] Open
Abstract
Polyethersulfone (PESU), as both a pristine polymer and a component of a blend, can be used to obtain highly porous foams through batch foaming. However, batch foaming is limited to a small scale and is a slow process. In our study, we used foam extrusion due to its capacity for large-scale continuous production and deployed carbon dioxide (CO2) and water as physical foaming agents. PESU is a high-temperature thermoplastic polymer that requires processing temperatures of at least 320 °C. To lower the processing temperature and obtain foams with higher porosity, we produced PESU/poly(ethylene glycol) (PEG) blends using material penetration. In this way, without the use of organic solvents or a compounding extruder, a partially miscible PESU/PEG blend was prepared. The thermal and rheological properties of homopolymers and blends were characterized and the CO2 sorption performance of selected blends was evaluated. By using these blends, we were able to significantly reduce the processing temperature required for the extrusion foaming process by approximately 100 °C without changing the duration of processing. This is a significant advancement that makes this process more energy-efficient and sustainable. Additionally, the effects of blend composition, nozzle temperature and foaming agent type were investigated, and we found that higher concentrations of PEG, lower nozzle temperatures, and a combination of CO2 and water as the foaming agent delivered high porosity. The optimum blend process settings provided foams with a porosity of approximately 51% and an average foam cell diameter of 5 µm, which is the lowest yet reported for extruded polymer foams according to the literature.
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4
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Li P, Lan B, Zhang Q, Yang Q, Gong P, Park CB, Li G. Microcellular foams simultaneous reinforcing and toughening strategy of combining nano-fibrillation network and supercritical solid-state foaming. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.124928] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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5
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Albuquerque RQ, Brütting C, Standau T, Ruckdäschel H. A machine learning investigation of low-density polylactide batch foams. E-POLYMERS 2022. [DOI: 10.1515/epoly-2022-0031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Abstract
Developing novel foams with tailored properties is a challenge. If properly addressed, efficient screening can potentially accelerate material discovery and reduce material waste, improving sustainability and efficiency in the development phase. In this work, we address this problem using a hybrid experimental and theoretical approach. Machine learning (ML) models were trained to predict the density of polylactide (PLA) foams based on their processing parameters. The final ML ensemble model was a linear combination of gradient boosting, random forest, kernel ridge, and support vector regression models. Comparison of the actual and predicted densities of PLA systems resulted in a mean absolute error of 30 kg·m−3 and a coefficient of determination (R
2) of 0.94. The final ensemble model was then used to explore the ranges of predicted density in the space of processing parameters (temperature, pressure, and time) and to suggest some parameter sets that could lead to low-density PLA foams. The new PLA foams were produced and showed experimental densities in the range of 36–48 kg·m−3, which agreed well with the corresponding predicted values, which ranged between 38 and 54 kg·m−3. The experimental–theoretical procedure described here could be applied to other materials and pave the way to more sustainable and efficient foam development processes.
