Toluene Diisocyanate Research Articles

Photocatalytic-proxone process application in the degradation of toluene-diisocyante, and methylene diphenyl diisocyanate from polluted air

Isocyanates are one of the most widely used semi-volatile compounds in various industries, including the polyurethane industry. Applying a hybrid advanced oxidation process to the degradation of toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI) from polluted air were the main aims of the study. The BiOI@MOF/Zeolite nanocomposite was prepared by the solvothermal method. XRD, FT-IR, FESEM, EDAX, EDS element mapping, TEM, BET, XPS, and UV–vis spectra analysis were applied to indicate the nanocomposite characters. The effect of flow, ozone concentration, hydrogen peroxide concentration, initial isocyanates concentration, and relative humidity were investigated. The concentration of isocyanates measurement via NIOSH 5522 standard method. In the optimum conditions of the process, the supplementary studies were done. The results of the analysis of composite structure indicated that well synthesized had been done. Experimental results showed optimal operating conditions could degrade more than 90 % of isocyanates. The synergistic effect coefficient of the mechanisms was 2.03 and 2.34 for TDI and MDI, respectively. The stability of the process was observed in 6 consecutive steps. The residual ozone concentration in the system's outlet was negligible (0.047 mg/l). The CO2 and CO emissions proved that the mineralization of isocyanates occurred. The theoretical mineralization rate was 0.64 and 0.55 reported for TDI and MDI, respectively. The simultaneous presence of MDI and TDI in the reactor decreases the efficiency of the process. The pure oxygen gas, pure nitrogen gas, and atmospheric as a carrier gas showed different performances in the process of isocyanate removal (80.8, 35.4, and 61.7 % degradation in the simultaneous presence of MDI and TDI).

THE AVAILABLE CURING AGENTS FOR POLY(3-DIFLUOROAMINOMETHYL-3-METHYLOXETANE/3,3-BIS-AZIDOMTHYLOXETANE) (PDB) OBTAINED THROUGH THE CURING REACTION STUDY OF PDB AND ISOCYANATE

The difluoroamino polymer poly(3-difluoroaminomethy l-3-methyloxetane/3,3-bis-azidomethylox-etane) (PDB) can be an excellent energetic binder in the composite solid propellant, while it has no practical application in curing yet. This study tried isophorone diisocyanate (IPDI), N-100, toluene diisocyanate (TDI), diphenyl methane diisocyanate (MDI), and naphthalene diisocyanate (NDI) to react with PDB, respectively. The ideal curing agent for PDB can form the carbamate structure (-NH-COO-), and the difluoroamino group (-NF<sub>2</sub>) was not destroyed in reactions. Fourier transform infrared, <sup>13</sup>C NMR, and <sup>1</sup>H nuclear magnetic resonance (NMR) was used to analyze the reactions between PDB and isocyanates. The curing reaction kinetics of PDB/TDI, the mechanical performance of PDB/TDI film, and the chemical changes in PDB/TDI reaction were studied separately. The results showed no carbamate structure formed during the reactions with aliphatic isocyanates (IPDI, N-100). In PDB/N-100 reaction, the -NF<sub>2</sub> was destroyed. Aromatic isocyanates (TDI, MDI, and NDI) have higher reactivity, formed carbamate structures in the curing reactions, and no -NF<sub>2</sub> was destroyed. Therefore, TDI, MDI, and NDI can be used as curing agents for PDB. The E<sub>α</sub> of PDB/TDI curing reaction was 42.4189 kJ/mol<sup>-1</sup>, and PDB/TDI films exhibit outstanding mechanical properties.

Supramolecular Cu(ii) nanoparticles supported on a functionalized chitosan containing urea and thiourea bridges as a recoverable nanocatalyst for efficient synthesis of 1H-tetrazoles.

