Styrene

Objective: Given the paucity of studies that have examined variability in biological measures of exposure to workplace contaminants, we quantified the intra- and inter-individual sources of variation in urinary levels of mandelic acid (MA) and phenylglyoxylic acid (PGA) among workers exposed to styrene. A secondary objective was to examine effects of job task and the timing of sampling during the workweek on the variation in workers' urinary styrene metabolite levels. Methods: As part of routine biological monitoring, a total of 1,714 measurements of MA and PGA collected from 331 workers between 1985 and 1999 from eight reinforced-plastics plants were abstracted from laboratory reports. To evaluate sources of variation in levels of urinary styrene metabolites, we applied random-effects models. The influence of job task and day of sampling on metabolite levels was examined using mixed-effects models. Results: PGA levels were characterized by less variation than levels of MA, as were metabolite levels expressed in terms of urinary creatinine concentration. The relative magnitude of the inter-individual to the intra-individual source of variation was generally higher for post-shift urine samples than for pre-shift urine samples. As expected, urinary metabolite levels were highest for laminators and for samples collected at the latter end of the workweek. Owing to the effects of variation from day-to-day, estimates of workers' exposures that rely on single measurements would generally perform poorly in a regression analysis designed to examine effects resulting from chronic exposure. However, the bias in an observed slope coefficient would be diminished if a second or third urine sample were collected. Conclusions: Quantification of the intra- and inter-individual sources of variation provides useful information that can be used to design optimal sampling strategies, which would allow for the collection of sufficient data to estimate workers' exposures reliably when evaluating health risks associated with occupational contaminants.

Styrene who is also known as ethylbenzene,vinybenzene and phenylethene is an organic compound with the chemical formula C 6 H 5 CH=CH 2. Although styrene was discovered way back in 1839, its commercial production and applications were developed in the 1930s. Post world war period witnessed a boom in styrene demand due to its application in the manufacture of synthetic rubber. This led to a dramatic increase in styrene capacity. Styrene has wide application in producing plastic and synthetic rubber industry. It is mostly used in manufacturing of polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), styrene-butadiene rubber (SBR) and lattices, unsaturated polyester resins (UP resins) and miscellaneous uses like textile auxiliaries, pigment binders polyester resin, aromatics and intermediate industries. Worldwide, there are commonly five methods of manufacturing of styrene such as catalytic dehydrogenation of ethylbenzene, Oxidation of ethylbenzene to ethyl hyroperoxide , side-chain chlorination of ethlybenzene followed by dechlorination, side-chain of chlorination of ethylbenzne hydrolysis to the corresponding alcohols followed by dehydration and pyrolysis of petroleum recovery. In an effort to find a sustainable method of manufacturing of styrene from ethylbenzene, several design objectives were chosen as a necessity for the proposed system such as identifying suitable catalyst, the economic factor, environmental factor, strategic location to build for styrene plant, the design specifications on the reactors and distillation column used in the plant, the market price and also not to forget the safety issue relating to the plant. Obtaining this data was very crucial before scaling up the design of a complete industrial plant. For the final design of our project, we includes the process flow diagram (PFD) and also Piping and Instrumentation Diagram (P&ID) created by Microsoft Visio, finalized site selection to build the styrene plant, the analysis of reactor and distillation design plus with HAZOP study and FTA analysis in concerning safety relating issue toward the each equipment used in the process background of producing styrene. From this variable aspect, we conclude the proposed plant design would indeed be economically viable and profit inducing.

A number of volatile organic compounds (VOCs) including acetone, methyl ethyl ketone, toluene, ethylbenzene, m,p-xylene, styrene, and o- xylene released during food decaying processes were measured from three types of decaying food samples (Kimchi (KC), fresh fish (FF), and salted fish (SF)). To begin with, all the food samples were contained in a 100-mL throwaway syringe. These samples were then analyzed sequentially for up to a 14-day period. The patterns of VOC release contrasted sharply between two types of fish (FF and SF) and KC samples. A comparison of data in terms of total VOC showed that the mean values for the two fish types were in the similar magnitude with 280 ± 579 (FF) and 504 ± 1,089 ppmC (SF), while that for KC was much lower with 16.4 ± 7.6 ppmC. There were strong variations in VOC emission patterns during the food decaying processes between fishes and KC that are characterized most sensitively by such component as styrene. The overall results of this study indicate that concentration levels of the VOCs differed significantly between the food types and with the extent of decaying levels through time.