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Affiliation(s)
- Rodrigo Q. Albuquerque
- Department of Polymer Engineering, University of Bayreuth, Universitätsstraße 30 , 95447 Bayreuth , Germany
- Neue Materialien Bayreuth GmbH, Gottlieb-Keim-Straße 60 , 95448 Bayreuth , Germany
| | - Christian Brütting
- Department of Polymer Engineering, University of Bayreuth, Universitätsstraße 30 , 95447 Bayreuth , Germany
| | - Tobias Standau
- Department of Polymer Engineering, University of Bayreuth, Universitätsstraße 30 , 95447 Bayreuth , Germany
| | - Holger Ruckdäschel
- Department of Polymer Engineering, University of Bayreuth, Universitätsstraße 30 , 95447 Bayreuth , Germany
- Neue Materialien Bayreuth GmbH, Gottlieb-Keim-Straße 60 , 95448 Bayreuth , Germany
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Jiang YY, Ren L, Wu GH, Guo W, Guan XF, Zhang MY, Zhang HX. An environmentally sustainable isosorbide-based plasticizer for biodegradable poly(butylene succinate). JOURNAL OF POLYMER ENGINEERING 2022. [DOI: 10.1515/polyeng-2021-0232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
In this article, isosorbide divalerate (SDV), an alternative renewable resource plasticizer for degradable poly(butylene succinate) (PBS) was successfully synthesized with isosorbide and valeric acid, and was characterized by Fourier transform infrared (FTIR). The mechanical properties, glass transition temperature (T
g
), crystallization properties, rheological behavior of PBS/SDV blends was studied in detail. The results showed that incorporation of SDV had successfully reduced T
g
of the PBS composites, particularly at 20 wt% SDV, where the value of T
g
exhibited a reduction of 12 °C or 39% compared to pure PBS, demonstrating SDV possessed plasticizing efficacy. The crystallinity of PBS was declined by presence of SDV in the blends, and the incorporation of 20 wt% SDV into PBS matrix promoted an impressive decrease of exceeding 22%. Significant enhancement of the toughness and flexibility of PBS was achieved by the addition of SDV. The rheological test revealed that the decrease of modulus and viscosity improved the processing properties of the materials, which broadened the PBS applications. Altogether the SEM showed the fracture surface of the composites undergoes a brittle-tough transition with increasing SDV content below 12% content, meanwhile, significant phase separation was observed in the composites with high content of SDV.
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Affiliation(s)
- Ying Yong Jiang
- National Engineering Laboratory for Polymer Materials Synthesis and Application Technology, Changchun University of Technology , Changchun 130012 , China
- School of Chemical Engineering, Changchun University of Technology , Changchun 130012 , China
| | - Liang Ren
- National Engineering Laboratory for Polymer Materials Synthesis and Application Technology, Changchun University of Technology , Changchun 130012 , China
- School of Chemical Engineering, Changchun University of Technology , Changchun 130012 , China
| | - Gui Hui Wu
- National Engineering Laboratory for Polymer Materials Synthesis and Application Technology, Changchun University of Technology , Changchun 130012 , China
- School of Chemical Engineering, Changchun University of Technology , Changchun 130012 , China
| | - Wei Guo
- National Engineering Laboratory for Polymer Materials Synthesis and Application Technology, Changchun University of Technology , Changchun 130012 , China
- School of Chemical Engineering, Changchun University of Technology , Changchun 130012 , China
| | - Xian Feng Guan
- National Engineering Laboratory for Polymer Materials Synthesis and Application Technology, Changchun University of Technology , Changchun 130012 , China
- School of Chemical Engineering, Changchun University of Technology , Changchun 130012 , China
| | - Ming Yao Zhang
- National Engineering Laboratory for Polymer Materials Synthesis and Application Technology, Changchun University of Technology , Changchun 130012 , China
- School of Chemical Engineering, Changchun University of Technology , Changchun 130012 , China
| | - Hui Xuan Zhang
- National Engineering Laboratory for Polymer Materials Synthesis and Application Technology, Changchun University of Technology , Changchun 130012 , China
- School of Chemical Engineering, Changchun University of Technology , Changchun 130012 , China
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7
