Amine Systems Research Articles

Synthesis of a phosphorus‑silicone modifier imparting excellent flame retardancy and improved mechanical properties to a rapid cure epoxy

A liquid bi-functional phosphaphenanthrene siloxane molecule that imparts excellent flame-retardancy and improved mechanical properties to an epoxy amine network was identified and synthesized. The modifier was added to a reactive epoxy amine system to create a low viscosity, miscible, flame retardant resin potentially able to be manufactured via high-pressure resin transfer molding (HP-RTM). The additive reduced the viscosity of the epoxy resin system, remained miscible in the epoxy resin after cure producing a transparent network while simultaneously enhancing self-extinguishing flame retardancy, flexural properties and fracture toughness. At a concentration of 25%, the viscosity of the modified resin system prior to cure was very low (less than 100 mPa.s at 80 °C), cured rapidly (less than 8 min at 150 °C), exhibited a Tg over 110 °C, displayed improved flexural strength (13%), modulus (23%) and fracture toughness (23%), increased thermal stability and displayed self-extinguishing behaviour (UL 94 V-0). Examination after combustion revealed a transformation to a porous but stable char layer likely a result of the synergistic effects of the silicon and phosphorus. The results presented here using represent a promising development for next generation modified epoxy resin systems targeted towards rapid manufacturing of composite materials using HP-RTM.

Features of Preparation of Multilayer Ultrathin Coatings from Thermosetting Epoxy Amine Systems by Spin-Coating Technique

The basic factors influencing the quality of thin films prepared by the spin-coating technique from thermosetting stoichiometric epoxy-amine mixtures have been studied. It has been shown that films 2.5–3.0 nm thick are formed on silicon supports from a 0.025 wt % solution of the stoichiometric mixture of epoxy resin and amine in toluene. Multilayer polymer coatings with thickness up to 40 nm have been prepared from successively deposited partially cured epoxy-amine layers. The thickness of these coatings grows linearly with an increase in the number of layers, while their surface energy decreases. The revealed features may be used for creating multilayer polymer coatings, the properties of which vary along the coating thickness.

Antibacterial activity of 2-amino-3-cyanopyridine derivatives

New 2-amino-4-aryl-3-cyanopyridines were obtained by the three-component condensation of arylidenemalononitriles, malononitrile and (di)amine system or acetoacetanilide. Antibacterial activity of all synthesized compounds against the Gram-negative bacteria E. coli and the Gram-positive B. subtilis was tested, the only representative showed a substantial antimicrobial effect.

Molecular Modeling Study of the SO2 Deactivation of an Amine Resin and a Procedure To Avoid SO2 Deactivation Using a Polyethylene Glycol/Tertiary Amine System

Since 2012, the polymeric resin Lewatit R VP OC 1065 has been investigated for removal of CO2 from various process streams and air. The present article focuses on the deactivation mechanism of the resin with SO2 and a work around. This is important for CO2 capture from flue gas of coal-fired power plants and fuel oil. The deactivation of the resin was already experimentally observed in 2013 but thus far not described computationally. Molecular modeling shows that Lewatit R VP OC 1065 is deactivated by irreversible formation of dimeric amine-SO2 charge-transfer complexes which are very stable and resist thermal and chemical desorption. Additional support for this view was found in the work on aminosilica adsorbents for CO2 capture, which are subject to SO2 deactivation also. Therefore, attention was paid to a procedure to avoid SO2 deactivation. Polyethylene glycol (PEG)/tertiary amine systems seem to be very promising. Their reported high SO2/CO2 selectivities, SO2 capacities, and ease of regeneration were computationally confirmed by identifying their mode of action and favorable thermodynamics. As a result, a combination of a PEG/tertiary amine system with Lewatit R VP OC 1065 might be a very attractive candidate two-step process to capture both SO2 and CO2 from flue gas originating from coal-fired power plants and large ships.

