Hexamethylenediamine Research Articles

Mimosa tannin based NIPU wood adhesive with significant substitution of hexamethylenediamine using polyethyleneimine

Tannin-based non-isocyanate polyurethane (NIPU) adhesive exhibits an excellent performance for wood bonding, but contains excess toxic hexamethylenediamine (HMDA), which is emitted to the environment during the preparation of wood panels. Herein, branched polyethylenimine (PEI)/tannin mixtures were utilized to share this adhesive in one integral formulation via various additions at the expense of HMDA. The physical properties, including pH, non-volatile content, viscosity, tannin- and bio-sourced-contents were investigated and compared to a traditional NIPU. The results have shown that the viscosities of the modified adhesives were increased significantly, with improvements at about 2–5% of bio-sourced content and around 4–8% of tannin content being achieved. Moreover, the HMDA content was decreased from 31 % for control T-NIPU-0-0 adhesive to 19 % for the modified adhesives. Possible undergoing reactions of the tannin-NIPU based adhesives series was investigated by Fourier transform infrared spectroscopy (FT-IR) and 13C nuclear magnetic resonance (NMR) analyses. The main tannin-based NIPU structure was maintained even after tannin/PEI mixtures were added. Thermomechanical analysis (TMA) results showed two typical curing stages for either the control adhesive (T-NIPU-0-0) or the modified ones, but different curing performance was observed for modified adhesives, particularly at the first stage. The thermal stability of the modified adhesives was enhanced due to the inserted tannin/PEI mixture, which was proven by thermogravimetric analysis (TGA). The mechanical properties indicated that formulations with suitable weight ratios of tannin/PEI mixtures, such as T-NIPU-4-1 and T-NIPU-5-1 adhesives, could hold a similar performance to the control T-NIPU-0-0 adhesive, which satisfied the European Norm EN 312–2010 for 12- mm boards of type P2. Moreover, a small addition of glycerol diglycidyl ether (GDE) into the T-NIPU-4-1 adhesive endowed an acceptable bonding performance while undergoing different preparation conditions. Therefore, the modified adhesives with the branched PEI/tannin adduct inherited outstanding bonding performance compared to classical tannin-NIPU adhesives along with a noteworthy decreased release of harmful substances such as HMDA, which is in line with the requirements for a cleaner production process.

Alkali-free hydrogenation of adiponitrile to hexamethylenediamine by Co@C skeleton strengthened with carbon nanotubes

Catalytic hydrogenation of adiponitrile to hexamethylenediamine (HMDA) via alkali-free processes is essential to produce high-value downstream chemicals. In this work, we synthesized a series of Co@CCNTx catalysts using CNT promotion to strength the carbon skeleton derived by ZIF-67. Compared to the Co@C without CNT promotion, great enhancement of HMDA yield was achieved by Co@CCNTx. Characterizations suggested that CNT in the precursor modified the crystallization of the active Co centers as well as the surface composition in the Co@CCNTx. Strong Co-carbon interaction was formed via Co-N coordination caused by the facilitated re-dispersion of N- containing functionalities. The ethanol contact angle on Co@CCNTx was changed for better mass transfer and diffusion of reaction liquid on the catalyst. As a final result, the oxidation of cobalt sites was greatly suppressed in Co@CCNT0.3 and Co@CCNT0.5, which was proved an essential factor for their fast reaction rates. 88 % yield of HMDA with the rate of 4.5 molHMDA/molCo/h was reached under a much higher utilization rate of Co center.

Liquid Phase Deposition of TiO2 on a Multifunctional Template of Grafted Gallic Acid and Hexamethylenediamine (GAHD) with Enhanced Electrochemical Properties

Liquid phase deposition is a cost-effective and energy-efficient method for obtaining TiO2 films at low temperatures. This work demonstrates the use of a multifunctional template consisting of grafted gallic acid (GA) and hexamethylenediamine (HD) on a Ti substrate to regulate the deposition of TiO2 films. X-ray diffraction characterization shows that films deposited with the template have a more obvious anatase phase compared to direct deposition at 25 °C. The intensity of photoluminescence spectra also shows significant differences at 373.7 nm and 663.3 nm. Furthermore, electrochemical measurements indicate that TiO2 films adjusted by the template have excellent electrochemical conversion properties. This proposed method provides a new simple route for fabricating TiO2 films that are adjusted by GAHD templates, which may have good applications in the fields of semiconductor materials and biological materials.

