Toluenediamines Research Articles

Computational and Experimental Method for Evaluating the Reactivity of Substituted Toluene Diamines and Azo Compounds in the Reactions of Amine and Anhydride Curing of Epoxy Resins

The optimization of the molecular structure of substituted 3,5-toluylene diamines was carried out by the ab initio method, which made it possible to calculate the volume of stretching vibrations and the steric factor of the ethyl and methylthiol substituents on the basis of the data obtained on the bond lengths and bond angles. A linear dependence of the total steric factor of substituents in the molecules of substituted 3,5-toluylene diamines on the activation energy of the reaction of their polyaddition with novolac epoxy resin was established. For 4-phenylazophenol, 4-methoxyazobenzene, 4-phenylazo-N,N ʹ-dimethylaniline, 1-(2-pyridylazo)-2-naphthol, phenylazo-4-naphthylamine, studied as catalysts for the polyaddition of isomethyltetrahydrophthalic anhydride to epoxy resin, dependence of the activation energy on the value of the electron density is observed at the nitrogen atom of the azo group. The derived linear dependences evidence the established latency of epoxy binders, which depends mainly on hardeners and catalysts. Using a computational and experimental method for evaluating the reactivity of hardeners and catalysts, heat-resistant polymers and composites with good physical-mechanical and thermomechanical characteristics were produced, which meet modern requirements for products operating in a wide temperature range.

Erratum to "Comparison between Different Extraction Methods for Determination of Primary Aromatic Amines in Food Simulant".

[This corrects the article DOI: 10.1155/2018/1651629.].

Comparison between Different Extraction Methods for Determination of Primary Aromatic Amines in Food Simulant.

The primary aromatic amines (PAAs) are food contaminants which may exist in packaged food. Polyurethane (PU) adhesives which are used in flexible packaging are the main source of PAAs. It is the unreacted diisocyanates which in fact migrate to foodstuff and then hydrolyze to PAAs. These PAAs include toluenediamines (TDAs) and methylenedianilines (MDAs), and the selected PAAs were 2,4-TDA, 2,6-TDA, 4,4′-MDA, 2,4′-MDA, and 2,2′-MDA. PAAs have genotoxic, carcinogenic, and allergenic effects. In this study, extraction methods were applied on a 3% acetic acid as food simulant which was spiked with the PAAs under study. Extraction methods were liquid-liquid extraction (LLE), dispersive liquid-liquid microextraction (DLLME), and solid-phase extraction (SPE) with C18 ec (octadecyl), HR-P (styrene/divinylbenzene), and SCX (strong cationic exchange) cartridges. Extracted samples were detected and analyzed by HPLC-UV. In comparison between methods, recovery rate of SCX cartridge showed the best adsorption, up to 91% for polar PAAs (TDAs and MDAs). The interested PAAs are polar and relatively soluble in water, so a cartridge with cationic exchange properties has the best absorption and consequently the best recoveries.

Determination of isocyanate specific albumin-adducts in workers exposed to toluene diisocyanates

Toluene diisocyanates (2,4-TDI and 2,6-TDI) are important intermediates in the chemical industry. Among the main damages after low levels of TDI exposure are lung sensitization and asthma. It is therefore necessary to have sensitive and specific methods to monitor isocyanate exposure of workers. Urinary metabolites or protein adducts have been used as biomarkers in workers exposed to TDI. However, with these methods it was not possible to determine if the biomarkers result from exposure to TDI or to the corresponding toluene diamines (TDA). This work presents a new procedure for the determination of isocyanate-specific albumin adducts. Isotope dilution mass spectrometry was used to measure the adducts in albumin present in workers exposed to TDI. 2,4-TDI and 2,6-TDI formed adducts with lysine: Nϵ-[({3-amino-4-methylphenyl}amino)carbonyl]-lysine, Nϵ-[({5-amino-2-methylphenyl}amino)carbonyl]-lysine, and Nϵ- [({3-amino-2-methylphenyl}amino)carbonyl]-lysine. In future studies, this new method can be applied to measure TDI-exposures in workers.

Protein adducts as biomarkers of exposure to aromatic diisocyanates in workers manufacturing polyurethane (PUR) foam

This work was undertaken to investigate the usefulness of diisocyanate-related protein adducts in blood samples as biomarkers of occupational exposure to toluene diisocyanate (TDI; 2,4- and 2,6-isomers) and 4,4'-methylenediphenyl diisocyanate (MDI). Quantification of adducts as toluene diamines (TDAs) and methylenedianiline (MDA) was performed on perfluoroacylated derivatives by gas chromatography-mass spectrometry (GC-MS/MS) in negative chemical ionisation mode. TDI-derived adducts were found in 77% of plasma and in 59% of globin samples from exposed workers manufacturing flexible polyurethane foam. The plasma levels ranged from 0.003 to 0.58 nmol mL(-1) and those in globin from 0.012 to 0.33 nmol g(-1). The 2,6-isomer amounted to about two-thirds of the sum concentration of TDA isomers. MDI-derived adducts were detected in 3.5% of plasma and in 7% of globin samples from exposed workers manufacturing rigid polyurethane foam. A good correlation was found between the sum of TDA isomers in urine and that in plasma. The relationship between globin adducts and urinary metabolites was ambiguous. Monitoring TDI-derived TDA in plasma thus appears to be an appropriate method for assessing occupational exposure. Contrary to TDI exposure, adducts in plasma or globin were not useful in assessing workers' exposure to MDI. An important outcome of the study was that no amine-related adducts were detected in globin samples from TDI- or MDI-exposed workers, alleviating concerns that TDI or MDI might pose a carcinogenic hazard. Further studies are nevertheless required to judge whether diisocyanates per se could be such a hazard.

Microwave-assisted acid hydrolysis of toluene diamine conjugates in urine samples for biomarkers in toluene diisocyanate analysis

Toluene diamines (TDAs) in urine have been used widely to determine the amount of toluene diisocyanate (TDI) absorbed by humans. Conventional hydrolysis to prepare a sample of urine takes approximately 16 h. An attempt is made to apply microwave-assisted heating (MAH) to reduce the duration of analysis. Urine collected from rats exposed to a mixture of 2,4- and 2,6-TDI was diluted with non-exposed human urine 1/1250-, 1/500- and 1/250-fold. The urine samples were hydrolyzed by both conventional heating and MAH. The hydrolysis efficiency obtained using MAH significantly exceeded that obtained using conventional heating. Hydrolysis by MAH required only 20 min, 48 times faster than with conventional heating. The use of the MAH method in hydrolysis was demonstrated to be reproducible, timesaving and efficient technique in measuring the concentration of urinary TDAs.

Isocyante Emissions: A Review of Work on Environmental Aspects of Handlin, Toluene Diisocyanate

Experimental work has been carried out on three aspects of handling toluene diisocyanate (TDI): (i) The quantities of TDI emitted from polyurethane foam plants are low: of the order of 0·005% of the TDI fed to the process is subsequently discharged to the atmosphere. The destruction of this TDI by chemical reactions in the atmosphere it still under examination. All results so far indicate that no toluene diamines are formed. (ii) Trials with an activated carbon scrubber installed on the vent line of a foam plant indicate that substantial amounts of TDI can be removed from the discharged air. More work is needed before an economic assessment of the process can be made. (iii) Field trials on fire fighting techniques for TDI spillages show that proteinic type fire fighting foams give the best suppression of TDI vapours.