A cost-effective and convenient method for supporting of Cu(ii) nanoparticles on a modified chitosan backbone containing urea and thiourea bridges using thiosemicarbazide (TS), pyromellitic dianhydride (PMDA) and toluene-2,4-diisocyanate (TDI) linkers was designed. The prepared supramolecular (CS-TDI-PMDA-TS-Cu(ii)) nanocomposite was characterized by using Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), thermogravimetry/differential thermogravimetry analysis (TGA/DTA), energy-dispersive X-ray spectroscopy (EDS), EDS elemental mapping and X-ray diffraction (XRD). The obtained supramolecular CS-TDI-PMDA-TS-Cu(ii) nanomaterial was demonstrated to act as a multifunctional nanocatalyst for promoting of multicomponent cascade Knoevenagel condensation/click 1,3-dipolar azide-nitrile cycloaddition reactions very efficiently between aromatic aldehydes, sodium azide and malononitrile under solvent-free conditions and affording the corresponding (E)-2-(1H-tetrazole-5-yl)-3-arylacrylenenitrile derivatives. Low catalyst loading, working under solvent-free conditions and short reaction time as well as easy preparation and recycling, and reuse of the catalyst for five consecutive cycles without considerable decrease in its catalytic efficiency make it a suitable candidate for the catalytic reactions promoted by Cu species.

Fabrication and evaluation of epoxy resin film adhesive with excellent heat resistance and potential flame retardance

To obtain a heat-resistant and flame-retardant epoxy film system that can be stored for a long time, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was used to modify an imidazole curing agent, and thus a new reactive flame retardant curing agent (DMH) was successfully synthesized. A phenolic epoxy resin matrix with an oxazolidinone (EPO) structure was synthesized through the reaction of a phenolic epoxy resin (EPN) and toluene diisocyanate (TDI), and polyethersulfone (PES) was used as a toughening agent. After characterization of the material, the curing process was also considered. The results showed that the film adhesive maintained reaction inertness around room temperature and was effectively cured at a curing temperature of 130 °C and released moderate heat. Cone calorimetry testing further confirmed the excellent flame retardance of the film adhesive. The T5% temperature obtained from thermogravimetric analysis (TGA) was as high as 366 °C, which proved its good thermal stability. On this basis, the mechanical properties of the film adhesive didn't decrease, and the addition of PES ensured its good toughness. When used as the adhesive for cured resin aluminum-honeycomb sandwich samples, the lap shear strength (LSS) of the sample reached 35.6 MPa. Due to these advancements, the film adhesive system has the potential for application in a wide range of fields.

THE STUDY OF INTERMOLECULAR INTERACTIONS IN THE POSS-CONTAINING NANOCOMPOSITES BASED ON POLYURETHANE AND POLYURETHANE/POLY(HYDROXYPROPYL METHACRYLATE) MATRICES

The nanocomposites based on polyurethane matrix and multicomponent polymer matrices consisting of polyurethane and poly(hydroxypropyl methacrylate) with different contents of the last, and 1,2-propanediolisobutyl polyhedral oligomeric silsesquioxane (1,2-propanediolisobutyl-POSS), which was used as a functionalized nanofiller, were synthesized. The influence of the content of 1,2-propanediolisobutyl-POSS on intermolecular interactions and structural features of the nanocomposites was investigated by the method of IR-spectroscopy with Fourier transformation and attenuated total reflection (FTIR-ATR). The study of thermal curing of the model system, which consists of the adduct of trimethylolpropane with toluene diisocyanate and 1,2-propanediolisobutyl-POSS, made it possible to conclude that 1,2-propanediolisobutyl-POSS participates in the reaction of urethane formation using of one of the terminal hydroxyl groups, and it is incorporated into the polymer chain between cross-linking of polyurethane networks. The investigation of multicomponent polymer matrices by FTIR-ATR spectroscopy was done and was shown that photopolymerization of second polymer poly(hydroxypropyl methacrylate) in the matrix of polyurethane was completed by the opening of a double bond and the formation of a linear polymer in the composition of semi-IPN. Studies of nanocomposites based on multicomponent polymer matrices consisting of polyurethane and poly(hydroxypropyl methacrylate) with 15 and 30 % of the last by FTIR-ATR spectroscopy demonstrated the presence of POSS in the nanocomposites and the influence of POSS content on the structure of the studied systems and on the degree of phase separation. The POSS is "embedded" into the polymer chain between cross-linking of the polyurethane networks, with the additional formation of a complex system of intermolecular hydrogen bonds between the carboxyl and amine components of urethane groups in the nanocomposites.