Kinetics Study of Acid Hydrolysis of Waste Nylon-6,6 using Anionic Surfactant

The depolymerization reaction of nylon-6,6 is carried out by acidic hydrolysis in the presence of various amounts of sodium dodecyl benzene sulfonic acid (SDBS) (0.02 to 0.07 g) surfactant used as a catalyst at 80 °C and at a different time interval (120 to 240 min). The maximum yield was obtained when 0.05 g SDBS was added to the reaction mixture as a catalyst and 180 min. The reaction mixture was neutralized by 5N NaOH, and the hexamethylene diamine obtained was converted into the Dibenzoyl derivative of hexamethylene diamine (DBHMD), which was filtered, dried, and weighed. The yield was found to be 87.14 %. The characterization was done by the melting point determination and FTIR spectra. The information obtained was in accordance with the literature value. This reaction has followed first-order kinetics with a rate constant of reaction 8.31×10-3 min -1. The IR recorded clearly reveals that the product obtained is pure.

Efficient Removal of Resorcinol from Water Using a New Absorbent Based on Amine-Functionalized [Polyglycidyl Methacrylate-Graft-Polyvinyl Chloride] Copolymer: Isotherms, Kinetics and Thermodynamic Studies

Resorcinol has been classified as an organic pollutant that can cause serious health problems and can even lead to death. Resorcinol is present in the wastewater discharged by many industries and thus threatens the normal life of living beings. In the present work a novel material based on polyvinyl chloride (PVC), glycidyl methacrylate (GMA) and hexamethylenediamine (HDA) was prepared and used as an adsorbent for resorcinol removal from water. GMA was grafted onto PVC by an atom transfer radical polymerization (ATRP) using iodinated PVC (PVC-I) as a macroinitiator. Afterward, the resulting PGMA-g-PVC graft copolymer was functionalized by HDA. The removal of resorcinol using the developed material was carried out by the adsorption process; the obtained results showed that the adsorbent had a maximum adsorption capacity of 943.4 mg/g. In addition, the experimental data revealed that the adsorption process was well-fitted by the pseudo-second-order kinetic model, which indicates the dominance of chemisorption in the adsorption process. Moreover, the developed adsorbent showed good selectivity toward resorcinol in comparison with phenolic products like phenol, hydroquinone and bisphenol A. The synthesized copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H NMR), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD).

Polyethyleneimine-cured epoxy-based solvent tolerant nanofiltration membranes

Epoxy-based nanofiltration (NF) membranes have great potential to allow untapped applications such as the treatment of water/solvent mixtures. However, achieving reproducible membrane performance with concurrent high permeances for water/solvent mixtures and high solute rejections remains challenging. Herein, such a solvent-tolerant NF (STNF) membrane with superior performance characteristics is synthesized through optimizing the non-solvent induced phase separation (NIPS) method by simultaneously curing 2 epoxide building blocks (EPON 1009F (20 wt%) and EPON SU-8 (10 wt%)) with hyperbranched polyethylene imine (PEI) in dimethyl sulfoxide (DMSO). As a multifunctional crosslinker, the hyperbranched PEI, compared to the difunctional linear hexane diamine (HDA), increases the synthesis reproducibility, the membrane flexibility and permeability, offering a remarkable water/DMF (80/20) permeance of 5.7 L m-1 h-1 bar-1 and a rejection of rose bengal (1018 g mol−1) of 93.3%. A decreased permeance and rejection was observed when increasing the solvent content in the water/DMF or water/ethanol feed from 0 to 30 wt%, while a change in water permeance occurred before and after water/solvent filtrations. The epoxy-based membrane is also intrinsically stable in many solvents, and is easy to tune and produce, making it an ideal candidate for the purification of solvent-containing wastewaters from e.g., the pharmaceutical and chemical industries.