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Approach to quantify the resistance of polymeric foams against thermal load under compression. JOURNAL OF POLYMER ENGINEERING 2022. [DOI: 10.1515/polyeng-2021-0312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Nowadays, numerous techniques are used to quantify the resistance of cellular polymers against a thermal load. These techniques differ in significance and reproducibility and are all dependent on foam density, structure (i.e., cell size and -distribution) and sample geometry. Very different behaviors are expected for extrusion- and bead foams, as well as for amorphous and semi-crystalline polymers. Moreover, established tests use temperature ramps which would lead to temperature gradients within the sample and thus to faulty results. In this study, we developed a new approach from an engineering perspective to minimize these influences. In this approach, the resistance against the thermal load is derived from a steady creep test with defined temperature steps under a mechanical load, which is specifically set for each foam sample depending on its static compression behavior at room temperature. The two-stage test therefore combines (i) a standard quasi-static compression test at room temperature and (ii) a creep test with stepwise increased thermal loading. For each foam type, a rather low mechanical load (stress) is determined from the quasi-static compression test at room temperature; low enough to remain below the collapse strength and avoid irreversible deformation (i.e., buckling and/or breaking of the cell walls). This load is then applied in a creep test where the temperature is increased in defined steps from room temperature to a temperature close to T
g
or T
m
. The stepwise increase and holding of the temperature for a defined time enables a homogeneous temperature in the test specimen. The approach was applied to (i) polystyrene extrusion and bead foams (i.e., XPS and EPS), which have different foam structure, (ii) amorphous and semi-crystalline bead foams of polystyrene (EPS) and polypropylene (EPP), (iii) bead foams with different densities (30, 60, 120, and 210 kg/m3) and (iv) to a new type of bead foam made of the engineering polymer polybutylene terephthalate (E-PBT). The termination criterion for the test is defined as the temperature at which a relative compression of 10% is reached in the creep test with temperature steps. We suggest calling it the heat stability temperature T
HS. For the studied foams, the procedure delivers characteristic T
HS values that allow a good comparison between different polymer matrices and densities. The heat stability temperature T
HS of amorphous PS foams (i.e., XPS and EPS) was determined to be 98 °C, which is close to the glass transition temperature T
g
. Using the same approach, values of 99–107 °C were determined for EPP and 186 °C for the semi-crystalline bead foam E-PBT.
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8
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Standau T, Nofar M, Dörr D, Ruckdäschel H, Altstädt V. A Review on Multifunctional Epoxy-Based Joncryl® ADR Chain Extended Thermoplastics. POLYM REV 2021. [DOI: 10.1080/15583724.2021.1918710] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Tobias Standau
- Department of Polymer Engineering, University of Bayreuth, Bayreuth, Germany
| | - Mohammadreza Nofar
- Metallurgical and Materials Engineering, Department Faculty of Chemical and Metallurgical Engineering, Istanbul Technical University, Maslak, Istanbul, Turkey
- Polymer Science and Technology Program, Institute of Science and Technology, Istanbul Technical University, Maslak, Istanbul, Turkey
| | - Dominik Dörr
- Department of Polymer Engineering, University of Bayreuth, Bayreuth, Germany
| | - Holger Ruckdäschel
- Department of Polymer Engineering, University of Bayreuth, Bayreuth, Germany
| | - Volker Altstädt
- Department of Polymer Engineering, University of Bayreuth, Bayreuth, Germany
- Bavarian Polymer Institute and Bayreuth Institute of Macromolecular Research, University of Bayreuth, Bayreuth, Germany
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9
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Venkatesan KB, Karkhanis SS, Matuana LM. Microcellular foaming of poly(lactic acid) branched with food‐grade chain extenders. J Appl Polym Sci 2021. [DOI: 10.1002/app.50686] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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10
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Synthesis of flexible poly(l-lactide)-b-polyethylene glycol-b-poly(l-lactide) bioplastics by ring-opening polymerization in the presence of chain extender. E-POLYMERS 2020. [DOI: 10.1515/epoly-2020-0047] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractPoly(l-lactide)-b-polyethylene glycol-b-poly(l-lactide) (PLLA-PEG-PLLA) is found to be more flexible than PLLA due to the flexibility of PEG middle blocks. Melt flow and mechanical properties of PLLA-PEG-PLLA were improved through post melt blending with a chain extender (CE). In this work, in situ chain-extended PLLA-PEG-PLLAs were synthesized by ring-opening polymerization in the presence of Joncryl® CE. The influence of CE content (1.0, 2.0, and 4.0 phr) on the gel content, melt flow index (MFI), thermal properties, and mechanical properties of the obtained in situ chain-extended PLLA-PEG-PLLAs was investigated. The gel content of in situ chain-extended PLLA-PEG-PLLA increased while the MFI and degree of crystallinity significantly decreased with increasing CE content. The in situ chain-extended PLLA-PEG-PLLA with 1.0 phr CE showed the best tensile properties. The extensibility of in situ chain-extended PLLA-PEG-PLLA films decreased when the CE contents were higher than 1.0 phr. These in situ chain-extended PLLA-PEG-PLLA films can be used as highly flexible bioplastics.