Preparation and characterization of pesticide Fosthiazate‐loaded microcapsules for controlled release system

AbstractPreparation of Fosthiazate (FTZ)‐loaded microcapsules with controlled release was attempted by the interfacial polymerization using toluene diisocyanate (TDI) and triethylenetetramine (TETA) as monomers. The effects of the monomer concentration and the monomer concentration ratio on characteristics of the microcapsules such as size, shell thickness and release behavior in water and in soil were studied. In the study, FTZ was successfully encapsulated into a polyurea resin, and the characterization revealed that the microcapsule shell became thicker proportionally to the applied monomer concentration. The release rate of FTZ from the microcapsules in water was mostly proportional to the ratio of the surface area to the shell thickness of the microcapsules, and the release rate fitted the first‐order kinetic model. On the one hand, when TDI concentration was low or the monomer concentration ratio was high, the release rate was significantly increased owing to the formation of insufficient microcapsule shell and the coarseness of the shell. Moreover, the slower the release rate in water was, the higher residual ratio of FTZ in soil could be maintained. However, it was also observed that the release rate in soil was faster than that in water. It is suggested that the constant replacement of water around the microcapsules accelerated the release rate, or the microcapsule particles migrated through the soil. These results indicated that FTZ‐loaded microcapsules with controlled release were able to be prepared. In addition, basic findings about the relationship and the difference between the release behaviors of FTZ‐loaded microcapsules in water and in soil were obtained.

Reaction of OH with Aliphatic and Aromatic Isocyanates

Isocyanates are highly relevant industrial intermediates for polyurethane production. In this work, we used quantum chemistry and transition state theory (TST) to investigate the gas-phase reaction of isocyanates with the OH radical, which is likely one of the most significant chemical sinks for these compounds in the troposphere. para-Tolyl-isocyanate (p-tolyl-NCO) was chosen as a proxy substance for the large-volume aromatic diisocyanate species toluene diisocyanate and methylene diphenyl diisocyanate. Besides p-tolyl-NCO + OH, the model reactions CH3NCO + OH, H2C═CHNCO + OH, C6H5-NCO + OH, C6H5-CH3 + OH, and C6H6 + OH have been studied as well to analyze various substituent effects and to allow for comparison with literature. Quantum chemical computations at the CCSD(T)/cc-pV(T,Q → ∞)Z//M06-2X/def2-TZVP level were used as the basis for tunneling-corrected canonical TST calculations. For CH3NCO + OH, H abstraction by OH at the methyl group is the main reaction channel according to our calculations and predicted to be four orders of magnitude faster than OH addition at the NCO group. The calculated rate coefficient (8.8 × 10-14 cm3 molecule-1 s-1) at 298 K is in good agreement with experimental data from the literature. Likewise, for aromatic isocyanates, OH attack at the isocyanate group was found to be only a minor pathway compared to addition to the aromatic ring. In the OH + p-tolyl-NCO reaction, OH addition at the ortho-position relative to the NCO group has been identified as the main initial reaction channel (branching fraction: 53.2%), with smaller but significant branching fractions for the H abstraction at the methyl group (9.6%) as well as the other ring addition reactions (ipso: 2.3%, meta: 24.5%, para: 10.5%, all relative to the NCO group). By comparing OH addition to the aromatic ring in p-tolyl-NCO with the respective ring addition reactions of phenyl isocyanate and toluene, the site-selective reactivity trends observed for ring addition in the OH + p-tolyl-NCO could be rationalized by a dominating positive mesomeric effect of the NCO group and a positive electron-donating (inductive) effect of the CH3 group. Except for the OH ring adduct formed from OH addition in ipso-position to the NCO group, we estimate the first-generation radical intermediates in the OH + p-tolyl-NCO reaction to have sufficiently long lifetimes to react with O2 under atmospheric conditions and undergo typical oxidative reaction cascades like those known for benzene or toluene.

The Relationship Between Potential Occupational Sensitizing Exposures and Asthma: An Overview of Systematic Reviews.