2-Amino-2-hydroxymethyl-1,3-propanediol for CO2 capture: study on equilibrium, absorption kinetics, catalytic desorption, and amine regeneration

The CO2-capturing performance of a sterically hindered amine, 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), was systematically studied in this work. First, absorption kinetics was investigated using the stirred-cell technique. At T = 308 K, CO2 reacted with AHPD according to a second-order reaction (rate constant = 264 m3/kmol-s), whose activation energy was 33 kJ/mol. Second, the solubility of CO2 in AHPD at 308 K was measured up to 100 kPa CO2 partial pressure. For instance, it was shown that the loading capacity of AHPD (2.5 M) was 0.56 mol/mol, while the equilibrium CO2 partial pressure was 79 kPa. Third, a closed-loop absorber-desorber setup was used to test solvent performance for capturing CO2 from CO2/air mixture (12:88 v/v). The two columns were continuously operated at 313 (absorber) and 383 K (desorber) at 0.1 MPa pressure. Around 75% CO2 was absorbed using 12 wt. % AHPD (or 0.9 M). The value of QReg (regeneration energy) was 6.28 MJ/kg CO2. It was thus evident that AHPD is a credible hindered amine-based solvent. A comparison of its equilibrium, kinetic and regeneration features with 2-amino-2-methyl-1-propanol (AMP) was provided. Finally, three rate promoters–hexamethylene diamine (HMDA), monoethanolamine (MEA) and AMP–were added to AHPD. The performance of HMDA was most promising. In a batch desorption setup, it was shown that alumina catalyst improved desorption of CO2 from loaded AHPD/HMDA mixtures. This work will stimulate further interest in the use of AHPD solutions for CO2 removal.

Synthesis of magnetic nanoparticles coated zirconia using one-pot solvothermal processes as adsorbent for Pb(II) and Cd(II) removal

Indonesia, notably in Central Kalimantan, has the potential for raw zirconia mineral, but it has not been successfully developed as a material that has ecologically friendly, high economic and technical value. The magnetic nanoparticles coated zirconia mineral was synthesized by using one-pot solvothermal processes, and then was used as adsorbent for water and wastewater treatment in adsorption process. Zirconia minerals are turned into composites with magnetic nanoparticles with the addition of hexane diamine to create the composite with amino groups (MH@ZrO2). It was then utilized as adsorbent to adsorb lead and cadmium metal in an artificial solution, and lower the metal content of lead/ (Pb(II)) and cadmium (Cd(II)) in it. The first stage was to determine the equilibrium of contact time (30, 60, 120, 240, and 360 min) of the adsorbent in binding Pb(II) and Cd(II) ions. The variations of pH 3, 5, 7, and 9 in the solution during adsorption were also examined to establish appropriate conditions for the adsorption process. The observations of magnetic nanoparticles composites based on a Scanning Electron Microscopy (SEM) analysis showed that magnetic nanoparticles with the diameter of 30–50 nm were generated on the face of zirconia minerals. X-Ray Diffraction (X-RD) analysis revealed that zirconia minerals treatment lowered the Crystallinity Index by 11.19% and the silica content by 98%. A Fourier Transform Infra-Red (FT-IR) spectrometer showed an adsorption peak of 590 cm−1 for the Fe-O bond on Fe3O4. Meanwhile, the optimum condition for Pb(II) and Cd(II) adsorption with pHe around 7 ± 0.2 for 360 min resulted in an adsorption density of 117.67 mg/g and 24.19 mg/g, respectively. The MH@ZrO2 led to development for high potential adsorbent due to stable material and easy separation, and capable for absorbing Pb(II) and Cd(II) ions from an aqueous solution.

Deposition of Antioxidant and Cytocompatible Caffeic Acid-Based Thin Films onto Ti6Al4V Alloys through Hexamethylenediamine-Mediated Crosslinking.

