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PFASs in Consumer Products
Published in David M. Kempisty, LeeAnn Racz, Forever Chemicals, 2021
Simona Andreea Ba˘lan, Qingyu Meng
Fluoropolymers are large molecules with fluorinated carbon atoms as part of the polymeric backbone. They are very durable materials that cannot degrade to PFAAs under typical environmental conditions, but certain PFAAs have been used as processing aids in their manufacturing and can occur as impurities. Moreover, fluoropolymers may release PFCAs, including PFOA, during combustion at temperatures between 180 and 800 °C (Feng et al. 2015, Schlummer et al. 2015). Examples of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF). Some fluoropolymers, such as perfluoroalkoxy alkanes (PFAs) and fluoroelastomers, are made from a mix of perfluoroether monomers and tetrafluoroethylene (TFE) or hexafluoropropylene (HFP) (Nordic Council of Ministers et al. 2020). They are still classified as fluoropolymers rather than PFPEs because the ether linkages occur in the side chains, not in the polymer backbone.
Triboelectric Materials for Nanoenergy
Published in Sam Zhang, Materials for Energy, 2020
Xiude Yang, Jun Dong, Juanjuan Han, Qunliang Song
Based on our experience, we know that almost all materials in nature such as metal, polymer, silk, and wood have triboelectrification effect. Theoretically, all of them can be used to fabricate TENG, which indicates that a wide range of materials can be selected for TENG. In 1957, John Carl Wilcke proposed the first triboelectric series on static charge based on the difference in capacity of materials to gain electrons or lose electrons [9,10]. The triboelectric series of some common materials are given in the Figure 3.10. During triboelectrification process, the materials close to the top of figure tend to gain electrons and accumulate negative charges due to their large electron affinity, while the materials close to the bottom of figure tend to lose electrons and accumulate positive charges. Previous researches have shown that the farther apart two materials are in this table, the more transferred charges they generate in the friction process. Consequently, in order to obtain more triboelectric charges and thus larger output, we usually choose a pair of tribomaterials with a large difference in electronegativity (or electron affinity) as the functional layer of TENG (such as a metal and a polymer). Especially, polytetrafluoroethylene (PTFE), polydimethylsiloxane (PDMS), polyvinyl fluoride (PVC), and polyimide (Kapton), which are located at the bottom of the table, are often studied intensively as negative polarity materials owing to their good electronegativity.
Nanotechnology Impact on the Automotive Industry
Published in Kaufui V. Wong, Nanotechnology and Energy, 2017
Kaufui V. Wong, Patrick Andrew Paddon
The separators of batteries are also crucial to their efficiency by allowing maximum usable power within the battery and ensuring minimal energy loss on recharging. Both can be attained by lowering the air resistance property of the separators. Table 8.4 shows the material characteristics of various separators composed of micro- and nanofibers, and Table 8.5 shows their electrical properties. The nanofibers of the microporous polymeric battery separator are composed of at least one polymer of polyacrylonitrile, cellulose, polypropylene, polyethylene, polybutylene, polyamide, polyvinyl alcohol, polyethylene terephthalate, polybutylene terephthalate, polysulfone, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl pentene, polyphenylene sulfide, polyacetyl, polyurethane, aromatic polyamide, semi-aromatic polyamide, polypropylene terephthalate, polymethyl methacrylate, polystyrene, and blends, mixtures and copolymers thereof. CE2 stands for Celgard 2325 separator, which is used as a comparative example of prior technology.
Symmetric expressions of surface tension components
Published in The Journal of Adhesion, 2023
Reinosuke Kusano, Yukihiro Kusano
As reported in ref.[23], the surface tension of the saltwater tends to increase as the salt concentration increases, the trend agreeing with literature,[32–34] though only results at low concentrations are reported, except in ref.[23] The trend of increasing surface tension is due to the surface excess of saltwater.[23] The selection of these surfaces is well justified in Figure 8, as they have different enough slopes as demonstrated. This highlights another important aspect of estimating surface tension components of liquids. In other words, one must make an adequate selection of test solid surfaces. A large enough difference between the slopes of the solids must exist, and additionally the radii of the obtained circle must be small. Thus, sample data from ref.[35] regarding the different surface tension components of solids has been processed and plotted on Figure 9, relating the minimum radius with the slope . Here, solid materials selected are polyvinyl fluoride (PVF), polyimide (PI), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyethylene (PE).
Selection of optimal glazing material for solar thermal applications using grey relational analysis
Published in International Journal of Ambient Energy, 2021
M. Renuka, K. Balaji, D. Sakthivadivel, M. Meikandan, P. Ganesh Kumar
The weighted normalised matrix values for different glazing materials as shown in Table 3 to investigate the values using grey relational analysis approach. The grey relational grade and rank order of each glazing material is calculated using Equations (1–4). The value of the distinguishing coefficient ψ is taken as 0.5, as equal weighting is given to the responses. The distinguishing factor can be fixed between 0 and 1. The value 0.5 is fixed to avoid deviation of the results. The value can be assigned according to the priority given to a particular response, 0.5 means equal weight is given to all the responses under consideration. The ranking is arranged in the ascending order based on grey relational grade value such as Crystal glass> Low density polyethylene>Polytetrafluoroethylene>Polyamide>Polyethylene terephthalate> Polypropylene> High density polyethylene> Polycarbonate> Polysulfone> Polyvinylidene fluoride> Polyvinyl fluoride> PMMA / Acrylic as shown in Table 3.
FTIR spectrum of vinyl fluoride near 3.6 μm: rovibrational analysis of the ν4+ν7 band and modelling Coriolis resonances in a seven-level polyad
Published in Molecular Physics, 2018
P. Stoppa, A. De Lorenzi, A. Pietropolli Charmet, S. Giorgianni, N. Tasinato, A. Gambi
In past years, the interest in spectroscopic studies of halogenated ethenes has greatly increased partly due to their potential role as air pollutants. Many compounds are reactive substances and the most important atmospheric transformation processes involve photolysis and chemical reactions with ozone, hydroxyl and nitrate radicals [1–3]. In this context, vinyl fluoride (H2C=CHF) is a compound of a certain importance since it is subject to being accidentally released into the atmosphere when employed in industrial productions of synthetic resins such as polyvinyl fluoride and other fluorinated copolymers that are among the most versatile plastics. Besides, vinyl fluoride, like vinyl chloride and vinyl bromide, is mutagenic and clastogenic and potentially a carcinogenic agent for humans [4].