The modification of polypropylene structure by low-frequency glow discharge

Rishina, L. A.; Vizen, E.I.; Shibryaeva, L. S.; Sosnovskaya, L. N.; Veretennikova, A. A.; Lodygina, Tati Yana A.; Gilman, A. B.

doi:10.14314/polimery.1998.034

Cited by 2 publications

(1 citation statement)

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“…In addition, due to the oxidative nature of VO 2 + it is possible, that new hydroxyl or keto functionalities were created in the polymer chain via slow autoxidation. [65][66][67] However it can be considered that the oxidation of the polypropylene under the present conditions was rather negligible as indicated by the low intensity of both carbonyl features observed in the ATR-FTIR spectra of the pristine and aged polymer. Therefore, it can be concluded that mainly the graphite compound of the BPP was attacked by the highly oxidizing positive electrolyte.…”

Section: Resultsmentioning

confidence: 99%

Chemical Stability of Graphite-Polypropylene Bipolar Plates for the Vanadium Redox Flow Battery at Resting State

Satola

Kirchner

Komsiyska

et al. 2016

J. Electrochem. Soc.

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Current collectors called bipolar plates (BPP) are important elements within the conversion unit of the vanadium redox flow battery (VRFB). They are in direct contact with acidic electrolytes, containing vanadium species in different oxidation states. The influence of the state of charge (SOC) on the calendar aging of BPPs was examined. Graphite-polypropylene BPPs were immersed in positive and negative vanadium electrolytes at 0%, 20%, 80% and 100% SOC for 30, 90 and 190 days. H 2 gas evolution was observed as side reaction on the surface of the BPPs in the negative electrolyte. After electroless aging, scanning electron (SEM) and confocal microscopy measurements showed no significant changes in the surface morphology. The electrical conductivities of the BPPs were not affected significantly. However, contact angle (θ) measurements revealed that the positive electrolyte influenced the wettability of the BPPs. X-ray photoelectron (XP) spectroscopy showed progressing oxidation of the BPP surfaces in the positive electrolyte and adsorption or entrapment of vanadium ions in the pores at high SOC. Cyclic voltammograms (CV) provided evidence that the graphite was oxidized combined with an increase in effective surface area. ATR-FTIR measurements showed slight oxidation of pure polypropylene granulate in the positive electrolyte with 100% SOC. The increasing energy power supply from intermittent renewable energy sources requires a rapid introduction of efficient energy storages. One promising technology is the vanadium redox flow battery (VRFB), as it enables to scale the power and the storage capacity independently according to specific requirements.1,2 In addition the VRFB is characterized by a fast response time and long electrolyte cycle life.3 Each reaction unit in a VRFB stack is composed of two half-cells separated by a membrane consisting of an electrode in contact with a current collector called bipolar plate (BPP).2 In a battery stack the BPPs are "non-active" components that conduct current from one cell to the other. They physically separate adjacent cells from each other while staying in contact with acidic half-cell electrolytes containing vanadium species in different oxidation states on each side. 4 For brevity we call the V 2+ /V 3+ solution "negative electrolyte" and the VO 2+ /VO 2 + solution "positive electrolyte". While vanadium redox reactions mainly occur on the surfaces of the porous electrodes, they could also occur unintentionally on the surfaces of the BPPs. [5][6][7] Therefore, a good BPP should be characterized by a high chemical and mechanical stability, high electrical conductivity and impermeability to preclude leakage. 8 Metallic BPPs are usually not used in VRFB as they corrode in acidic environments and would need a protective layer.5,9,10 Therefore, graphite based BPPs are commonly used as they possess a good electrical conductivity and a better chemical stability. 4 However, pure graphite plates are not favored as BPPs due to their high weight and cost as well as low mechanical stre...

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Section: Resultsmentioning

confidence: 99%