A promising approach for advanced bone implants is the deposition on titanium surfaces of organic thin films with improved therapeutic performances. Herein, we reported the efficient dip-coating deposition of caffeic acid (CA)-based films on both polished and chemically pre-treated Ti6Al4V alloys by exploiting hexamethylenediamine (HMDA) crosslinking ability. The formation of benzacridine systems, resulting from the interaction of CA with the amino groups of HMDA, as reported in previous studies, was suggested by the yellow/green color of the coatings. The coated surfaces were characterized by means of the Folin-Ciocalteu method, fluorescence microscopy, water contact angle measurements, X-ray photoelectron spectroscopy (XPS), zeta-potential measurements, and Fourier transform infrared spectroscopy, confirming the presence of a uniform coating on the titanium surfaces. The optimal mechanical adhesion of the coating, especially on the chemically pre-treated substrate, was also demonstrated by the tape adhesion test. Interestingly, both films exhibited marked antioxidant properties (2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assays) that persisted over time and were not lost even after prolonged storage of the material. The feature of the coatings in terms of the exposed groups (XPS and zeta potential titration evidence) was apparently dependent on the surface pre-treatment of the titanium substrate. Cytocompatibility, scavenger antioxidant activity, and antibacterial properties of the developed coatings were evaluated. The most promising results were obtained in the case of the chemically pre-treated CA/HMDA-based coated surface that showed good cytocompatibility and high reactive oxygen species' scavenging ability, preventing their intracellular accumulation under pro-inflammatory conditions; moreover, an anti-fouling effect preventing the formation of 3D biofilm-like bacterial aggregates was observed by scanning electron microscopy. These results open new perspectives for the development of innovative titanium surfaces with thin coatings from naturally occurring phenols for bone contact implants.

Ultrathin organic solvent nanofiltration membrane with polydopamine-HKUST-1 interlayer for organic solvent separation

Polydopamine (PDA) and metal-organic skeleton HKUST-1 were co-deposited on the base membrane of hexamethylenediamine (HDA)-crosslinked polyetherimide (PEI) ultrafiltration membrane as the interlayer, and high-throughput organic solvent nanofiltration membrane (OSN) was prepared by interfacial polymerization and solvent activation reaction. The polyamide (PA) layer surface roughness from 28.4 nm in PA/PEI to 78.3 nm in PA/PDA-HKUST-10.6/PEI membrane, reduced the thickness of the separation layer from 79 to 14 nm, and significantly improved the hydrophilic, thermal and mechanical properties. The flux of the PA/PDA-HKUST-10.6/PEI membrane in a 0.1 g/L Congo Red (CR) ethanol solution at 0.6 MPa test pressure reached 21.8 L/(m2·hr) and the rejection of CR was 92.8%. Solvent adsorption test, N, N-dimethylformamide (DMF) immersion experiment, and long-term operation test in ethanol showed that the membranes had high solvent tolerance. The solvent flux test demonstrated that, under the test pressure of 0.6 MPa, the flux of different solvents ranked as follows: methanol (56.9 L/(m2·hr)) > DMF (39.6 L/(m2·hr)) > ethanol (31.2 L/(m2·hr)) > IPA (4.5 L/(m2·hr)) > N-hexane (1.9 L/(m2·hr)). The ability of the membranes to retain dyes in IPA/water dyes solution was also evaluated. The flux of the membrane was 30.4 L/(m2·hr) and the rejection of CR was 91.6% when the IPA concentration reached 50%. This OSN membrane-making strategy is economical, environment-friendly and efficient, and has a great application prospect in organic solvent separation systems.

Characterization of Polyisobutylene Succinic Anhydride (PIBSA) and Its PIBSI Products from the Reaction of PIBSA with Hexamethylene Diamine.

The nature of the end-groups of a PIBSA sample, namely a polyisobutylene (PIB) sample, where each chain is supposedly terminated at one end with a single succinic anhydride group, was characterized through a combination of pyrene excimer fluorescence (PEF), gel permeation chromatography, and simulations. The PIBSA sample was reacted with different molar ratios of hexamethylene diamine to generate PIBSI molecules with succinimide (SI) groups in the corresponding reaction mixtures. The molecular weight distribution (MWD) of the different reaction mixtures was determined by fitting the gel permeation chromatography traces with sums of Gaussians. Comparison of the experimental MWD of the reaction mixtures with those simulated by assuming that the reaction between succinic anhydride and amine occurs through stochastic encounters led to the conclusion that 36 wt% of the PIBSA sample constituted unmaleated PIB chains. Based on this analysis, the PIBSA sample was found to be constituted of 0.50, 0.38, and 0.12 molar fractions of PIB chains that were singly maleated, unmaleated, and doubly maleated, respectively.

