Polyacrylonitrile oxidation

Other polymer-analogous precursors employed include polyacrylonitrile (oxidative or nonoxidative cyclization [3-5]), poly( 1,2-butadiene) or poly(3,4-isoprene) [6,7], and polyalkinylacetylenes [8-11] prepared by the polymerization of butadiynes. The unsaturated side... 

Fig. 4.25 Adsorption isotherms showing low-pressure hysteresis, (a) Carbon tetrachloride at 20°C on unactivated polyacrylonitrile carbon Curves A and B are the desorption branches of the isotherms of the sample after heat treatment at 900°C and 2700°C respectively Curve C is the common adsorption branch (b) water at 22°C on stannic oxide gel heated to SOO C (c) krypton at 77-4 K on exfoliated graphite (d) ethyl chloride at 6°C on porous glass. (Redrawn from the diagrams in the original papers, with omission of experimental points.)...

Process. Any standard precursor material can be used, but the preferred material is wet spun Courtaulds special acrylic fiber (SAF), oxidized by RK Carbon Fibers Co. to form 6K Panox B oxidized polyacrylonitrile (PAN) fiber (OPF). This OPF is treated ia a nitrogen atmosphere at 450—750°C, preferably 525—595°C, to give fibers having between 69—70% C, 19% N density less than 2.5 g/mL and a specific resistivity under 10 ° ohm-cm. If crimp is desired, the fibers are first knit iato a sock before heat treating and then de-knit. Controlled carbonization of precursor filaments results ia a linear Dow fiber (LDF), whereas controlled carbonization of knit precursor fibers results ia a curly carbonaceous fiber (EDF). At higher carbonizing temperatures of 1000—1400°C the fibers become electrically conductive (22). 

This combination of monomers is unique in that the two are very different chemically, and in thek character in a polymer. Polybutadiene homopolymer has a low glass-transition temperature, remaining mbbery as low as —85° C, and is a very nonpolar substance with Htde resistance to hydrocarbon fluids such as oil or gasoline. Polyacrylonitrile, on the other hand, has a glass temperature of about 110°C, and is very polar and resistant to hydrocarbon fluids (see Acrylonitrile polymers). As a result, copolymerization of the two monomers at different ratios provides a wide choice of combinations of properties. In addition to providing the mbbery nature to the copolymer, butadiene also provides residual unsaturation, both in the main chain in the case of 1,4, or in a side chain in the case of 1,2 polymerization. This residual unsaturation is useful as a cure site for vulcanization by sulfur or by peroxides, but is also a weak point for chemical attack, such as oxidation, especially at elevated temperatures. As a result, all commercial NBR products contain small amounts ( 0.5-2.5%) of antioxidant to protect the polymer during its manufacture, storage, and use. 

Because the polymer degrades before melting, polyacrylonitrile is commonly formed into fibers via a wet spinning process. The precursor is actually a copolymer of acrylonitrile and other monomer(s) which are added to control the oxidation rate and lower the glass transition temperature of the material. Common copolymers include vinyl acetate, methyl acrylate, methyl methacrylate, acrylic acid, itaconic acid, and methacrylic acid [1,2]. 

Figure 1. Temperature variation of the conductivity for a cross-section of polymer electrolytes. PESc, poly (ethylene succinate) PEO, polyethylene oxide) PPO, polypropylene oxide) PEI, poly(ethyleneimine) MEEP, poly(methoxyethoxy-ethoxyphosphazene) aPEO, amorphous methoxy-linked PEO PAN, polyacrylonitrile PC, propylene carbonate EC, ethylene carbonate.

Polydithiazoles Polyoxadiazoles Polyamidines Pyrolyzed polyacrylonitrile Polyvinyl isocyanate ladder polymer Polyamide-imide Polysulfone Decompose at 525°C (977°F) soluble in concentrated sulfuric acid. Decompose at 450-500°C (842-932°F) can be made into fiber or film. Stable to oxidation up to 500°C (932°F) can make flexible elastomer. Stable above 900°C (1625°F) fiber resists abrasion with low tenacity. Soluble polymer that decomposes at 385°C (725°F) prepolymer melts above 405° C (76l.°F). Service temperatures up to 288° C (550°F) amenable to fabrication. Thermoplastic use temperature —102°C (—152°F) to greater than 150° C (302°F) acid and base resistant. 

Polyacetal Polyacrylamide Polyacrylonitrile Polycarbonate Polyethylene Polyethylene oxide Polyethylene terephthalate Poly isobutyl methacrylate Poly methacrylic acid Polymethyl methacrylate Polymonochlorotrifluoro ethylene Polypropylene Polystyrene... 