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11
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Dörr D, Standau T, Murillo Castellón S, Bonten C, Altstädt V. Rheology in the Presence of Carbon Dioxide (CO 2) to Study the Melt Behavior of Chemically Modified Polylactide (PLA). Polymers (Basel) 2020; 12:polym12051108. [PMID: 32414010 PMCID: PMC7285241 DOI: 10.3390/polym12051108] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/06/2020] [Accepted: 05/12/2020] [Indexed: 11/21/2022] Open
Abstract
For the preparation of polylactide (PLA)-based foams, it is commonly necessary to increase the melt strength of the polymer. Additives such as chain extenders (CE) or peroxides are often used to build up the molecular weight by branching or even crosslinking during reactive extrusion. Furthermore, a blowing agent with a low molecular weight, such as carbon dioxide (CO2), is introduced in the foaming process, which might affect the reactivity during extrusion. Offline rheological tests can help to measure and better understand the kinetics of the reaction, especially the reaction between the polymer and the chemical modifier. However, rheological measurements are mostly done in an inert nitrogen atmosphere without an equivalent gas loading of the polymer melt, like during the corresponding reactive extrusion process. Therefore, the influence of the blowing agent itself is not considered within these standard rheological measurements. Thus, in this study, a rheometer equipped with a pressure cell is used to conduct rheological measurements of neat and chemical-modified polymers in the presence of CO2 at pressures up to 40 bar. The specific effects of CO2 at elevated pressure on the reactivity between the polymer and the chemical modifiers (an organic peroxide and as second choice, an epoxy-based CE) were investigated and compared. It could be shown in the rheological experiments that the reactivity of the chain extender is reduced in the presence of CO2, while the peroxide is less affected. Finally, it was possible to detect the recrystallization temperature Trc of the unmodified and unbranched sample by the torque maximum in the rheometer, representing the tear off of the stamp from the sample. Trc was about 13 K lower in the CO2-loaded sample. Furthermore, it was possible to detect the influences of branching and gas loading simultaneously. Here the influence of the branching on Trc was much higher in comparison to a gas loading.
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Affiliation(s)
- Dominik Dörr
- Department of Polymer Engineering, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany; (D.D.); (T.S.)
| | - Tobias Standau
- Department of Polymer Engineering, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany; (D.D.); (T.S.)
| | - Svenja Murillo Castellón
- Institut für Kunststofftechnik, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany; (S.M.C.); (C.B.)
| | - Christian Bonten
- Institut für Kunststofftechnik, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany; (S.M.C.); (C.B.)
| | - Volker Altstädt
- Department of Polymer Engineering, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany; (D.D.); (T.S.)
- Bavarian Polymer Institute, Universitätsstraße 30, 95447 Bayreuth, Germany
- Correspondence: ; Tel.: +49-921-55-7471
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12
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Evaluation of the Zero Shear Viscosity, the D-Content and Processing Conditions as Foam Relevant Parameters for Autoclave Foaming of Standard Polylactide (PLA). MATERIALS 2020; 13:ma13061371. [PMID: 32197473 PMCID: PMC7143153 DOI: 10.3390/ma13061371] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 03/13/2020] [Accepted: 03/16/2020] [Indexed: 11/16/2022]
Abstract
In this comprehensive study, the influence of (i) material specific properties (e.g., molecular weight, zero shear viscosity, D-content) and (ii) process parameters (e.g., saturation temperature, -time, -pressure, and pressure drop rate) on the expansion behavior during the autoclave foaming process were investigated on linear Polylactide (PLA) grades, to identify and evaluate the foam relevant parameters. Its poor rheological behavior is often stated as a drawback of PLA, that limits its foamability. Therefore, nine PLA grades with different melt strength and zero shear viscosity were systematically chosen to identify whether these are the main factors governing the foam expansion and whether there is a critical value for these rheological parameters to be exceeded, to achieve low density foams with fine cells. With pressure drop induced batch foaming experiments, it could be shown that all of the investigated PLA grades could be foamed without the often used chemical modifications, although with different degrees of expansion. Interestingly, PLAs foaming behavior is rather complex and can be influenced by many other factors due to its special nature. A low molecular weight combined with a high ability to crystallize only lead to intermediate density reduction. In contrast, a higher molecular weight (i.e., increased zero shear viscosity) leads to significant increased expandability independent from the D-content. However, the D-content plays a crucial role in terms of foaming temperature and crystallization. Furthermore, the applied process parameters govern foam expansion, cell size and crystallization.
