Polymer Miscibility in Supercritical Carbon Dioxide: Free Volume as a Driving Force

DeFelice, Jeffrey; Lipson, Jane E. G.

doi:10.1021/ma501199n

Cited by 15 publications

(15 citation statements)

References 46 publications

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“…As a green solvent, supercritical carbon dioxide (scCO 2 ) has found widespread use in polymer processing, including polymer blending [1], particle production [2], microcellular foaming [3,4], polymer modification [5], polymerization [6] and polymer composites formation [7]. Dissolution of scCO 2 into polymers leads to a decrease in their viscosity, melting point (T m ), crystallization temperature (T c ) and glass transition temperature (T g ) [3,8,9], which is beneficial to polymer processing operations, especially for polymers that are sensitive to temperature degradation, such as poly(lactic acid) (PLA).…”

Section: Introductionmentioning

confidence: 99%

Rheological properties of HDPE and LDPE at the low-frequency range under supercritical CO2

Wan

Sun

Liu

et al. 2017

The Journal of Supercritical Fluids

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The effects of temperature, pressure (using helium as the pressurizing medium) and dissolved CO 2 concentration on the rheological properties of linear high-density polyethylene (HDPE) and branched-chain low-density polyethylene (LDPE) were carefully investigated using a high-pressure rheometer. The results showed that at low pressure, the rheology of the PEs was sensitive to pressure increase. As the pressure increased to higher values, the rheology leveled off for HDPE and increased for LDPE. Under supercritical CO 2 , the plasticization of the dissolved gas contributed primarily to the thickening effect of pressure. Furthermore, the loss factors decreased with increasing pressure and increased with increasing CO 2 pressure. Lastly, the effect of gas concentration was described by the Fujita-Kishimoto model on the assumption that the coupled effect of pressure and CO 2 concentration could be separated.

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Section: Introductionmentioning

confidence: 99%

Rheological properties of HDPE and LDPE at the low-frequency range under supercritical CO2

Wan

Sun

Liu

et al. 2017

The Journal of Supercritical Fluids

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“…Moreover, the physical absorption of CO 2 was related to the nature of the comonomer, and not with the level of incorporation in the main chains of glycidyl methacrylate alone. Many research teams have reported that the polymer itself physically interacted with the gas; reports of the solubilizing of supercritical CO 2 by polymers have suggested that the solubility of CO 2 was driven by the free volume of polymers 24,25 . This behavior can change the nature of the coating, assuming that n-butyl acrylate (Monomer 2) based polymers have a higher free volume compared with methyl acrylate based polymers; free volume being related to the temperature of the glass transition (T g ).…”

Section: Resultsmentioning

confidence: 99%

Novel polymer coating for chemically absorbing CO2 for safe Li-ion battery

Daigle

Asakawa

Péréa

et al. 2020

Sci Rep

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Gas evolution in Li-ion batteries remains a barrier for the implementation of high voltage materials in a pouch cell format; the inflation of the pouch cell is a safety issue that can cause battery failure. In particular, for manganese-based materials employed for fabricating cathodes, the dissolution of Mn 2+ in the electrolyte can accelerate cell degradation, and subsequently gas evolution, of which carbon dioxide (co 2) is a major component. We report on the utilization of a mixture of polymers that can chemically absorb the co 2 , including the coating of aluminum foils, which serve as trapping sheets, introduced into two Ah pouch cells-based on a LiMnfepo 4 (cathode) and a Li 4 ti 5 o 12 (anode). The pouch cells with trapping sheets experienced only an 8.0 vol% inflation (2.7 mmol CO 2 per gram of polymers) as opposed to the 40 vol% inflation for the reference sample. Moreover, the cells were cycled for 570 cycles at 1 C and 45 °C before reaching 80% of their retention capacity. The continuous quest for an inexpensive, high-energy battery for electrical vehicles (EVs) and energy storage (ES) applications has pushed industrial scientists to develop cells with high energy density by weight and volume. Optimizing the capacity of active materials in electrodes, and stacking increasingly more electrodes into a large format cell has become a valid path to increasing the energy density in battery packs, and minimizing their cost 1-4. On the other hand, safety should not be compromised, which is a real concern for consumers as no one wants to travel on potential "rolling bombs. " The implementation of a cathode with a high capacity and voltage to increase the battery's energy density is in vogue; consequently, manganese (Mn) or cobalt-based (Co) cathode materials have become prevalent in the production of high energy batteries. However, since the cost of Mn is lower than that of Co, reducing Co in cathode materials is a common approach to reduce cell costs 5. However, increasing the Mn content in active materials can cause other problems. The unwanted dissolution of Mn 2+ in the electrolyte (also initiated by water and HF) during cell operations can cause myriad side effects such as deposits on the anode surface and a reaction with the electrolyte where the liquid electrolyte may degrade rapidly during the first few cycles to produce gas. Gas evolution during cycling is one of the major problems associated with (especially) Mn-based cathodes. These gases principally constitute CO 2 , which originates from the decomposition of the liquid electrolyte in the presence of Mn ions 6-8. In the case of LMO, reaction occurs on the surface with Li + and Mn 2+ , and they are leached from the surface, therefore there is more Li ions migrate from the core, consequently electrons hopping from Mn 3+ to Mn 4+. The disproportionate reaction of Mn 3+ generates Mn 2+ /Mn 4+ which diffuses in electrolytes; studies with LMFP are limited. The degradation of the solvents in the presence of a Li 4 Ti 5 O 12 (LTO) anode and initiated by PF ...

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“…Free volume plays an important role in polymeric foaming. Free volume-rich polymers mix more favorably with CO2 [22]. A high fraction of free volume decreases melt viscosity [23], which is not good for bubble stability in the post-nucleation stage; it becomes easy for the CO2 molecules to escape from the bubbles.…”

Section: Resultsmentioning

confidence: 99%

Bubble Growth in Poly(methyl methacrylate) and Carbon Dioxide Mixture

Jie

2019

Polymers

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In this paper, we study bubble nucleation and growth in a poly(methyl methacrylate) and CO 2 mixture by molecular dynamics simulations. It is known in the foaming industry that the bubble size has a more uniform distribution with a higher start-up pressure. The real physical reason remains unclear. In this work, we found that the free volume-rich polymer segments could adsorb many small-size bubbles in the region close to the polymer chain. The existence of these small bubbles limits the number of free CO 2 molecules, which is helpful for bubble stabilization. Moreover, the free volume of polymer segments decreases with an increase of the start-up pressure. As a result, the size of the large bubbles becomes more uniform with a higher startup pressure.

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Polymer Miscibility in Supercritical Carbon Dioxide: Free Volume as a Driving Force

Cited by 15 publications

References 46 publications

Rheological properties of HDPE and LDPE at the low-frequency range under supercritical CO2

Rheological properties of HDPE and LDPE at the low-frequency range under supercritical CO2

Novel polymer coating for chemically absorbing CO2 for safe Li-ion battery

Bubble Growth in Poly(methyl methacrylate) and Carbon Dioxide Mixture

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