Exposure carbonation

Oberdorster, G. (2002) Toxicokinetics and effects offibrous and nonfibrous particles. Inhalation Toxicology, 14 (1), 29—56. Warheit, D.B. (2006) What is currently known about the health risks related to carbon nanotube exposures Carbon,... 

Warheit, D.B., What is currently known about the health risks related to carbon nanotube exposures Carbon 44, 1064-1069, 2006. 

Adaptation to low levels, 1.5-3.0% carbon dioxide, has occurred with chronic exposure. Carbon dioxide at room temperature will not injure the skin, but frostbite may result from contact with dry ice or from the gas at low temperatures. 

Jones C.W. and Koros W.J., Carbon molecular sieve gas separation membranes—II. Regeneration following organic exposure. Carbon 52 1427 (1994). 

Sulfur Cements Sulfur base cements are heated in a kettle similar to asphalts and joints poured hot, done in several steps to assure the joints are filled before cement cools below flowable temperature. Sulfur cements are plasticized using 0.6% olefin polysulfide (Thiokol ). Other plasticizers have been tried but none have proven as effective as the polysulfide. Sulfur cements are filled with either silica or carbon depending on exposure (carbon in the case of hydrofluoric... 

In either of these above exposures, carbon brick is the material of choice. 

The analysis of rubbers containing large amounts of carbon black by IR spectroscopy is difficult, particularly studies of their chemical evolution upon ageing. The use of a horizontal ATR accessory equipped with a germanium crystal is described. Horizontal ATR(Ge)/FTIR analysis of both thermal- and photooxidations of EPDM, polychloroprene and NBR were first validated by conventional transmission spectroscopy in the absence of carbon black. Horizontal ATR(Ge) was then used with fully formulated rubbers with the aim of studying their long-term behaviour. The effects of temp., UV exposure, carbon black or stress as well as the oxidation profile across the materials on... 

TPE-E (polyester-based thermoplastic elastomers) are subject to UV-llght degradation in outdoor weathering and therefore have to be stabiiized for extended solar exposure. Carbon black provides the best protection. Without suitable stabilization, embrittiement as weii as gioss ioss occur under extended irradiation by UV iight [83]. 

Jones, C. W., and Koros, W. J. (1994b). Caron molecular sieve gas separation membranes—n. Regeneration following organic exposure. Carbon 32(8), 1427-1432. 

Alkanes from CH to C4gFlg2 typically appear in crude oil, and represent up to 20% of the oil by volume. The alkanes are largely chemically inert (hence the name paraffins, meaning little affinity), owing to the fact that the carbon bonds are fully saturated and therefore cannot be broken to form new bonds with other atoms. This probably explains why they remain unchanged over long periods of geological time, despite their exposure to elevated temperatures and pressures. 

Chloroform undergoes oxidation to the very poisonous phosgene upon exposure to light and air. Commercial specimens are therefore stored in brown bottles and contain 1-2 per cent, of alcohol the latter converts the toxic phosgene into the harmless substance diethyl carbonate ... 

Anthracene and maleic anhydride. In a 50 ml. round-bottomed flask fitted with a reflux condenser, place 2 0 g. of pure anthracene, I 1 g. of maleic anhydride (Section 111,93) and 25 ml. of dry xylene. Boil the mixture under reflux for 20 minutes with frequent shaking during the first 10 minutes. Allow to cool somewhat, add 0 5 g. of decolourising carbon and boil for a further 5 minutes. Filter the hot solution through a small, preheated Buchner funnel. Collect the solid which separates upon coohng by suction filtration, and dry it in a vacuum desiccator containing paraffin wax shavings (to absorb traces of xylene). The yield of adduct (colourless crystals), m.p. 262-263° (decomp.), is 2-2 g. Place the product (9 10-dihydroanthracene-9 10-cndo-ap-succinic anhydride) in a weU-stoppered tube, since exposure to air tends to cause hydration of the anhydride portion of the molecule. 

Prior to determination of an isotherm, all physisorbed material has to be removed from the surface of the adsorbent. This is best achieved by exposure of the surface to high vacuum, the exact conditions required (temperature and residual pressure) being dependent on the particular gas-solid system. In routine determinations of surface area it is generally advisable not to remove any chemisorbed species which may be present thus, the hydroxylated oxides are usually outgassed at 1S0°C. Microporous adsorbents such as zeolites or active carbons however require higher temperatures (350-400 C, say) for complete removal of physisorbed material from their narrowest pores. An outgassing period of 6-10 hours (e.g. overnight) is usually sufficient to reduce the residual pressure to 10 Torr. 

Furfural is very thermally stable in the absence of oxygen. At temperatures as high as 230°C, exposure for many hours is required to produce detectable changes in the physical properties of furfural, with the exception of color (17). However, accelerating rate calorimetric data shows that a temperature above 250°C, in a closed system, furfural will spontaneously and exothermically decompose to furan and carbon monoxide with a substantial increase in pressure. The pressure may increase to 5000 psi or more, sufficient to shatter the container (18). 

Three approaches have been identified that reduce susceptibility of CA resists to airborne contamination. In the first, process engineering changes such as the addition of special activated carbon filters to the environmental chambers surrounding the exposure tools (76,79), overcoating the resist with a soluble protective film to isolate the resist from the environment (77,80,81), or modifications of the process flow to minimize the time interval between exposure and post-exposure bake have been shown to improve CA resist processibibty. 

As a class of compounds, the two main toxicity concerns for nitriles are acute lethality and osteolathyrsm. A comprehensive review of the toxicity of nitriles, including detailed discussion of biochemical mechanisms of toxicity and stmcture-activity relationships, is available (12). Nitriles vary broadly in their abiUty to cause acute lethaUty and subde differences in stmcture can greatly affect toxic potency. The biochemical basis of their acute toxicity is related to their metaboHsm in the body. Following exposure and absorption, nitriles are metabolized by cytochrome p450 enzymes in the Hver. The metaboHsm involves initial hydrogen abstraction resulting in the formation of a carbon radical, followed by hydroxylation of the carbon radical. MetaboHsm at the carbon atom adjacent (alpha) to the cyano group would yield a cyanohydrin metaboHte, which decomposes readily in the body to produce cyanide. Hydroxylation at other carbon positions in the nitrile does not result in cyanide release. 

Activated carbons contain chemisorbed oxygen in varying amounts unless special cate is taken to eliminate it. Desired adsorption properties often depend upon the amount and type of chemisorbed oxygen species on the surface. Therefore, the adsorption properties of an activated carbon adsorbent depend on its prior temperature and oxygen-exposure history. In contrast, molecular sieve 2eohtes and other oxide adsorbents are not affected by oxidi2ing or reducing conditions. 

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