The aim was to identify, appraise, and synthesize the scientific evidence of the relationship between potential occupational sensitizing exposures and the development of asthma based on systematic reviews. The study was conducted as an overview of systematic reviews. A systematic literature search was conducted for systematic reviews published up to 9 February 2020. Eligibility study criteria included persons in or above the working age, potential occupational sensitizing exposures, and outcomes defined as asthma. Potential occupational sensitizing exposures were divided into 23 main groups comprising both subgroups and specific exposures. Two reviewers independently selected studies, extracted study data, assessed study quality, and evaluated confidence in study results and level of evidence of the relationship between potential occupational sensitizing exposures and asthma. Twenty-seven systematic reviews were included covering 1242 studies and 486 potential occupational sensitizing exposures. Overall confidence in study results was rated high in three systematic reviews, moderate in seven reviews, and low in 17 reviews. Strong evidence for the main group of wood dusts and moderate evidence for main groups of mites and fish was found. For subgroups/specific exposures, strong evidence was found for toluene diisocyanates, Aspergillus, Cladosporium, Penicillium, and work tasks involving exposure to laboratory animals, whereas moderate evidence was found for 52 subgroups/specific exposures. This overview identified hundreds of potential occupational sensitizing exposures suspected to cause asthma and evaluated the level of evidence for each exposure. Strong evidence was found for wood dust in general and for toluene diisocyanates, Aspergillus, Cladosporium, Penicillium, and work tasks involving exposure to laboratory animals.

Immobilization of cobalt oxide nanoparticles on porous nitrogen-doped carbon as electrocatalyst for oxygen evolution

Highly efficient and robust electrocatalysts have been in urgent demand for oxygen evolution reaction (OER). For this purpose, high-cost carbon materials, such as graphene and carbon nanotubes, have been used as supports to metal oxides to enhance their catalytic activity. We report here a new Co 3 O 4 -based catalyst with nitrogen-doped porous carbon material as the support, prepared by pyrolysis of porous polyurea (PU) with Co(NO 3 ) 2 immobilized on its surface. To this end, PU was first synthesized, without any additive, through a very simple one-step precipitation polymerization of toluene diisocyanate in a binary mixture of H 2 O-acetone at room temperature. By immersing PU in an aqueous solution of Co(NO 3 ) 2 at room temperature, a cobalt coordinated polymer composite, Co(NO 3 ) 2 /PU, was obtained, which was heated at 500 °C in air for 2 h to get a hybrid, Co 3 O 4 /NC, consisting of Co 3 O 4 nanocrystals and sp 2 -hybridized N-doped carbon. Using this Co 3 O 4 /NC as a catalyst in OER, a current density of 10 mA·cm −2 was readily achieved with a low overpotential of 293 mV with a Tafel slope of 87 mV·dec −1 , a high catalytic activity. This high performance was well retained after 1000 recycled uses, demonstrating its good durability. This work provides therefore a facile yet simple pathway to fabrication of a new transition metal oxides-based N-doped carbon catalyst for OER with high performance.

Improvement in Migration Resistance of Hydroxyl-Terminated Polybutadiene (HTPB) Liners by Using Graphene Barriers.

The excessive migration of plasticizers leads to debonding and cracking of a liner, which can compromise the safety of a solid propellant. Graphene oxide (GO), with a laminar structure as a filler, can effectively reduce the migration of plasticizers. In this study, we modified GO using toluene diisocyanate (TDI). The cross-link density of the substrate was increased by grafting isocyanate groups to obtain a denser liner for the purpose of preventing plasticizer migration. We also used octadecylamine (ODA) to modify GO by grafting negatively charged amide groups on the GO surface. The electrostatic repulsive effect of the amide group on the plasticizer molecules was used to prevent plasticizer migration. Two modified GOs were filled into the hydroxyl-terminated polybutadiene to prepare two composite liners. We then investigated the migration resistance and migration kinetics of each modified liner using the dipping method. In addition, we explored the mechanical properties of each modified liner. Compared with the original liner, the anti-migration and mechanical properties of the modified composite liners were significantly improved. Among them, the TDI-modified liner had the most obvious improvement in migration resistance, while the ODA-modified liner had the greatest improvement in bonding properties. All types of liners met the requirements of the current propellant systems. This study provides an effective reference for improving the migration resistance and bonding properties of the composite liner.

