Phenylene oxide benzimidazole

Larson et al. compared the performance of PA-doped m-PBI with bis-fiuorinated acid-doped phenylene oxide benzimidazole (PBIO) [85]. PBI was purchased from Celanese and PBIO was purchased from Eumatech. The polymers were dissolved in DMAc and NMP, respectively, after IR, elemental analysis, and NMR confirmed structure. The PBIO polymer solution was combined with solutions of bisfluorinated acids (disulfonate, Cl-bis-imide, or C4-bis-imide) or solutions of bisfluorinated acid and silica. The polymers were cast onto glass plates and solvent was removed to form a membrane, m-PBI membranes were doped with 85% phosphoric acid to a level of 600 mol... 

Whereas UL 94 delivers only a classification based on a pass-and-fail system, LOI can be used to rank and compare the flammability behavior of different materials. In Figure 15.2 the increasing LOI values are presented for different polymers as an example POM = poly(oxymethylene), PEO = poly(ethyl oxide), PMMA = poly(methyl methacrylate), PE = polyethylene), PP, ABS, PS, PET = polyethylene terephthalate), PVA = poly(vinyl alcohol), PBT, PA = poly(amide), PC, PPO = poly(phenylene oxide), PSU, PEEK = poly(ether ether ketone), PAEK = poly(aryl ether ketone), PES, PBI = poly(benzimidazole), PEI = poly(ether imide), PVC = poly(vinyl chloride), PBO = poly(aryl ether benzoxazole), PTFE. The higher the LOI, the better is the intrinsic flame retardancy. Apart from rigid PVC, nearly all commodity and technical polymers are flammable. Only a few high-performance polymers are self-extinguishing. Table 15.1 shows an example of how the LOI is used in the development of flame-retarded materials. The flame retardant red phosphorus (Pred) increases... 

PB PBI PBMA PBO PBT(H) PBTP PC PCHMA PCTFE PDAP PDMS PE PEHD PELD PEMD PEC PEEK PEG PEI PEK PEN PEO PES PET PF PI PIB PMA PMMA PMI PMP POB POM PP PPE PPP PPPE PPQ PPS PPSU PS PSU PTFE PTMT PU PUR Poly(n.butylene) Poly(benzimidazole) Poly(n.butyl methacrylate) Poly(benzoxazole) Poly(benzthiazole) Poly(butylene glycol terephthalate) Polycarbonate Poly(cyclohexyl methacrylate) Poly(chloro-trifluoro ethylene) Poly(diallyl phthalate) Poly(dimethyl siloxane) Polyethylene High density polyethylene Low density polyethylene Medium density polyethylene Chlorinated polyethylene Poly-ether-ether ketone poly(ethylene glycol) Poly-ether-imide Poly-ether ketone Poly(ethylene-2,6-naphthalene dicarboxylate) Poly(ethylene oxide) Poly-ether sulfone Poly(ethylene terephthalate) Phenol formaldehyde resin Polyimide Polyisobutylene Poly(methyl acrylate) Poly(methyl methacrylate) Poly(methacryl imide) Poly(methylpentene) Poly(hydroxy-benzoate) Polyoxymethylene = polyacetal = polyformaldehyde Polypropylene Poly (2,6-dimethyl-l,4-phenylene ether) = Poly(phenylene oxide) Polyp araphenylene Poly(2,6-diphenyl-l,4-phenylene ether) Poly(phenyl quinoxaline) Polyphenylene sulfide, polysulfide Polyphenylene sulfone Polystyrene Polysulfone Poly(tetrafluoroethylene) Poly(tetramethylene terephthalate) Polyurethane Polyurethane rubber... 

In comparison with the membranes with common aromatic skeletons such as poly-sulfane (PS), poly(ether ether ketone), poly(phthalazinon ether sulfone ketone), poly(etherimide), poly(benzimidazole), poly(phenylene oxide), polysiloxane, poly(oxyethylene) methacrylate, poly(arylene ether sulfone), and polyethersulfone Cardo, which are generally at high price and of complicated synthesis processes, the most important advantages of the aliphatic polymer materials as PEM membranes are their low cost, easy preparation, and simple structure. These aliphatic PEMs are particularly environmentally friendly (e.g., if the quatemization process is proceeded when these aromatic membranes are used for alkaline PEM fuel cells, the synthesis route uses chloromethyl ether for chloromethylation, which is very toxic and carcinogenic). However, the stability of the aliphatic PEMs is not very good. This is probably the biggest challenge when they are used in electrochemical devices. 

Poly[2,2 -(m-phenylene-5,5 -benzimidazole)] (PBI) is a very high glass transition temperature (Tg 430°C), commercially available material. It possesses excellent mechanical properties, but is difficult to process into large parts and has high moisture regain and poor thermo-oxidative stability at temperatures above approximately 260 °C. Polyimides, especially the thermoplastic polyimides, offer attractive thermo-oxidative stability and processibility, but often lack the thermal and mechanical characteristics necessary to perform in applications such as the matrix for high use-temperature (over 300 °C) structural composites (for example, carbon fiber reinforced) for aerospace use. The attempt to mitigate... 

Literature reveals that in the oxidative cyclization of aldeltyde and o-phenylene-diamine, the formation of the required 2-aiyl-l/f-benzimidazole is accompanied by the occurrence of 1-benzylated 2-aryl-1/f-benzimidazoles as side products [46], and sometimes these disubstituted derivatives have been isolated as the main product [47, 48]. The present protocol gives 2-aryl-1/7-benzimidazole selectively. Further, we extended our studies on oxidative reactions of aldehydes with o-aminothiophe-nol. Although thiols are good nucleophiles and SET agents [49], in present studies, no substitution of the halogen atom or the nitro group, dealkylation/debenzoy lation, took place as reported earlier [50-52]. Fmiher, the dithioacetal formation is a common reaction of aldehydes with thiols [53] no competitive dithioacetal formation was observed imder the present conditions. Doping of Mn promotes the activity and... 

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