Synthesis, structural analysis, DFT and molecular docking studies of N-(6-(((E)-4-methoxybenzylidene)amino)hexyl)-1-(4-methoxyphenyl) methanimine and its hydrate as a possible 2019-nCoV protease inhibitor

N-(6-(((E)-4-methoxybenzylidene) amino) hexyl)-1-(4-methoxyphenyl) methanimine (1) and its hydrate (2) were synthesized by refluxing hexamethylene diamine and anisaldehyde in presence of catalytic amount of H-Beta zeolite in solvent methanol. Resulting imines were characterized by spectroscopic analysis augmented by Single crystal X-ray diffraction. Both compounds crystalize in monoclinic crystal systems with different point groups P 21 and C 2/c. Pair wise aromatic π-CH and CH- π interactions with distance 2.887 and 2.786 Ao and iminic CH- π interactions with the distance of 2.73 Ao are mainly responsible for extending the structure along 3 dimensions. However, hydrated structure exhibited an addition hydrogen bonding with H of water molecules with the distance of 2.030 Ao , also methoxy O is involved in hydrogen bonding interaction with CH with the distance of 2.641 Ao. Probable contact points and most important crystal packing contributions were determined by employing Hirshfeld surface analysis. H…H and C…H contacts are the most important contributors in the Hirshfeld Surface. Electronic and structural characteristics of both compounds has been calculated using B3LYP/6-311G (d,p) theory. In addition, FMO and MEPS analyses were also accomplished for optimized structures. Molecular Docking studies of compound 1 and 2 were carried out with protease enzyme of 2019-nCoV (PDB-ID 7BRO), monohydrate(2) was involved in more favourable interactions hence accounting for greater binding energy (-7.98 kcal/mol) and inhibition constant (12.96 mM) than compound 1 exhibiting inhibition constant of 39.25 mM and binding energy of -6.23 kcal/mol.

Polyamide recycling demonstration project by Asahi Kasei and Microwave Chemical

Asahi Kasei and Microwave Chemical launched a joint demonstration project in April 2023 with the objective of commercializing a chemical recycling process for polyamide 661 (PA66, also called nylon 66) using microwave technology. The process utilizes microwaves to depolymerize2 PA66 and directly obtain the monomers hexamethylenediamine (HMD) and adipic acid (ADA), which is expected to be accomplished at high yield with low energy consumption. The monomers obtained can then be used to manufacture new PA66. In the demonstration, scraps from manufacturing and post-use waste material of PA66 for airbags and automobile parts are depolymerized.

Facile preparation of epoxidized soybean oil-hexanediamine resin for fabrication of pressure-sensitive adhesives

Due to the massive consumption of petroleum-derived resources, it is imperative to develop biomass adhesives to replace traditional petroleum-derived materials. The current work deals with the possibility to undergo crosslinking of epoxidized soybean oil (ESO) using hexanediamine (HDA) via one-pot method to produce a pressure-sensitive adhesive, poly(epoxidized soybean oil)-hexanediamine (PESH). The chain growth reaction between ESO and HAD involved the ester group in ESO be destroyed via aminolysis, as evidenced by Fourier Transform Infrared Spectroscopy (FTIR) and 1H Nuclear Magnetic Resonance (1H NMR). The bonding properties of PESH pressure-sensitive adhesive were studied by rolling ball method, shear strength and 180° peeling. The results revealed that the initial viscosity, adhesion persistence and peeling were significantly improved when the molar ratio of ESO to HDA was 1:3. At the same time, the PESH adhesive exhibited good bonding performance under water, especially with PVC substrates, in which the underwater bonding strength can reach 1043 KPa. In addition, PESH adhesive with high crosslinking degree presented excellent resistivity at high voltage. It can be implied that the addition of HDA can acquire the PSA antifungal action. All the results support that at a molar ratio of ESO to HDA of 1:3, it is easier to produce robust crosslinked network structure with overall upgraded properties. Conclusively, the developed PESH adhesive can provide a good application prospect in packaging and insulating fields.