New Method to Biomonitor Workers Exposed to 1,6-Hexamethylene Diisocyanate.

Isocyanates such as 1,6-hexamethylene diisocyanate (HDI), 4,4'-methylenediphenyl diisocyanate, and toluene diisocyanate are highly reactive compounds that have a variety of commercial applications, including manufacturing polyurethane foam, elastomers, paints, adhesives, coatings, insecticides, and many other products. Their primary route of occupational exposure is through inhalation. Due to their high chemical reactivity, they are toxic and have adverse effects at the cellular and subcellular levels, leading to irritative and immunological reactions associated with lung disease. High concentrations of isocyanates are strong respiratory irritants. Bronchial sensitization and asthma are among the major adverse clinical reactions associated with low-level chronic exposure to isocyanates. Albumin adducts have been linked to the mechanism of occupational asthma caused by isocyanates. Isocyanates react in vivo with albumin, which is recognized by the immune system. Albumin adducts of isocyanates trigger immune responses and are probably the antigenic basis for isocyanate asthma. Sensitization to isocyanates is the main pathway for adverse health effects. Therefore, markers for the biologically effective dose such as albumin adducts of HDI are needed. A new isocyanate adduct of HDI with lysine─Nε-[(6-amino-hexyl-amino)carbonyl]-lysine (HDI-Lys)─was synthesized and characterized by 1H-NMR, 13C-NMR, and mass spectrometry (MS). Appropriate internal standards─HDI-Lys-4,4'-5,5'-d4 (HDI-d4-Lys) and Nε-[(7-amino-heptyl-amino)carbonyl]-lysine (Hep-Lys)─were synthesized to establish a LC-MS/MS method for the analysis of HDI adducts in in vitro modified albumin and in workers. The presence of HDI-Lys was found after pronase digestion of albumin and confirmed by two independent chromatographic approaches: with a C8 reversed-phase column and with a hydrophilic interaction liquid chromatography column. Quantification was performed with positive electrospray ionization (ESI)-MS. The adduct peak found in vivo was confirmed with the less sensitive negative ESI-MS. In summary, these are new compounds and methods to determine isocyanate-specific adducts with albumin in workers exposed to HDI.

ASSESSMENT AND IDENTIFICATION OF POLYOL BASED ON PALM OIL AND NATURAL FILLING MATERIALS FOR RENEWABLE COATING PAINT APPLICATION

Chitosan/clay hybrid nanoparticles have been prepared as natural antibacterial and anticorrosion agents to enhance the protective function of polyurethane-based coating paints. Chitosan is a material with antibacterial properties because it contains acetamide group which is widely used for hygiene purposes in the medical field. Clay is a natural clay particle with a hollow structure that allows loading and release of active substances such as surfactant ions that can contribute to improving the properties of the material. The polyurethane in this study was obtained from palm oil oleic acid, which was processed into polyol, toluene diisocyanate was added to produce polyurethane. Coating paint is efficiently loaded with chitosan and clay active substances which are combined to form a hybrid composite. Based on the FTIR data of polyurethane showing the formation of a hydroxyl group on the palm oil epoxide compound, the reaction lasted for 2 hours at 60oC as evidenced by the absorption of the OH wave number which widened at 3305.99 cm-1. The value of the wavelength of the OH group in the bentonite sample before and after purification has decreased, proving that the intercalation of surfactants into the bentonite interlayer causes the hydrophilic nature of bentonite to change to hydrophobicity. The d-spacing layer of raw bentonite has a maximum reflection angle peak of 7.26o with a d-spacing value of 1.132 nm, and the d-spacing size increases to 1.631 nm at the peak of the maximum reflection angle of 4.49o after purification. The presence of absorption at 1064.71 cm-1 in shrimp shell chitosan indicates COC vibration.

Flexible Polyurethane Foams Reinforced by Functionalized Polyhedral Oligomeric Silsesquioxanes: Structural Characteristics and Evaluation of Thermal/Flammability Properties.

