Student Number : 0110634H - MPH research report - School of Public Health - Faculty of Sciences / During October 1996 to December 1999, isocyanates were the most frequently reported causative agent for occupational asthma cases (16.7% of all cases) submitted to the Surveillance of Work-Related and Occupational Respiratory Diseases in South Africa registry (SORDSA). Occupational disease surveillance registries in other countries also identified isocyanates as the most important occupational sensitiser. Asthma caused by isocyanates exposure may be severe and may persist even after exposure ceases. For this reason, it is important to identify the potentially hazardous isocyanate exposure settings, and to prevent sensitisation and asthma development where possible. Auto body repair shops, typically small, medium or micro enterprises (SMMEs), were the focus group in this study. Due to the paucity of medical surveillance and occupational hygiene programmes, there is likely to be over-exposure to isocyanates in such workplaces. The aim of this study was to identify and quantify exposure to HDI in auto body repair shops, and secondly, to describe the control measures currently used in these repair shops. The study investigated hexamethylene diisocyanate (HDI) exposure in the spray-painting processes of automotive repair shops in Gauteng. The repair shops were selected from the Highveld South African Motor Body Repairers’ Association (SAMBRA) membership list. Ten repair shops were included in this cross sectional study. Twelve subjects directly or indirectly involved in spray-painting in each repair shop had HDI exposure measured, resulting in a total of 113 HDI measurements. HDI monomers, prepolymers and total isocyanates determined using the National Institute for Occupational Safety and Health (NIOSH) draft method 5525 for analysis of monomeric and TRIG aliphatic isocyanates. Eighty one percent of workers were over-exposed to HDI monomers (exposure limit of 0.02mg/m3) and 3.4% to HDI prepolymers (exposure limit of 0.5mg/m3). Ninety percent of the establishments’ HDI monomer airborne concentration exceeded the OEL and 30% the prepolymer HDI concentrations. Workers were divided into 12 occupation categories according to the extent of their direct contact with the HDI-based paint and the three highest exposed groups were panel beaters, spray painters and dent-fillers. Workers directly and indirectly in contact with paint, in the auto body repair shops registered with SAMBRA were exposed to high levels of HDI during the spray painting operation. Insufficient and incorrect control measures were in place to control HDI exposure. The findings of this study confirm the risk of exposure to HDI in the automotive repair industry and the need for occupational hygiene control measures. In conclusion, high concentrations of HDI were common and even indirectly exposed workers were at risk of excessive exposure to HDI. Inadequate exposure control methods were widespread.

Diisocyanates are very reactive low molecular weight chemicals that are widely used in the manufacture of polyurethane products. Diisocyanate exposure is one of the most commonly reported causes of occupational asthma. Although diisocyanates have been identified as causative agents of respiratory diseases, the specific mechanisms by which these diseases occur remain largely unknown. Tandem mass spectrometry was used to unambiguously identify the binding site of isocyanates within four model peptides (Leu-enkephalin (Leu-enk, YGGFL), Angiotensin I (DRVYIHPFHL), Substance P-amide (RPKPQQFFGLM-NH2), and Fibronectin-adhesion promoting peptide (FAPP, WQPPRARI)). In each case, isocyanates were observed to react to the N-terminus of the peptide. No evidence of side chain/isocyanate adduct formation exclusive of the N-terminus was observed. However, significant intra-molecular diisocyanate crosslinking between the N-terminal amine and a side chain amine group was observed for arginine, when located within two residues of the N-terminus. Addition of multiple isocyanates to the peptide occurs via polymerization at the N-terminus, rather than addition of multiple isocyanate molecules to varied residues within the peptide. Toluene diisocyanate (TDI)-specific monoclonal antibodies (mAbs) with potential use in immunoassays for exposure and biomarker assessments were