Polymer Carbon from pitch

The major use for graphite nowadays is for carbon fibers (to reinforce composites) produced either from pitch or from polymers such as polyacrylonitrile. Graphitization of these materials is performed stepwise by oxidation at 250° for losing much of the hydrogen, followed by carbonization in the absence of oxygen at 800°, and then by graphitization at 1400°-2500°. 

Adelhehn P, Hu Y-S, Chuenchom L, Antonietti M, Smarsly BM, Maier J (2007) Generation of hierarchical meso- and macroporous carbon from mesophase pitch by spinodal decomposition using polymer templates. Adv Mater 19 4012-4017... 

Sulphur has also been used extensively [101-105] as an additive and the yield of carbon from acenaphthylene can be increased. The use of too much sulphur resulted in a non-graphitizing carbon, but for a lesser amount, the reverse was true [101]. Greinke and Lewis [104] showed that sulphur incorporated in a strained ring system could be readily eliminated in the early stages of carbonization, but when incorporated in aromatic hydrocarbons, the sulphur containing polymer was stable up to high temperatures (1500°C) [99]. Rand [106] considered sulphur to be undesirable in pitch precursors used for making carbon fiber. 

Barr JB, Chwastiak S, Didchenko R, Lewis IC, Singer LS, High modulus carbon fibers from pitch precursor, Appl Polym Symp, Wiley, New York, 29, 161, 1976. 

Singer, "High Modulus Carbon Fibers from Pitch Precursor," J. Appl. Polym. 

Polymer pyrolysis refers to the pyrolytic decomposition of metal-organic polymeric compounds to produce ceramics. The polymers used in this way are commonly referred to as preceramic polymers in that they form the precursors to ceramics. Unlike conventional organic polymers (e.g., polyethylene), which contain a chain of carbon atoms, the chain backbone in preceramic polymers contains elements other than carbon (e.g., Si, B, and N ) or in addition to carbon. The pyrolysis of the polymer produces a ceramic containing some of the elements present in the chain. Polymer pyrolysis is an extension of the well-known route for the production of carbon materials (e.g., fibers from pitch or polyacrylonitrile) by the pyrolysis of carbon-based polymers (54). It is also related to the solution sol-gel process described in the previous section where a metal-organic polymeric gel is synthesized and converted to an oxide. 

Carbon fibers derived from polyacrylonitrile present low heat characteristics, so these type of composites are suited for applications where this aspect is mandatory. The investigation of polymers reinforced with pitch-based carbon fibers, vapor grown carbon fibers, carbon foam, and CNTs having high thermal conductivities opens up significant new markets based on multiple potential applications. 

Elongational behavior is induced in the entrance of the spinning hole and in the transition region from backhole to actual capillary. In practice hardly any permanent orientation is built up in this way, however, because molecular relaxation is rapid. Spinning hole profiles are smoothened only to prevent the formation of vortices which would lead to extrudate distortion. Promoting orientation already in the spinning holes is not common for melt spinning. It could be beneficial for the orientation of melt-spun liquid-crystalline polymers, however, for example in the production of carbon fiber from pitch. 

Yazami et al. [128, 129] studied the mechanism of electrolyte reduction on the carbon electrode in polymer electrolytes. Carbonaceous materials, such as cokes from coal pitch and spherical mesophase and synthetic and natural graphites, were used. The change in with composi-... 

The important bacterial storage material poly-hydroxybutyric acid is related metabolically and structurally to the lipids. This highly reduced polymer is made up of D-(3-hydroxybutyric acid units in ester linkage, about 1500 residues being present per chain. The structure is that of a compact right-handed coil with a twofold screw axis and a pitch of 0.60 nm.a Within bacteria it often occurs in thin lamellae 5.0 nm thick. Since a chain of 1500 residues stretches to 440 nm, there must be 88 folds in a single chain. Present in both cytoplasmic granules and in membranes,b polyhydroxybutyrate can account for as much as 50% of the total carbon of some bacterial In E. coli and many other bacteria polyhydroxybutyrate is present in a lower molecular mass form bound to calcium polyphosphates, proteins, or other macromolecules.d e It has also been extracted from bovine serum albumin and may be ubiquitous in both eukaryotes and prokaryotes.d/e The polymer may function in formation of Ca2+ channels in membranes.b/d... 

Carbon fibers are the most rigid and strongest of commonly used reinforcements. They are produced by the pyrolysis (high-temperature decomposition) of natural and synthetic materials, such as rayon, polyacrylonitrile (PAN), and pitch (the tacky residue left from the distillation of petroleum or coal tar). Carbon fibers are commercially available in a variety of formats, including single strands and bundles (known as tows). They are midway in density between glass and polymer fibers and are the most expensive of commonly used reinforcements. 

Activated carbons are obtained by physical (steam or C02 at 800°C-1000°C) or chemical (KOH at 700°C-800°C) treatment of carbons. The most usual carbon precursors are lignocellulosic derivatives, polymers, pitch, etc. Activated carbons are generally highly microporous (<2nm) with some amount of mesopores (2-50 nm) depending on the degree of activation, their BET SSA ranges from 1000 to 3500m2 g 1. 

Carbon molecular sieves, or carbogoric sieves are amorphous materials made by pyrolyz-ing coal, coconut shells, pitch, phenol-formaldehyde resin, or other polymers. EKslocations of aromatic microdomains in a glassy matrix give their porosity. Pores are slit-shaped. Pore structure is controlled by the temperature of the pyrolysis. Pore widths range from 3 A to 10 A. Acarbogenic sieve made from polyfurfuryl alcohol and combined with silica-alumina was selective for monomethylamine production from methanol and ammonia [54]. 

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