Investigation of Interfacial Free Energy of Three-Phase Contact on a Glass Sphere in Case of Cationic-Anionic Surfactant Aqueous Mixtures

The wetting of adsorbed surfactants solids is important for various technological applications in particular for the process of foam flotation. The present work aims at calculating the surface tensions of the three phase interfaces at different surfactant concentrations using the Girifalco and Good method. For this purpose, the surface tension and contact angle vs. surfactant concentration of the test substances amines and sulfonates and their mixture were measured for liquid–air interface. Calculated surface tension of solid–air interface vs. concentration for C10 amine and mixed systems are close to those for the liquid–air surface, but are slightly lower. In the case of mixed systems, the graph has a specific structure similar to that of liquid–air surface dependence. In contrast to the solid–air interface results, the solid–liquid surface tension values are significantly lower. In case of the mixed surfactant systems, C10amine/C10 sulfonate, a synergetic effect on the surface tension is observed. The specific behavior of the mixed systems is interpreted with the emergence of aggregates consisting of the anionic and cationic surfactants. It is shown that in the whole area of concentrations complete wetting does not occur.

An Electrochemically Mediated Amine Regeneration Process with a Mixed Absorbent for Postcombustion CO2 Capture.

Electrochemically mediated amine regeneration (EMAR) was recently developed to avoid the use of thermal means to release CO2 captured from postcombustion flue gas in the benchmark amine process. To address concerns related to the high vapor pressure of ethylenediamine (EDA) as the primary amine used in EMAR, a mixture of EDA and aminoethylethanolamine (AEEA) was investigated. The properties of the mixed amine systems, including the absorption rates, electrolyte pH and conductivity, and CO2 capacity, were evaluated in comparison with those of solely EDA. The mixed amine system had similar properties to that of EDA, indicating no significant changes would be necessary for the future implementation of the EMAR process with mixed amines as opposed to that with just EDA. The electrochemical performance of the mixed amines in terms of the cell voltage, gas desorption rate, electron utilization, and energetics was also investigated. A 50/50 mixture of EDA and AEEA displayed the lowest energetics: ∼10% lower than that of 100% EDA. With this mixture, a continuous EMAR process, in which the absorption column was connected to the electrochemical cell as the desorption stage, was tested over 100 h. The cell voltage was very stable and there was a steady gas output close to theoretical values. The desorbed gas was further analyzed and found to be 100% CO2, confirming no evaporation of the amine. The mixed absorbent composition was also characterized using titration and nuclear magnetic resonance (NMR) spectroscopy, and the results showed no amine degradation. These findings that demonstrate a stable, low vapor pressure absorbent with improved energetics are promising and could be a guideline for the future development of EMAR for CO2 capture from flue gas and other sources.

Comparative Study and Optimization of CO2 Capture and Storage in LNG-fired Power Plant

In the trends of sustainable development and environmental protection, reducing greenhouse gas emissions and utilizing energy sources are feasible solutions. In this study, Aspen HYSYS-based performance simulations for LNG-fired power plants with CO2 capture and storage using cryogenic and amine technologies were conducted to compare and evaluate. LNG cold energy is employed in liquefied CO2 process. Waste heat from exhaust gas of a gas turbine was powered for steam cycle or stripper column. The results showed that the thermal power generation efficiency of the amine system is lower than that of the cryogenic system, however the excessive gasification of LNG in the MEA system is much lower than that of a cryogenic system. The CO2 mass fraction in recovered liquid of the amine system is also higher than the other one. Multi-objective optimization using genetic algorithm (GA) is then carried out providing a set of optimum solution for investors and operators in balance of the excessive gasification of LNG and CO2 recovery rate.

The joint effect of amine and maleimide functional group in aminomaleimide on the curing kinetics and mechanical properties of epoxy resins

A new epoxy curing system, combining amine and maleimide functionality into a single molecule, was introduced to broaden current state of the art as regards epoxy, amine and maleimide systems. Curing agent aminomaleimide was tested in the curing process of several aromatic and aliphatic epoxies. Prepared mixtures in different weight (molar) ratios were investigated by nonisothermal differential scanning calorimetry to study and compare curing kinetics of different epoxies. The apparent activation energy was determined by Kissinger method, while Friedman method accompanied by Malék statistical approach was used in confirming the autocatalytic nature of epoxy curing and additional maleimide polymerization at the excess amount of aminomaleimide. Thermo-mechanical properties were determined by dynamic mechanical analysis and the effect of aminomaleimide curing agent compared to curing agent containing only amino functional groups was evaluated. Aminomaleimide showed improvement in the glass transition temperatures and higher char yields due to the involvement of maleimide moiety in the curing process. In overall, aminomaleimide showed the positive one-molecule joint effect of the amino group, behaving as an accelerator, and maleimide group, a mechanical properties enhancer.