produced. A total of 59 unique mAbs were produced (29 IgG1, 14 IgG2a, 4 IgG2b, 2 IgG3 and 10 IgM) against 2,4 and 2,6 TDI bound protein. The reactivities of these mAbs were characterized by a solid phase indirect enzyme-linked immunosorbent assay (ELISA), Dot ELISA and Western immunoblot against various monoisocyanate, diisocyanate and dithioisocyanate protein conjugates. A subset of the mAbs were specific for 2,4 or 2,6 TDI-conjugated proteins only while others reacted to multiple dNCO conjugates including methylene diphenyl diisocyanate- and hexamethelene diisocyanate- human serum albumin . Western blot analyses demonstrated that some TDI conjugates form inter- and intra-molecular links resulting in multimers and a change in the electrophoretic mobility of the conjugate. In general, 2,4/2,6 TDI reactive mAbs displayed (1) stronger recognition of monoisocyanate haptenated proteins when the isocyanate was in the ortho position relative to the tolyl group, and were able to discriminate between (2) isocyanate and isothiocyanate conjugates (i.e. between the urea and thiourea linkage); and (3) between aromatic and aliphatic diisocyanates. The mAbs produced were not carrier protein specific with estimated affinity constants toward toluene diisocyanate conjugated human serum albumin ranging from 2.21 x 107 to 1.07 x 1010 M-1 for IgG mAbs. Studies using TDI vapor exposed lung and epithelial cell lines suggest potential utility of these mAbs for both research and biomonitoring of isocyanate exposure.

No description available.

Ce travail de thèse a porté sur la synthèse et la caractérisation de dispersions aqueuses de polyuréthane. Les matières premières envisagées pour la synthèse ont tout d'abord été caractérisées et un procédé de fabrication adapté a été mis en place. Des dispersions de polyuréthane commerciales et leurs polymères ont aussi été caractérisés, afin d'établir une référence en terme de propriétés physico-chimiques (taille de particules, viscosité, température de transition vitreuse, énergie de surface). Les dispersions aqueuses de polyuréthane ont ensuite été synthétisées. Différents paramètres ont été analysés, tels que la nature du diisocyanate, le rapport NCO/OH, la nature du (ou des) diol(s) et leurs poids moléculaire, la proportion d'agent émulsifiant et son degré de neutralisation. Toutes ces dispersions ainsi que leurs polymères ont enfin été caractérisés afin de mettre en évidence des relations structures-propriétés.

The desirable properties of polyurethanes (PUs) such as mechanical flexibility associated with chemical versatility make these polymers attractive in the development of biomedical devices. In this study, various segmented polyurethanes were synthesized through polymerization reactions between polycaprolactone (PCL) diol or triol and excess hexamethylene diisocyanate (HDI) with varying NCO/OH ratios and the effect of composition on the properties of the resultant polyurethane films were examined. Initially, isocyanate terminated prepolymers were synthesized through one-shot polymerization, and then these prepolymers were cured by introducing crosslinkages into the structure and thus PUs were obtained. In order to enhance biocompatibility and hydrophilicity of the resulting polymers, heparin was added into the prepolymer before the curing process. The influence of excess HDI as a crosslinker on the degree of H-bond formation between hard-hard segments or hard-soft segments was examined by using Fourier transform infrared-Attenuated total reflectance spectroscopy (FTIR-ATR). Also the effects of HDI content on the chemical, physical and mechanical properties of the polyurethanes were examined with differential scanning calorimetry (DSC), X-Ray diffraction spectroscopy (XRD), dynamic mechanical analyzer (DMA), mechanical tester and goniometer. FTIR- ATR, DSC and DMA analyses showed that use of triol resulted in better network formation and homogenous distribution of hard segments within soft segment matrix. Incorporation of heparin into the polymer matrix produced more hydrophilic films (water contact angle reduced from 80 to 60). Polyurethanes from PCL and HDI in the absence of any solvent, initiator, catalyst or chain extender were successfully synthesized and this kind of synthesis enhanced biocompatibility and increased the potential of polymers for use in biomedical applications.