In this work, we report on flexible toluene diisocyanate (TDI)-based polyurethane foams (FPUFs) chemically modified by POSS moieties, i.e., octa (3-hydroxy-3-methylbutyldimethylsiloxy) POSS (OCTA-POSS) and 1,2-propanediolizo-butyl POSS (PHI-POSS). The influence of silsesquioxane on the PU foaming process, structure, morphology, physicochemical, and mechanical properties, as well as flammability, was examined. FT-IR analysis provided evidence for the chemical incorporation of the nanofiller into the foam structure. It was found that the addition of POSS increases the apparent density of the foam and its compressive strength. The XRD and SEM-EDS techniques showed the uniform distribution of POSS in the FPUF with agglomeration depending on the kind and content of the introduced POSS moieties. The analysis of the thermogravimetric and microcalorimetry data revealed an improved resistance to the burning of FPUFs containing reactive POSS, as evidenced by the reduced rate of heat release (HRR). Importantly, the mechanical properties tests showed that the incorporation of silsesquioxane nanoparticles into the polyurethane structure via covalent bonds strengthens the foam integrity.

Fabrication of multiwalled carbon nanotube‐reinforced rapeseed‐oil‐based polyurethane coatings for anticorrosive applications

AbstractThis work describes the synthesis of a hydroxy‐terminated oligomer for polyurethane preparation (HTO‐PU) from rapeseed oil, salicylic acid and toluene diisocyanate. HTO‐PU was further incorporated with different amounts of multiwalled carbon nanotubes (MWCNTs) to produce HTO‐PU@MWCNT nanocomposites. These nanocomposites were then converted to coatings using mild steel strip as a substrate and allowed to cure at room temperature. Fourier transform infrared and NMR spectroscopic techniques were used for structural elucidation. Surface morphology was determined using scanning electron microscopy and X‐ray photoelectron spectroscopy. Thermal stability (>300 °C) of these coatings was evaluated through thermogravimetric analysis and differential scanning calorimetry. Contact angle values suggest that incorporation of MWCNTs enhanced the hydrophobicity of HTO‐PU coatings. Physicomechanical results reveal that these coatings are highly glossy, scratch resistant and impact resistant possessing good adhesion and excellent pencil hardness. The optimum concentration of MWCNTs was found to be 1.0 wt. %, below and above which the coating performance was observed to deteriorate. The corrosion resistance and barrier properties of these coatings were examined using electrochemical impedance spectroscopy, the results of which suggest excellent corrosion inhibition efficiency of HTO‐PU@MWCNT‐1.0 coatings until 28 days. This study suggests a step towards synthesis of MWCNT‐incorporated green PU coatings for protective applications. © 2022 Society of Industrial Chemistry.

Preparation of multicolor microcapsules and their application in smart color-switching textiles

Spiropyran and spiroxazine photochromics have attracted increasing attention in optical data storage, optical switches, and anti-counterfeiting for decades. To expand the applications of spiropyran and spiroxazine, the durability and multi-color changes of spiropyran and spiroxazine still need to be explored. In this article, based on the subtractive principle of dyes, multi-color spiropyran and spiroxazine microcapsules with uniform particle sizes were prepared by the interfacial polymerization method via using compounds (spiropyran and spiroxazine) of different colors as the core material, and polyurethane as the shell material. Among them, toluene diisocyanate and polyethylene glycol constitute the hard and soft segments of polyurethane, respectively. The color of spiropyran and spiroxazine microcapsules can effectively switch between color and colorless, showing excellent photo fatigue resistance. The average particle size of microcapsules is 2.951 µm, and the particle distribution index value is 0.314, which shows the particle size is small and uniform. The maximum thermal decomposition temperature is 426°C, demonstrating good thermal stability. The hydrophobic photochromic fabric was prepared by coating multi-color spiropyran and spiroxazine microcapsules on cotton knitted fabric and hydrophobic treatment. The hydrophobic photochromic fabric is hydrophobic and stain resistant, and exhibits multi-color dynamic switching and long-lasting use. After 50 cycles of washing, the water contact angle of the fabric remains about 109°, showing its good washing resistance and water repellency. In addition, spiropyran and spiroxazine microcapsules are also applied in template and screen printing to impart rich and dynamic color-changing effects to fabrics, fabricating photochromic fabrics. Photochromic fabrics have potential applications in civilian and military fields.