Rapid Model-Based Optimization of a Two-Enzyme System for Continuous Reductive Amination in Flow

Enzymes are increasingly combined into multienzyme systems for cost and productivity benefits. Further advantages can be gained through the use of immobilized enzymes, allowing continuous biotransf...

A new approach to estimate the curing mode of thermosetting polymer films with regard to physical aging and slow chemical processes

AbstractWe propose an original method to determine the temperature and time required for additional curing of physically aged partially cured glass‐shaped systems, based on the example of epoxy amine systems. The approach consists of the plotting of temperature–time–transformation (TTT) diagrams, supplemented with lines, which illustrate the shift in glass transition temperature (Tg) as a result of the processes of physical aging (enthalpy relaxation) and with isoconversion curves. Then we should determine Tg of partially cured and aged sample at a certain temperature. Having known this Tg value, the position of the isoconversion curve at a given point and Tg,∞ as well, we can determine the postcuring time at T = Tg,∞ + 5 K. Thus, the method provides information about the temperatures and the duration of these two consecutive steps. The TTT diagrams are based on experimental results obtained by differential scanning calorimetry in dynamic mode with preliminary heated samples in an external thermostat. The proposed approach based on epoxy amine systems allows the prediction of the optimal curing mode for thermosetting systems to provide the highest degree of cure. Our method is applicable to a wide range of thermosetting polymer systems that complete transition to a glassy state before full conversion is achieved.

Measurement of Mass Transfer Coefficient of CO2–Amine System from Absorption Process

Carbon dioxide (CO2) is one of the main factors for climate change issues. Absorption is the technology to remove CO2 from various industries. The equipment used is the packed column to promote high mass transfer rate and to study the overall mass transfer coefficient (KGav). The KGav is an important parameter for designing and scaling up of packed column. Therefore, the objective of this work is to measure KGav for CO2 absorption into the aqueous solution of monoethanolamine (MEA) in a random-packed column and to investigate effect of parameters on KGav. The parameters are the solvent flow rate from 5.3-15.9 m3/m2h, CO2 initial loading from 0.0-0.2 mole/mole and CO2 content in gas phase from 5-15 %v/v. The results show that KGav increases as the solvent flow rate and solvent concentration increase. The CO2 content in gas phase provides relatively high impact on KGav with an increase in the CO2 content.

On the physico-chemical basis of self-nanosegregation giving magnetically-induced birefringence in dibutyl phosphate/bis(2-ethylhexyl) amine systems

Dibutyl phosphate (DBP)/bis(2-ethylhexyl) amine (BEEA) liquid mixtures can show optical birefringence when exposed to a magnetic field. It has been hypothesized that this is a consequence of self-segregation characterizing these systems giving formation of anisotropic local assemblies which are able to re-orient under magnetic field. In this work, an ab-initio Density Functional Theory computer modeling coupled with synchrotron X-Ray Scattering (XRS) experiments carried out at various BEEA molar ratio (X) and temperatures (10 ≤ T ≤ 60 °C) permitted to highlight the physical origin of this effect: a DBP-to-BEEA proton transfer with formation of an inherently anisotropic DBP-BEEA ion pair constituting the building block of highly structured ionic liquid nanodomains. At non-equimolar compositions (X ≠ 0.5) such ionic liquids domains are dispersed in the component in excess. At X > 0.5 the ionic liquids nanodomains are dispersed in excess of poorly structured BEEA, creating the ideal assumptions for the formation of a two-phase dispersed system, as confirmed by Guinier analysis in the small angle regime of the XRS spectra, explaining the system capability to become birefringent in reaction to external magnetic field.These information can be transferred to other amphiphiles-based mixtures for the piloted design of new magnetic field responsive materials with advanced applications.

Enhanced malic acid production using Aspergillus niger coupled with in situ product recovery

In the present investigation, recovery of malic acid from the fermentation broth was performed by using in situ reactive extraction method employing different combination of amine and solvent systems. Totally six solvent mixtures were tested for toxicity on Aspergillus niger PJR1. Further, effect of solvent mixture concentration on separation of malic acid was investigated. Solvent system consisting of 2 M of trioctylamine in 1-octanol was found to be non-toxic to A. niger PJR1 and resulted in the maximum partition coefficient of 0.75 when the solvent mixture to liquid ratio of 1:2 used. A. niger PJR1 from crude glycerol using in situ reactive batch fermentation resulted in the maximum malic acid titer of 115.67 ± 3.5 g/L with the productivity of 0.53 g/L.h after 216 h. Further, fed batch extractive fermentation with crude glycerol resulted in malic acid titer of 131.48 ± 3.4 g/L with the productivity of 0.45 g/L.h after 288 h. Thus reactive extraction combined with in situ fermentation could become effective method for enhanced malic acid production.