Zugl.: Hamburg, Univ., Diss., 2008

In this study, a series of denim fiberboards are fabricated using two different resins, malamine urea formaldehyde (MUF) and polymeric methylene diphenyl diisocyanate (pMDI). Two experimental design factors (1) adhesive content and (2) MUF-pMDI weight ratio, were studied. All the denim fiberboard samples were fabricated following the same resin blending, cold-press and hot-press procedures. The physical and mechanical tests were conducted on the fiberboard following the procedures described in ASTM D1037 to obtain such as modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB), thickness swell (TS), and water absorption (WA). The results indicated that the MOE was significantly affected by both factors. IB was affected significantly by weight ratio of different glue types, with 17 wt% more MDI resin portion in the core layer of the denim boards, the IB for total adhesive content 15% fiberboard was enhanced by 306%, while for total adhesive content 25% fiberboard, enhanced by 205%. TS and WA, with higher adhesive content used in denim boards' fabrication, and more pMDI portion in the core layer of the boards, the boards' TS and WA was reduced by up to 64.2% and 78.8%, respectively.

Diisocyanates (dNCO) such as methylene diphenyl diisocyanate (MDI) are used primarily as cross-linking agents in the production of polyurethane products such as paints, elastomers, coatings and adhesives, and are the most frequently reported cause of chemically induced immunologic sensitization and occupational asthma (OA). Immune mediated hypersensitivity reactions to dNCOs include allergic rhinitis, asthma, hypersensitivity pneumonitis and allergic contact dermatitis. There is currently no simple diagnosis for the identification of dNCO asthma due to the variability of symptoms and uncertainty regarding the underlying mechanisms. Immunological sensitization due to dNCO exposure is traditionally thought to require initial conjugation of the dNCO to endogenous proteins to generate neoantigens, which trigger production of dNCO specific T lymphocytes and ultimately dNCO specific IgE. Testing for dNCO-specific IgE, for diagnosis of dNCO asthma is however, only specific (96-98%) but not sensitive (18-27%). The low prevalence of detectable dNCO specific IgE has been attributed to both assay limitations and a potential IgE-independent dNCO asthma mechanism(s). The identity of the conjugated proteins responsible for the sensitization also remains unknown. It is also not clear whether dNCOs bind to extracellular, cell membrane, or intracellular proteins as a way of triggering non-IgE asthma. Standardization and optimization of immunoassays used to screen for dNCO specific antibodies in sera is important if its utility as a dNCO asthma diagnostic tool is to be achieved. This will potentially improve sensitivity and allow comparison of results across studies. Current studies on assays of dNCO-specific IgE and IgG lack or have limited characterization of the conjugates used. Diisocyanates bound to hemoglobin (Hb), human serum albumin (HSA), and THP-1 proteins were quantified by HPLC with fluorescence detection. Proteomic tandem mass spectrometry (MS) was used to delineate TDI and MDI specific amino acid binding sites on Hb as well as identification of proteins from MDI exposed THP-1 cells. The trinitrobenzene sulfonic acid assay (TNBS) and SDS gel electrophoresis were used to evaluate extent of intra and intermolecular cross-linking in dNCO-HSA conjugates. Binding of monoclonal antibodies (mAbs) to dNCO bound proteins in enzyme-linked immunosorbent assay (ELISA) was used to evaluate antigenicity of dNCO-protein conjugates. The amount of dNCO binding to HSA and Hb increased with the concentration of the dNCO used for conjugation. All the dNCOs reacted with HSA more than with