N-Doped Graphene Quantum Dot Nanoparticle Synthesis of Optical Active Thermal Stable Polyurea Nanocomposites Using Polybutadiene Chain Modification

Geminate thermal stability with optical characteristics is a moving forward achievement in the preparation of polybutadiene-based polyurea nanocomposites. In this regard, nitrogen-doped graphene quantum dots were synthesized from a one-pot hydrothermal reaction of citric acid with urea in an aqueous solution. An in situ polymerization approach was used for the synthesis of polyurea from the reaction of telechelic amine functionalized polybutadiene and toluene diisocyanate (TDI) in the presence of the DBTDL catalyst. Nanocomposites were prepared using 1–3 weight percent of graphene N-quantum dot nanoparticles in the polymer matrix. 1H-NMR and FT-IR spectroscopy techniques elaborated successful synthesis of primary polymer binder, polyurea and nanocomposites. Thermal degradation and characteristics were investigated using the TGA/DTG and DSC methods; lower degradation rates with progressed thermal stabilities as well as proportionate thermal characteristics with wider thermal service range were obtained especially in 3 wt% nanocomposite. Optical behavior information of samples was studied using UV-vis absorption and photoluminescence (PL) spectrometers. EDX, SEM, and AFM techniques confirmed successful nanoparticle and nanocomposite synthesis with improved morphologic and topographic properties.

Facile strategy to fabricate palladium-based nanoarchitectonics as efficient catalytic converters for water treatment

Developing facile strategies for anchoring transition-metal nanoparticles (M-NPs) on support materials to make their easy handling, and nascent technologies to advance their applications towards large scale sustainable catalysis are highly demanding. Herein, one-pot strategy is reported for the in-situ immobilization of palladium nanoparticles (Pd-NPs) on highly porous polyurea (PPU). In this approach, Pd acetate (PdAc) solution in tolylene-2,4-diisocyanate (TDI) was gradually added in H2O/acetone (3/7 wt%) mixture under stirring at ambient conditions, followed by the addition of NaBH4 to get Pd/PPU. The combined outcomes of characterizations of resulting Pd/PPU by NMR, SEM, ICP-OES, XRD, XPS, TEM, and BET techniques revealed the successful immobilization of uniformly dispersed Pd-NPs (dmean = 6.2 nm) on PPU having hierarchically porous morphology with specific surface area of 127.13 m2/g. The hybrid composite, Pd/PPU, was used in packed-bed reactor to evaluate its performance as the continuous flow catalytic converter for several toxic organic and inorganic pollutants, as well as their mixture in aqueous medium with the assistance of suitable reductants. The effects of Pd loading, feed concentrations, and permeation flux on the activity of Pd/PPU are discussed. A remarkable permeation flux of 21,000 Lm−2 h−1 (LMH) with > 99% of pollutant’s reduction efficiency and high stability (no change for 20 h used) of Pd/PPU in packed-bed continuous flow catalytic converter were obtained, far better (>10 times) to compare with reported results (2000 LMH) so far. This work therefore provides facile strategy to get PPU-based Pd, a high-performance catalyst for continuous flow reduction of toxic contaminants from wastewaters.

An Ab Initio Investigation on Relevant Oligomerization Reactions of Toluene Diisocyanate (TDI).

2,4- and 2,6-isomers of toluene diisocyanates (2,4-TDI and 2,6-TDI) are important raw materials in the polyurethane industry. These reactive compounds associate even under ambient conditions to form oligomers, changing the physicochemical properties of the raw material. Kinetically and thermodynamically relevant dimerization reactions were selected based on G3MP2B3 calculations from all possible dimers of phenyl isocyanate using these isocyanates as proxies. As it turned out, only the formation of the diazetidine-2,4-dione ring (11-dimer, uretdione) resulted in a species having an exothermic enthalpy of formation (−30.4 kJ/mol at 298.15 K). The oxazetidin-2-one ring product (1-2-dimer) had a slightly endothermic standard enthalpy of formation (37.2 kJ/mol at 298.15 K). The mechanism of the relevant cyclodimerization reactions was investigated further for 2,4-TDI and 2,6-TDI species using G3MP2B3 and SMD solvent model for diazetidine as well as oxazetidin-2-one ring formation. The formation of the uretdione ring structures, from the 2,4-TDI dimer with both NCO groups in the meta position for each phenyl ring and one methyl group in the para and one in the meta position, had the lowest-lying transition state (Δ#E0 = 94.4 kJ/mol) in the gas phase. The one- and two-step mechanisms of the TDI cyclotrimerization were also studied based on the quasi-G3MP2B3 (qG3MP2B3) computational protocol. The one-step mechanism had an activation barrier as high as 149.0 kJ/mol, while the relative energies in the two-step mechanism were significantly lower for both transition states in the gas phase (94.7 and 60.5 kJ/mol) and in ODCB (87.0 and 54.0 kJ/mol).