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13
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Bethke C, Goedderz D, Weber L, Standau T, Döring M, Altstädt V. Improving the flame‐retardant property of bottle‐grade PET foam made by reactive foam extrusion. J Appl Polym Sci 2020. [DOI: 10.1002/app.49042] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Christian Bethke
- Department of Polymer EngineeringUniversity of Bayreuth Bayreuth Germany
| | - Daniela Goedderz
- Fraunhofer Institute for Structural Durability and System Reliability LBF Darmstadt Germany
- Ernst‐Berl Institute for Chemical Engineering and Macromolecular Science, Technische Universität Darmstadt Darmstadt Germany
| | - Lais Weber
- Fraunhofer Institute for Structural Durability and System Reliability LBF Darmstadt Germany
- Ernst‐Berl Institute for Chemical Engineering and Macromolecular Science, Technische Universität Darmstadt Darmstadt Germany
| | - Tobias Standau
- Department of Polymer EngineeringUniversity of Bayreuth Bayreuth Germany
| | - Manfred Döring
- Fraunhofer Institute for Structural Durability and System Reliability LBF Darmstadt Germany
| | - Volker Altstädt
- Department of Polymer EngineeringUniversity of Bayreuth Bayreuth Germany
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14
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Standau T, Zhao C, Murillo Castellón S, Bonten C, Altstädt V. Chemical Modification and Foam Processing of Polylactide (PLA). Polymers (Basel) 2019; 11:E306. [PMID: 30960290 PMCID: PMC6419231 DOI: 10.3390/polym11020306] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 02/06/2019] [Accepted: 02/07/2019] [Indexed: 11/16/2022] Open
Abstract
Polylactide (PLA) is known as one of the most promising biopolymers as it is derived from renewable feedstock and can be biodegraded. During the last two decades, it moved more and more into the focus of scientific research and industrial use. It is even considered as a suitable replacement for standard petroleum-based polymers, such as polystyrene (PS), which can be found in a wide range of applications-amongst others in foams for packaging and insulation applications-but cause strong environmental issues. PLA has comparable mechanical properties to PS. However, the lack of melt strength is often referred to as a drawback for most foaming processes. One way to overcome this issue is the incorporation of chemical modifiers which can induce chain extension, branching, or cross-linking. As such, a wide variety of substances were studied in the literature. This work should give an overview of the most commonly used chemical modifiers and their effects on rheological, thermal, and foaming behavior. Therefore, this review article summarizes the research conducted on neat and chemically modified PLA foamed with the conventional foaming methods (i.e., batch foaming, foam extrusion, foam injection molding, and bead foaming).
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Affiliation(s)
- Tobias Standau
- Depatment of Polymer Engineering, University Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
| | - Chunjing Zhao
- Depatment of Polymer Engineering, University Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
| | - Svenja Murillo Castellón
- Institut für Kunststofftechnik, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany.
| | - Christian Bonten
- Institut für Kunststofftechnik, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany.
| | - Volker Altstädt
- Depatment of Polymer Engineering, University Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
- Bavarian Polymer Institute and Bayreuth Institute of Macromolecular Research, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
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