Study on gas sensitivity of ZnO@NiO loaded functional carbon materials

We carefully design and prepare a kind of functional carbon material AHC (acetylenic acid - hexamethylene diamine - carbon) using alkynyl acid and cyclohexadiene as raw materials, which load on ZnO@NiO to prepare acetone gas sensor. Studies show that the most appropriate amount of AHC on ZnO@NiO is 0.12% and the best working temperature is 200°C. By comparison, ZnO@NiO@AHC sensor for 100 ppm acetone gas has a maximum response value of 49.08, which is twice as high as of ZnO@NiO sensor. The minimum detection limit is 1 ppm. There is an approximate linear relationship between the concentration and the sensitivity in the range of 1–300 ppm.

A potential recyclable catalyst: In situ growth of bimetallic Cu-Ag nanoalloy on the magnetic SiO2/Fe3O4-SiO2-NH2 nanocomposite support using a green approach

In this study, bimetallic Cu-Ag alloy nanoparticles (NPs) are anchored on the surface of magnetic functional SiO2/Fe3O4-SiO2-NH2 nanocomposite support using glucose as a green reducing agent. SiO2/Fe3O4-SiO2-NH2 nanocomposite support is prepared in one-pot via simultaneous co-precipitation of iron salts and alkaline hydrolysis-condensation reaction of tetraethyl orthosilicate (TEOS) in presence of SiO2 sphere. Hexamethylene diamine (HMDA) and cetyltrimethylammonium bromide (CTAB) are used as functional agent and structure directing agent, respectively. Finally, Cu-Ag NPs are formed on the functional nanocomposite support via in-situ green reduction protocol to obtain SiO2/Fe3O4-SiO2-NH2/Cu-Ag nanocatalyst. A comparative study of catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) showed that calcined SiO2/Fe3O4-SiO2-NH2/Cu-Ag nanocatalyst possessed higher reduction kinetics compared to corresponding non-calcined nanocatalyst. Similar enhancement in catalytic property for unsupported bimetallic Cu-Ag NPs is noticed after calcination. The incorporation of magnetic Fe3O4 in the SiO2/SiO2-NH2 support material also considerably enhanced the catalytic property of the nanocatalyst. The reduction reaction favorably followed pseudo-first-order kinetic rate model and the rate constants of non-calcined and calcined SiO2/Fe3O4-SiO2-NH2/Cu-Ag nanocatalysts are 0.0517 and 0.0998 min−1, respectively. The magnetically separable non-calcined SiO2/Fe3O4-SiO2-NH2/Cu-Ag nanocatalyst is recyclable up to five cycles with fairly acceptable conversion.

The immobilization of Sr(ll) and Co(ll) via magnetic easy-separation organophosphonate-hydroxyapatite hybrid nanoparticles

The magnetic Hexamethylene diamine tetramethylene phosphonic acid (HDTMP)-hydroxyapatite nanoparticles (HD-MHAP) were firstly prepared and applied for the immobilization of radioactive Sr2+ (Strontium ion) and Co2+ (Cobalt ion). The molar ratio of organic phosphine in HDTMP to total phosphorus was 10% (10HD-MHAP) and can also be easily separated from aqueous solution. At the equilibrium concentration of Sr2+ and Co2+ (200 mg/L), the adsorption capacity of MHAP and 10HD-MHAP on Co2+ was 28.4 mg/g and 172.3 mg/g, respectively and for Sr2+, the adsorption capacity was 54.9 mg/g and 320.7 mg/g. Additionally, the desorption percentage of Sr2+ (%) and Co2+ (%) was very low, which was 0.66 and 1.61, respectively. This is significant because the irreversible adsorption of HDTMP/Fe3O4/HAP composite for Sr2+ and Co2+ ensures the captured radionuclides will not be released back into the aquatic systems. Moreover, the affinity between HDTMP and HAP and the coordination of HDTMP and Sr2+ or Co2+ was probed by Multiwfn wavefunction analysis. The results indicated that the formation of a ternary surface complex of MHAP-HDTMP-M (Sr2+ or Co2+) was the key to the excellent immobilization performance of HD-MHAP composite for Sr2+ or Co2+.

