Phenols absorptions

Piotrowski JK. 1971. Evaluation of exposure to phenol Absorption of phenol vapor in the lungs through the skin and excretion of phenol in urine. Br J Ind Med 28 172-178. 

Nylon or other membranes that absorb phenolics should not be used. Membranes can be tested for phenolic absorption by comparing absorbance after single and double filtration. 

The partial IR spectrum of acid Subfraction 1 shows IR absorption at 3460 cm because of the pyrrolic nitrogen N-H absorption of carba-zole-like compounds. Amide carbonyl absorption appears at 1685 cm" The partial IR spectrum of acid Subfraction 2 shows the same two IR bands and additional bands at 3585 cm and 1650 cm owing to phenols and a second amide type. The partial IR spectrum of acid Subfraction 3 shows phenol absorption at 3585 cm S pyrrolic nitrogen absorption at 3460 cm S and strong carbonyl absorption at 1695 cm and 1725 cm characteristic of carboxylic acid dimers and monomers. In addition, absorption of hydrogen-bonded carboxylic acid and phenolic hydroxyl groups can be seen in the region of 3500-2300 cm" ... 

The fluorescence spectra of HNA In different solvents are Illustrated In Fig. 4. In this case, too, the emission mirrors the absorption of the qulnold species. The emission Is, however, dependent on the excitation wavelength (53). Curve 4 in Fig. 4 shows the fluorescence spectrum of HNA upon excitation In the phenol absorption region. Excitation of the cls-gulnold form produces a fluorescence spectrum in the same spectral region but of different shape (53). 

Band 1, 3 OSyL (3242 cm.". ) Hydrogen bonded 0—H absorption of the phenolic group (Table II). 

Phenol. Phenol monomer is highly toxic and absorption by the skin can cause severe blistering. Large quantities can cause paralysis of the central nervous system and death. Ingestion of minor amounts may damage kidneys, Hver, and pancreas. Inhalation can cause headaches, dizziness, vomiting, and heart failure. The threshold limit value (TLV) for phenol is 5 ppm. The health and environmental risks of phenol and alkylated phenols, such as cresols and butylphenols, have been reviewed (66). 

The maximum recommended film thickness is 25 p.m. At greater thicknesses, volatiles from the curing reaction, mainly water and some formaldehyde and phenol, can cause defects. These coatings have excellent electrical insulation properties, ie, up to 20 V/p.m, because of low moisture absorption and low conductance. The coatings are hard with low flexibiUty, depending on curing conditions and film thickness. 

Different phenoHc resins are used for different types of wood for example, plywood adhesives contain alkaline-catalyzed Hquid resole resins. Extension with a filler reduces cost, minimizes absorption, and increases bond strength. These resins have an alkaline content of 5—7% and are low in free phenol and formaldehyde. Because many resins have a high water content and limited storage stabiHty, they are frequently made at or near the mill producing the plywood product. The plywood veneers are dried, coated with resin, stacked for pressing, and cured at 140—150°C. 

Mesitylene. One of the principal derivatives of mesitylene is the stericaHy hindered phenol of the stmcture shown in Eigure 4. Its trade name is Ethanox 330 and it is produced by Albemarle Corporation (formerly Ethyl Corporation) (31). Ethanox 330 is an important noncoloring antioxidant and thermal stabiHzer for plastics, adhesives, mbber, and waxes (qv) (32,33) (see Antioxidants). The oral toxicity of Antioxidant 330 is extremely low (oral LD q in rats >15 g/kg) since its large size, C H gO, effectively eliminates absorption from the gastrointestinal tract. 

Early Synthesis. Reported by Kolbe in 1859, the synthetic route for preparing the acid was by treating phenol with carbon dioxide in the presence of metallic sodium (6). During this early period, the only practical route for large quantities of sahcyhc acid was the saponification of methyl sahcylate obtained from the leaves of wintergreen or the bark of sweet bitch. The first suitable commercial synthetic process was introduced by Kolbe 15 years later in 1874 and is the route most commonly used in the 1990s. In this process, dry sodium phenate reacts with carbon dioxide under pressure at elevated (180—200°C) temperature (7). There were limitations, however not only was the reaction reversible, but the best possible yield of sahcyhc acid was 50%. An improvement by Schmitt was the control of temperature, and the separation of the reaction into two parts. At lower (120—140°C) temperatures and under pressures of 500—700 kPa (5—7 atm), the absorption of carbon dioxide forms the intermediate phenyl carbonate almost quantitatively (8,9). The sodium phenyl carbonate rearranges predominately to the ortho-isomer. sodium sahcylate (eq. 8). 

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

The exterior durabiHty of relatively stable coatings can be enhanced by use of additives. Ultraviolet absorbers reduce the absorption of uv by the resins and hence decrease the rate of photodegradation. Eurther improvements can be gained by also adding free-radical trap antioxidants (qv) such as hindered phenols and especially hindered amine light stabilizers (HALS). A discussion of various types of additives is available (113). 

The procedure of simultaneous extracting-spectrophotometric determination of nitrophenols in wastewater is proposed on the example of the analysis of mixtures of mono-, di-, and trinitrophenols. The procedure consists of extraction concentrating in an acid medium, and sequential back-extractions under various pH. Such procedures give possibility for isolation o-, m-, p-nitrophenols, a-, P-, y-dinitrophenols and trinitrophenol in separate groups. Simultaneous determination is carried out by summary light-absorption of nitrophenol-ions. The error of determination concentrations on maximum contaminant level in natural waters doesn t exceed 10%. The peculiarities of application of the sequential extractions under fixed pH were studied on the example of mixture of simplest phenols (phenol, o-, m-, />-cresols). The procedure of their determination is based on the extraction to carbon tetrachloride, subsequent back-extraction and spectrophotometric measurement of interaction products with diazo-p-nitroaniline. 

The very low water absorption of bis-phenol A polycarbonates contributes to a high order of dimensional stability. Table 20.6 shows how the water absorption of j in thick samples changes with time and environmental conditions and the consequent influence on dimensions. 

In a general comparison with phenolic resins, the U-F materials are cheaper, light in colour, are lacking in odour, have better resistance to electrical tracking but have an inferior heat resistance and a higher water absorption. 

---