Oxide-water interfaces, in silica polymer-metal ion solutions, 22 460—461 Oxidimetric method, 25 145 Oxidization devices, 10 77-96 catalytic oxidization, 10 78—96 thermal oxidation, 20 77-78 Oxidized mercury, 23 181 Oxidized polyacrylonitrile fiber (OPF), 23 384... 

The use of pyrolyzed polyacrylonitrile (PPAN) and polyaniline (PAni) (Fig. 15.8(d), (e)) as catalysts for the ODH of ethylbenzene should only be mentioned here for the sake of completeness. Although first results were quite promising [45], this concept has so far not been followed in terms of N-doped nanocarbon catalyst development. This is most likely due to the poor self-oxidation resistance as a result of polar C-N bonds. 

In principle, molecular sieve carbons (MSC) can be achieved by the pyrolysis of thermosetting polymers such as polyvinylidene chloride, polyfurfuryl alcohol, cellulose, cellulose triacetate, polyacrylonitrile and phenol formaldehyde (Koresh 1980). An example is given by Trimm and Cooper (1970,1973) for the preparation of MSC (mixed with metallic compounds) for catalyst systems. A mixture of furfuryl alcohol, platinum oxide and formaldehyde was heated to 40°C and additional formaldehyde was added to ensure the... 

A completely different approach was taken by Koresh and Soffer (1980, 1986, 1987). Their preparation procedure involves a polymeric system like polyacrylonitrile (PAN) in a certain configuration (e.g. hollow fiber). The system is then pyrolyzed in an inert atmosphere and a dense membrane is obtained. An oxidation treatment is then necessary to create an open pore structure. Depending on the oxidation treatment typical molecules can be adsorbed and transported through the system. 

Polyacrylonitrile Poly(ethylene oxide) Poly(ethylene terephthalate) Polyisobutylene Poly(methyl methacrylate) Polypropylene Polystyrene... 

Asatekin A, Kang S, Elimelech M et al (2007) Anti-fouling ultrafiltration membranes containing polyacrylonitrile-graft-poly(ethylene oxide) comb copolymer additives. J Membr Sci 298 136-146... 

Martin and coworkers tried to prepare carbon tubes from the carbonization of polyacrylonitrile (PAN) in the channels of anodic oxide film (10). A commercially available film with a pore diameter of 260 nm was immersed in an aqueous acrylonitrile solution. After adding initiators, the polymerization was carried out at acidic conditions under N2 flow at 40°C. The PAN formed during the reaction was deposited both on the pore walls and on both sides of the film. Then the Film was taken from the polymerization bath, followed by polishing both faces of the film to remove the PAN deposited on the faces. The resultant PAN/alumina composite film was heat-treated at 250°C in air, and then it was heat-treated at 600°C under Ar flow for 30 min to carbonize the PAN. Finally, this sample was repeatedly rinsed in I M NaOH solution for the dissolution of the alumina film. The SEM observation of this sample indicated the formation of carbon tubes with about 50 xm long, which corresponds to the thickness of the template film. The inner structure of these tubes was not clear because TEM observation was not done. The authors claim that it is possible to control the wall thickness of the tubes with varying the polymerization period. 

Polyaniline has been formed in the pores of Cu- or Fe-exchanged MCM-41 by adsorption of aniline vapour and subsequent oxidative polymerization (Figure 7.23), and these molecular wires demonstrate significant electronic conduction, although less than that of bulk polyaniline. Pyrolysis of polyacrylonitrile in the pores produces a graphitelike carbon chain, which exhibits microwave conductivity ten times that of bulk carbonized polyacrylonitrile. Such materials have potential for use in information processing as storage capacitors. 

Two different polyacrylonitrile precursor carbon fibers, an A fiber of low tensile modulus and an HM fiber of intermediate tensile modulus were characterized both as to their surface chemical and morphological composition as well as to their behavior in an epoxy matrix under interfacial shear loading conditions. The fiber surfaces were in two conditions. Untreated fibers were used as they were obtained from the reactors and surface treated fibers had a surface oxidative treatment applied to them. Quantitative differences in surface chemistry as well as interfacial shear strength were measur-ed. 

Silica-supported cyclized polyacrylonitrile (PAN) metal complexes, claimed to be better oxidation catalysts than the polyphthalocyanine-metal complexes, have been obtained shown below as [11] ... 

Oxidation of the saturated heterocycle to sulfoxide and sulfone derivatives affords solvents for the preparation of polyacrylonitrile (62BEP613056), or corrosion inhibitors (e.g. 147)... 