Hb. Eight binding sites were observed with both MDI and TDI on Hb. The N-terminal valines of both the alpha and beta subunits on Hb, lysine 40 of the alpha subunit and lysine 61 of the beta subunit were common binding sites for both TDI and MDI. Lysine 7 of the alpha subunit and lysines 8, 65 and 66 of the beta subunit were unique to MDI. On the other hand, lysines 11, and 16 of the alpha subunit and lysines 17 and 144 of the beta subunit were unique to TDI. Protein bound MDI was detected in a dose-dependent manner in membrane and cytoplasm fractions of MDI exposed THP-1 cells. MDI was also detected in 11 of the 13 cytoplasmic protein bands. The extent of MDI intracellular protein binding was not affected by cytochalasin D, a chemical that binds actin filaments and inhibits active uptake into cells. The extent of cross-linking shown using the TNBS assay was found to increase with amount of dNCO used. Clear bands from both intra and intermolecular cross-linking were observed on all dNCO-Hb/HSA SDS gels. Using ELISA, both TDI-Hb and TDI-HSA conjugates were reactive to monoclonal antibodies produced against TDI conjugated HSA indicating that dNCO-Hb is also antigenic. The best characterization of dNCO-protein conjugates is achieved by the quantitative determination of conjugated dNCO per mole of protein as well as determining the extent of dNCO cross-linking. Although HSA is more reactive to dNCOs than other serum proteins such as Hb, contribution from other serum proteins to development of OA should not be overlooked as dNCO-Hb was found to be reactive to dNCO specific mAbs. dNCO-conjugated proteins identified in the soluble fraction of MDI exposed THP-1 cells were all of intracellular origin suggesting that MDI can cross the cell membrane and react with intracellular proteins. The entry of MDI into live cells is a passive process, as the extent of intracellular binding was not affected by cytochalasin D. The present study support the potential involvement of dNCO-haptenated membrane and intracellular proteins in development of non-IgE dNCO asthma.

Submitted by José Eduardo Estevam da Silva (eduardoposmat@gmail.com) on 2018-04-15T21:56:51Z No. of bitstreams: 1 DISSERTAÇÃO VERSÃO FINAL.pdf: 4070557 bytes, checksum: fb263583bfb8f6573957500e76dce18a (MD5) / Approved for entry into archive by Minervina Teixeira Lopes null (vina_lopes@bauru.unesp.br) on 2018-04-16T19:34:27Z (GMT) No. of bitstreams: 1 silva_jee_me_bauru.pdf: 3974286 bytes, checksum: c0b61a56b4e52184bb3bdb58c2d99f52 (MD5) / Made available in DSpace on 2018-04-16T19:34:27Z (GMT). No. of bitstreams: 1 silva_jee_me_bauru.pdf: 3974286 bytes, checksum: c0b61a56b4e52184bb3bdb58c2d99f52 (MD5) Previous issue date: 2018-01-26 / O processo de fabricação de painéis MDF é muito dinâmico e a todo instante surgem novidades tecnológicas buscando não somente otimizar custos de processo, mas incrementar novas características ou melhorar a resistência mecânica e usinabilidade. As fibras de madeira de eucalipto e as resinas termofixas como a uréia-formaldeído desempenham papel importantíssimo no contexto industrial. Um grande número de pesquisas e estudos se direciona a aperfeiçoar os processos de fabricação por meio do aprimoramento da matéria-prima. Muitos materiais foram desenvolvidos e adicionados tanto as fibras como as resinas sendo muito comum a busca por melhorias na resistência mecânica nas chapas MDF. A resina MDI (metileno difenil diisocianato), por exemplo, possui muitas vantagens conhecidas como a isenção de emissão de formol e a alta resistência a água, porém, outras características relacionadas à interação química com a madeira são pouco estudadas. Nesse contexto tecnológico, o presente trabalho se dedicou ao uso das técnicas termoanalíticas TG/DTG-DTA e DSC para investigar e compreender melhor a interação química entre as fibras