Study on the determination of some diamine in urine by LC-MS/MS

Isocyanate is a common name for chemical compounds containing one or more - NCO groups. There have been many studies showing that isocyanates pose a risk to human health when exposed and can cause occupational poisoning. When absorbed into the body, the isocyanates will be converted into the corresponding amines. Therefore, the determination of these diamines in urine will contribute to the assessment of exposure to isocyanates. This article presents a study on simultaneous determination of 4,4′-methylenedianiline (MDA), hexamethylene diamine (HDA), isophoron diamine (IPDA) in urine by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method detection limit (MDL) were 0.074, 0.059, and 0.053 ng/mL for HDA, MDA, IPDA, respectively. The method quantitation limit (MQL) were 0.243, 0.194 and 0.177 ng/mL for HDA, MDA, IPDA, respectively. The method's recovery ranged from 86.38 to 105.3% with the repeatability RSDr < 6%. The method was successfully applied to simultaneously determine the content of HDA, MDA and IPDA in 30 urine samples of workers at auto repair garages in Bac Ninh province. The results showed that HDA, MDA and IPDA were detected in these samples with different concentrations.

Tailor-Made Bio-Based Non-Isocyanate Polyurethanes (NIPUs)

Non-isocyanate polyurethanes (NIPUs) based on biobased polyamines and polycarbonates are a sustainable alternative to conventional polyurethanes (PU). This article discloses a novel method to control the crosslinking density of fully biobased isocyanate-free polyurethanes, synthesized from triglycerides carbonated previously in scCO2 and different diamines, such as ethylenediamine (EDA), hexamethylenediamine (HMDA) and PriamineTM-1075 (derived from a dimerized fatty acid). As capping substances, water or bioalcohols are used in such a way that the crosslinking density can be adjusted to suit the requirements of the intended application. An optimization of the NIPU synthesis procedure is firstly carried out, establishing the polymerization kinetics and proposing optimal conditions set for the synthesis of the NIPUs. Then, the influence of the partial blocking of the active polymerization sites of the carbonated soybean oil (CSBO), using monofunctional amines, on the physical properties of the NIPUS is explored. Finally, the synthesis of fully biobased NIPUs with a targeted crosslinking density is achieved using hybrid NIPUs, employing partially carbonated oil and H2O or ethanol as blockers to achieve the desired physical properties in a very precise manner.

Eco-Friendly Tannin-Based Non-Isocyanate Polyurethane Resins for the Modification of Ramie (Boehmeria nivea L.) Fibers.

This study aimed to develop tannin-based non-isocyanate polyurethane (tannin-Bio-NIPU) and tannin-based polyurethane (tannin-Bio-PU) resins for the impregnation of ramie fibers (Boehmeria nivea L.) and investigate their mechanical and thermal properties. The reaction between the tannin extract, dimethyl carbonate, and hexamethylene diamine produced the tannin-Bio-NIPU resin, while the tannin-Bio-PU was made with polymeric diphenylmethane diisocyanate (pMDI). Two types of ramie fiber were used: natural ramie without pre-treatment (RN) and with pre-treatment (RH). They were impregnated in a vacuum chamber with tannin-based Bio-PU resins for 60 min at 25 °C under 50 kPa. The yield of the tannin extract produced was 26.43 ± 1.36%. Fourier-transform infrared (FTIR) spectroscopy showed that both resin types produced urethane (-NCO) groups. The viscosity and cohesion strength of tannin-Bio-NIPU (20.35 mPa·s and 5.08 Pa) were lower than those of tannin-Bio-PU (42.70 mPa·s and 10.67 Pa). The RN fiber type (18.9% residue) was more thermally stable than RH (7.3% residue). The impregnation process with both resins could improve the ramie fibers' thermal stability and mechanical strength. The highest thermal stability was found in RN impregnated with the tannin-Bio-PU resin (30.5% residue). The highest tensile strength was determined in the tannin-Bio-NIPU RN of 451.3 MPa. The tannin-Bio-PU resin gave the highest MOE for both fiber types (RN of 13.5 GPa and RH of 11.7 GPa) compared to the tannin-Bio-NIPU resin.