Eq. (5) in conjunction with Eqs. (8) and (9) have, so far, provided adequate representation of experimental isotherms6 32, which are characterized by an initial con vex-upward portion but tend to become linear at high pressures. Values of K, K2 and s0 have been deduced by appropriate curve-fitting procedures for a wide variety of polymer-gas systems. Among the polymers involved in recent studies of this kind, one may cite polyethylene terephthalate (PET) l2 I4), polycarbonate (PC) 19 22,27), a polyimide l6,17), polymethyl and polyethyl methacrylates (PMMA and PEMA)l8), polyacrylonitrile (PAN)15), a copolyester 26), a polysulphone 23), polyphenylene oxide (PPO)25), polystyrene (PS) 27 28), polyvinyl acetate 29) and chloride 32) (PVAc and PVC), ethyl cellulose 24) (EC) and cellulose acetate (CA) 30,3I>. A considerable number of gases have been used as penetrants, notably He, Ar, N2, C02, S02 and light hydrocarbons. 

Similar systems were reported by Salvadori [50] and Lohray [51], who prepared different polyacrylonitrile- and polystyrene-supported 9-O-acylquinine derivatives. However, application of these systems afforded products with significantly lower enantiomeric excesses. In the case of Lohray s ligands, reuse of the polymeric ligands led to a decrease in enantioselectivity, and addition of osmium salt was necessary to maintain the catalytic activity. Despite Lohray s original report [51], one of his polymeric ligands was found by Song to be excellent for the oxidation of tnmv-stilbene with K3[Fe(CN6)] as secondary oxidant [52], Later, these results were critically evaluated by Sherrington [53],... 

Odian et a1 (Refs 113,133 150) showed that the deflagration rates of many composite AP solid propints were affected by gamma doses of 5 x I07 R. Two poly sulfide-based proplnts (Thiokol TP-L-3014 and TP-L-3014a) showed rate decreases, polyurethane (Thiokol TP-6-3129), polyacrylate (Hercules HES-6420) and polyacrylonitrile (HES-6648) based proplnts showed increases, while hydrocarbon (Thiokol TP-H-3062) and cellulose acetate (Hercules HES-5808) proplnts showed no changes in deflagration rate. Since the composite propint formulations contain various additives besides the binder and oxidizer, an effort was made to determine the effect of radiation on the deflagration rates of binder and oxidizer separately and independent of additives... 

MC MDI MEKP MF MMA MPEG MPF NBR NDI NR OPET OPP OSA PA PAEK PAI PAN PB PBAN PBI PBN PBS PBT PC PCD PCT PCTFE PE PEC PEG PEI PEK PEN PES PET PF PFA PI PIBI PMDI PMMA PMP PO PP PPA PPC PPO PPS PPSU Methyl cellulose Methylene diphenylene diisocyanate Methyl ethyl ketone peroxide Melamine formaldehyde Methyl methacrylate Polyethylene glycol monomethyl ether Melamine-phenol-formaldehyde Nitrile butyl rubber Naphthalene diisocyanate Natural rubber Oriented polyethylene terephthalate Oriented polypropylene Olefin-modified styrene-acrylonitrile Polyamide Poly(aryl ether-ketone) Poly(amide-imide) Polyacrylonitrile Polybutylene Poly(butadiene-acrylonitrile) Polybenzimidazole Polybutylene naphthalate Poly(butadiene-styrene) Poly(butylene terephthalate) Polycarbonate Polycarbodiimide Poly(cyclohexylene-dimethylene terephthalate) Polychlorotrifluoroethylene Polyethylene Chlorinated polyethylene Poly(ethylene glycol) Poly(ether-imide) Poly(ether-ketone) Polyethylene naphthalate Polyether sulfone Polyethylene terephthalate Phenol-formaldehyde copolymer Perfluoroalkoxy resin Polyimide Poly(isobutylene), Butyl rubber Polymeric methylene diphenylene diisocyanate Poly(methyl methacrylate) Poly(methylpentene) Polyolefins Polypropylene Polyphthalamide Chlorinated polypropylene Poly(phenylene oxide) Poly(phenylene sulfide) Poly(phenylene sulfone)... 

Metallisation of fibres is not only a physical process determined by absorption capacity of the fibres for the metal and diffusion capacity of the metal in the fibre structure, but also depends on chemical parameters such as chemical structure of the fibres, presence of functional groups, reactivity of the fibre and the metal, oxidation state of the metal and the presence, necessity and reactivity of supporting chemicals (e.g. reducing agent). Therefore, it was necessary first to study metallisation at different types of fibres in order to investigate which structure is most useful for further research. In this respect, viscose, cotton, natural silk and polyacrylonitrile fibres were investigated because of their different structure and properties and their availability in the New Independent States of the former Soviet Union (Uzbekistan, Kazakhstan, Kyrgyzstan). 

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