de madeira de eucalipto e as resinas sintéticas termofixas e por fim, sugerir melhorias ao processo produtivo buscando assim, reduzir custos de fabricação. Além das técnicas termogravimétricas, a espectroscopia vibracional de absorção na região infravermelho médio com transformada de Fourier também foi usada para auxiliar na proposta reacional de polimerização e principalmente na identificação da estrutura química dos produtos gerados. Investigou-se também o processo de polimerização térmica do monômero MDI bem como sua degradação térmica seguindo as recomendações do ICTAC. As curvas TG/DTG-DTA mostraram que a polimerização foi incompleta em todas as resinas indicando a necessidade de ajustes no processo. A proposta reacional para as resinas UF e MDI está de acordo com os dados das curvas TG e espectros de MIR. A partir da polimerização da resina MDI sugeriu-se a formação de carbodiimidas como produto final. Ao final da pesquisa, algumas melhorias foram propostas como o aumento da temperatura da prensa e a diminuição da concentração de resina visto que na situação atual, a polimerização é incompleta e deixa resíduos nas chapas MDF. Comprovou-se também que as chapas fora de especificação podem ser usadas como biomassa combustível nas caldeiras em substituição ao cavaco de eucalipto, pois liberam mais calor quando estão em combustão. / The process of manufacturing MDF panels is very dynamic and at every moment technological innovations are emerging, seeking not only to optimize process costs, but to increase new characteristics or improve mechanical strength and machinability. Eucalyptus wood fibers and thermoset resins such as urea-formaldehyde play a very important role in the industrial context. A great number of researches and studies are directed at perfecting the manufacturing processes through the improvement of the raw material. Many materials have been developed and added to both fibers and resins, and the search for improvements in mechanical strength in MDF sheets is very common. MDI resin (methylene diphenyl diisocyanate), for example, has many advantages known as formaldehyde emission exemption and high water resistance, but other characteristics related to the chemical interaction with wood are little studied. In this technological context, the present work was dedicated to the use of TG / DTG-DTA and DSC thermoanalytical techniques to investigate and better understand the chemical interaction between eucalyptus wood fibers and thermosetting synthetic resins and, finally, to suggest improvements to the production process thus seeking to reduce manufacturing costs. In addition to the thermogravimetric techniques, the vibrational absorption spectroscopy in the medium infrared region with Fourier transform was also used to aid in the polymerization reaction proposal and mainly in the identification of the chemical structure of the generated products. The thermal polymerization process of the MDI monomer as well as its thermal degradation following the recommendations of the ICTAC were also investigated. The TG / DTG-DTA curves showed that the polymerization was incomplete in all resins indicating the need for process adjustments. The reaction proposal for the UF and MDI resins is in agreement with the data of the TG curves and MIR spectra. From the polymerization of MDI resin the formation of carbodiimides was suggested as the final product. At the end of the research, some improvements were proposed, such as the increase in the temperature of the press and the decrease of the resin concentration, since in the current situation the polymerization is incomplete and leaves residues in the MDF sheets. It has also been proven that non-specification sheets can be used as biomass fuel in boilers instead of eucalyptus chips, as they release more heat when they are in combustion.