Synthesis and characterization of polyurethane/zinc oxide nanocomposites with improved thermal and mechanical properties

• Polyethylene glycol and toluene 2,4 diisocyanate (TDI) were used to synthesize polyurethane/zinc oxide (PU/ZnO) nanocomposites. • The presence of main functional groups was verified using FTIR spectra, and XRD patterns indicated hexagonal crystalline NPs with an average particle size of 33.8 nm. • TGA graphs revealed that increasing the concentration of ZnO nanoparticles enhanced the thermal stability of ZnO/PU. • With increasing nanofiller concentrations, the magnitude of Young's modulus continuously rose. The study presents the synthesis of polyurethane/zinc oxide (PU/ZnO) nanocomposites from polyethylene glycol (PEG, MW = 8000) and toluene 2,4 diisocyanate (TDI) within a temperature range of 40 to 60 °C. Structural confirmation and particle size of ZnO were carried out through SEM, FTIR spectroscopy and XRD. Structural insight through XRD presented hexagonal crystals with an average diameter of 33.8 nm. While thermal stability was investigated through thermogravimetric analysis (TGA). The PU/ZnO nanocomposite films were prepared in a Teflon petri dish using different percentages of ZnO; 2%, 4%, 6%, 8%, and 10% in stoichiometric amounts. Functional groups analysis was carried out through FTIR, and it showed the addition of ZnO within the polymer matrix. SEM analysis demonstrated that nanoparticles were homogeneously dispersed all over the polymer surface, responsible for the improvement of inherent properties. TGA study confirmed that homogeneously dispersed nanoparticles improved the thermal stability of polyurethane. The results of TGA graphs showed that the thermal stability of PU/ZnO nanocomposites was increased as the concentration of incorporated ZnO nanoparticles increased as compared to pure polyurethane. Mechanical properties of the nanocomposites were also improved in terms of maximum strain and stress at break, young’s modulus and toughness owed to homogenous dispersion and better material properties.

Shoseiryuto Ameliorated TDI-Induced Allergic Rhinitis by Suppressing IL-33 Release from Nasal Epithelial Cells.

Toluene diisocyanate (TDI) is a major cause of occupational asthma and rhinitis. Shoseiryuto (SST) is one of the traditional herbal medicines (Kampo medicine) and has long been used as a natural medicine for allergic diseases such as allergic rhinitis (AR) and asthma. Recent studies have shown that the expression and release of IL-33, which regulates the TH2 cytokine response in epithelial cells, is an important step in developing the inflammatory response of the nasal mucosa. In this study, we investigated whether SST may ameliorate the TDI-induced AR-related symptoms in rats and inhibit IL-33 release from nasal epithelial cells. An AR rat model was generated by sensitization and induction with TDI. SST was administered during the sensitization period. AR-related symptoms in rats were evaluated, and IL-33 release was measured both in vivo and in vitro. SST suppressed symptoms appearing in TDI-induced AR model rats, such as elevated serum histamine and IL-33 levels in nasal lavage fluid (NLF)/serum, which were suppressed by SST administration. TDI-induced IL-33 release from the nasal epithelial cell nuclei was also observed and suppressed in SST-treated rats and cultured nasal epithelial cells. These results suggest that SST ameliorates the symptoms of TDI-induced AR at least partially by inhibiting IL-33 release from nasal epithelial cells.