The association of occupational exposure to 1,3-butadiene and chromosomal damage in peripheral blood lymphocytes was studied in 40 workers from two production facilities. Control persons, 30 in all, were chosen from other departments of the same plants, and they were roughly matched for age and smoking habits. The exposure levels to ambient butadiene were measured both by personal sampling using diffuse monitors and by stationary sampling at production and handling sites. Chromosome aberrations (CA), micronuclei (MN) and sister-chromatid exchanges (SCE) in peripheral lymphocytes were analyzed as markers of exposure. Smoking had a slight effect on the frequency of MN, and the mean frequency of SCEs was also higher in smokers than in non-smokers. No effect of smoking, however, was seen in relation to chromosomal aberrations. No exposure related effects were seen in any of the three cytogenetic endpoints in either of the butadiene production plants, representing typical low (below 3 pp...

Herein, we report the synthesis of monomethacryloyl sucrose esters, and their successful free radical homo- and co-polymerisation with styrene, methylmethacrylate, α-and β-pinene. The chemical, physical, structural and surface chemical properties of these polymers, containing a hydrophobic olefin backbone and hydrophilic sugar moieties as side chains, have been investigated. Biodegradation tests of the copolymer samples by a microbial fungal culture (Aspergillus niger) method showed good biodegradability. The chemical structure and surface chemistry of the synthesized homo- and co-polymers demonstrate their potential technological relevance as amphiphilic and biodegradable polymers.

Metal nanoparticles with different shapes have different crystallographic faces. It is therefore of interest to study the effect of the shape of metal nanoparticles on their catalytic activity in various organic and inorganic reactions. Truncated triangular silver nanoplates with well-defined planes were synthesized by a simple solvothermal approach. The activity of these truncated triangular silver nanoparticles was compared with that of cubic and near-spherical silver nanoparticles in the oxidation of styrene in colloidal solution. It was found that the crystal faces of silver nanoparticles play an essential role in determining the catalytic oxidation properties. The silver nanocubes had the {100} crystal faces as the basal plane, whereas truncated triangular nanoplates and near-spherical nanoparticles predominantly exposed the most-stable {111} crystal faces. As a result, the rate of the reaction over the nanocubes was more than 14 times higher than that on nanoplates and four times higher than that on near-spherical nanoparticles.

Antimicrobial releasing biomaterial coatings have found application for instance in the fixation of orthopedic joint prostheses and central venous catheters. Most frequently, the release kinetics is such that antimicrobially-effective concentrations are only reached within the first days to weeks after implantation, leaving no local antimicrobial release available when a biomaterial-associated infection occurs later. Here we compare the ad libitum release of chlorhexidine and silver-sulfadiazine from a central venous catheter with their release from a new, on-demand release coating consisting of a temperature-sensitive copolymer of styrene and n-butyl (meth)acrylate. The copolymer can be loaded with an antimicrobial, which is released when the temperature is raised above its glass transition temperature. Ad libitum release of chlorhexidine and silver-sulfadiazine from a commercially-purchased catheter and associated antimicrobial efficacy against Staphylococcus aureus was limited to...

Based on the studies performed a sensitive and simple method for the determination of benzene and styrene metabolites in urine has been developed. The developed procedure can be used for biological monitoring of occupational and environmental exposure. Urine samples for the determination of styrene metabolites (phenylglyoxylic acid--PGA and mandelic acid--MA) were only acidified with formic acid, while those for the determination of benzene metabolite (S-phenyl-mercapturic acid--S-PMA) were additionally extracted with ethyl acetate. The measurement was performed by high performance liquid chromatography--tandem mass spectrometry (HPLC-MS/MS). The quality of our analysis was verified using internal and external quality control. Limit of detection for S-PMA was 0.33 microg/l, for MA--60 microg/l and for PGA--40 microg/l; precision was 2-3% and recovery 94-98%. The method for the quantification of benzene and styrene metabolites can be used for biological monitoring of occupational and...

Chiral molecular recognition is a pivotal phenomenon in biomolecular science, governed by subtle balances of intermolecular forces that are difficult to quantify. Non-covalent interactions involving aromatic moieties are particularly important in this realm, as recurring motifs in biomolecular aggregation. In this work, we use high-resolution broadband rotational spectroscopy to probe the dynamic conformational landscape enclosing the self-pairing topologies of styrene oxide, a chiral aromatic system. We reach a definite assignment of four homochiral and two heterochiral dimers using auxiliary quantum chemistry calculations as well as structure-solving methods based on experimental isotopic information. A complete picture of the dimer conformational space is obtained, and plausible routes for conformational relaxation are derived. Molecular structures are discussed in terms of conformational flexibility, the concerted effort of weak intermolecular interactions, and their role in the...

The kinetics of styrene-free radical bulk polymerization was studied by differential scanning calorimetry (DSC). The data obtained from DSC thermograms were used to model and predict the autoacceleration during styrene polymerization and to understand how it is influenced by temperature. The experimental data were well described by the estimated kinetic model. The model included two processes (the first-order reaction and autoacceleration), because they occur simultaneously as two parallel reactions rather than being strictly separated. It was found that the autoacceleration activation energy is approximately four times lower than the energy of the first-order reaction.