Made available in DSpace on 2014-12-17T15:41:41Z (GMT). No. of bitstreams: 1 OldemarRC.pdf: 2134736 bytes, checksum: bf80e72f9b5d1ebc0b3148367e30383f (MD5) Previous issue date: 2007-10-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The aim of this work was the preparation of polyols from reactions between castor oil and dietanolamine to increase the hydroxyl content and the network degree in the products to application in electronic devices. The polyols and the mixtures obtained were characterized by nuclear magnetic ressonance. Castor oil (CO) is a natural triglyceride - based polyol possessing hydroxyl groups, which allow several reactions that produce many different products. Among them are the polyurethanes (PU), which have been considered an ideal product for the covering of electricelectronic circuits, due to their excellent electrical, shock-absorbing, solvents resistance and hydrolytic stability properties. About 90% of the fatty acids present in the castor oil are ricinoleic acid (12-hydroxyoleic acid), while the remaining 10% correspond to non-hydroxylated fatty acids, mainly linoleic and oleic acids. The chemical analysis of castor oil indicates a hydroxyl number of 2.7. In this work, a polyol was obtained by the reaction of the CO with diethanolamine (DEA), in order to elevate the hydroxyl value from 160 to 230 or to 280 mgKOH/g, and characterized by nuclear magnetic resonance (NMR) 1H and 13C (Mercury 200). The polyadition of the resulting polyol with isophorone diisocianate (IPDI) was carried out at 60?C, and the reaction kinetics was followed by rheological measurements in a Haake RS150 rheometer. The electrical properties were determined in a HP LCR Meter 4262A, at 1.0 Hz and 10.0 KHz. The chemical analysis showed that the polyols obtained presented hydroxyl number from 230 to 280 mgKOH/g. The polyadition reaction with IPDI produced polyurethane resins with the following properties: hardness in the range from 45 shore A to 65 shore D (ASTM D2240); a dielectric constant of 3.0, at 25?C (ASTM D150). Those results indicate that the obtained resins present compatible properties to the similar products of fossil origin, which are used nowadays for covering electric-electronic circuits. Therefore, the PUs from castor oil can be considered as alternative materials of renewable source, free from the highly harmful petroleum - derived solvents / O presente trabalho teve como objetivo a obten??o de poli?is a partir das rea??es do ?leo de mamona (OM) com dietanolamina (DEA), visando elevar o ?ndice de hidroxila e consequentemente o grau de reticula??o dos produtos finais, cuja aplica??o se destinou ao encapsulamento de circuitos eletroeletr?nicos. A caracteriza??o desses poli?is e respectivas misturas foram feitas utilizando-se a t?cnica da resson?ncia magn?tica nuclear (NMR). O OM (triglicer?deo do ?cido ricinoleico) ? um poliol vegetal natural por apresentar grupo funcional hidroxila que permite v?rias rea??es e produ??o de diferentes produtos. Entre eles est?o as poliuretanas (PU) que t?m sido consideradas como produtos ideais para encapsulamento de componentes de circuitos eletro-eletr?nicos, devido as suas excelentes propriedades com rela??o ? resist?ncia mec?nica e qu?mica. As poliuretanas derivadas do ?leo de mamona podem ser consideradas materiais alternativos de fonte renov?vel e, para as produzidas neste trabalho, n?o foram empregados nenhum tipo de solvente. Cerca de 90% dos ?cidos graxos que comp?em o ?leo de mamona s?o ?cido ricinoleico (?cido 12-hidroxioleico), enquanto os outros 10% s?o ?cidos graxos n?o hidroxilados (?cidos linoleico e oleico). As an?lises qu?micas do ?leo de mamona indicam uma funcionalidade m?dia de 2,7, em rela??o aos grupos hidroxila. A poliadi??o entre o poliol resultante e o isocianato de isoforona (IPDI) teve sua cin?tica aco mpanhada com o aux?lio do re?metro Haake RS 150 ? temperatura de 60 ?C. As propriedades el?tricas foram determinadas em uma ponte HP LCR Meter 4262 A a 1,0 Hz e 10,0 KHz. As an?lises qu?micas mostraram que os poli?is obtidos apresentaram ?ndice de hidroxila entre 230 e 280 mgKOH/g. A rea??o de poliadi??o com IPDI produziu resinas de poliuretana com as seguintes propriedades: dureza entre 45 e 65 shore D (ASTM D2240); constante diel?trica de 3,0 a 25 ?C (ASTM D150). Os resultados, de um modo geral, indicaram que as resinas, cujo extensor de cadeia foi a DEA, apresentaram propriedades compat?veis e em muitos casos superiores, quando comparadas ?s dos produtos atualmente dispon?veis no mercado, sintetizados ? base de trietanolamina (TEA)