Mechanism and Chemoselectivity of Mn-Catalyzed Intramolecular Nitrene Transfer Reaction: C–H Amination vs. C=C Aziridination

The reactivity, mechanism and chemoselectivity of the Mn-catalyzed intramolecular C–H amination versus C=C aziridination of allylic substrate cis-4-hexenylsulfamate are investigated by BP86 density functional theory computations. Emphasis is placed on the origins of high reactivity and high chemoselectivity of Mn catalysis. The N p orbital character of frontier orbitals, a strong electron-withdrawing porphyrazine ligand and a poor π backbonding of high-valent MnIII metal to N atom lead to high electrophilic reactivity of Mn-nitrene. The calculated energy barrier of C–H amination is 9.9 kcal/mol lower than that of C=C aziridination, which indicates that Mn-based catalysis has an excellent level of chemoselectivity towards C–H amination, well consistent with the experimental the product ratio of amintion-to-aziridination I:A (i.e., (Insertion):(Aziridination)) >20:1. This extraordinary chemoselectivity towards C–H amination originates from the structural features of porphyrazine: a rigid ligand with the big π-conjugated bond. Electron-donating substituents can further increase Mn-catalyzed C–H amination reactivity. The controlling factors found in this work may be considered as design elements for an economical and environmentally friendly C–H amination system with high reactivity and high chemoselectivity.

Molecular Events for an Epoxy–Amine System at a Copper Interface

Epoxy is a class of thermosetting resins and has been widely used as a representative example of structural adhesives. Nevertheless, it remains unclear how the epoxy resin and curing agent are pres...

Sandwich magnetically imprinted immunosensor for electrochemiluminescence ultrasensing diethylstilbestrol based on enhanced luminescence of Ru@SiO2 by CdTe@ZnS quantum dots

A molecularly imprinted magnetic sensor with electroluminescent tags (MIP-ECL sensor) was developed for ultrasensing diethylstilbestrol (DES). A strategy is exploited to enhance ECL emission of the [Ru(bpy)3]2 +-tripropyl amine (TPrA) system by CdTe@ZnS quantum-dots (QDs) through energy transfer. Magnetically molecularly imprinted nanoparticles (MMIPs NPs) based on Fe3O4@SiO2 carriers are artificial, easily reproducible, and could replace easily inactivated first antibodies for capturing more DES molecules. Functionalized bio-conjugates of single antibody-CdTe@ZnS (Ab-CdTe@ZnS) are for the first time loaded on signal labels of Ru(bpy)32 +-doped silica nanocomposites (Ru@SiO2) for signal amplification. The final bio-conjugated signal probes are denoted as Ab-DES/CdTe@ZnS–Ru@SiO2. MMIPs beads that have captured antigens are bio-conjugated with antibody-labeled luminescent probes by specific immunoreactive reaction, and then the luminescent immunocomplex generates ECL signal on the magnetic electrode. The logarithm of ECL intensities depend linearly on the logarithm of DES concentrations in the range from 4.8 × 10− 4 to 36.0 nM with a detection limit of 0.025 pM. This novel assay is much more sensitive than other MIP sensors, and achieves lower cost and more enhanced stability than other immunosensors. The sensor is significantly potential and has been applied to DES detection in actual environment.

Effect of silica fume and rice husk silica in bio-epoxy composites

The plastic industry is having a rising interest in using bio-resin materials and waste materials for high performance applications. This research assesses the effect of two types of silica in the thermo-mechanical properties and curing behavior of bio-based epoxy composites. Bio-silica (B.S.), obtained from rice husk in our laboratories, and silica fume (S.F.), Aerosil 150, have been used for the development of these composites. An aliphatic epoxy resin, based on Sorbitol Glycidyl Ether (GE60), was crosslinked with two polyetheramine hardeners having oxypolyethylene (PEO) and oxypropylene (PPO) repeating units in the backbone, respectively. The bio-based aliphatic epoxy composites were prepared by a solventless procedure and were cured at room temperature. In general, the epoxy amine systems were reinforced with 3 wt% of both silicas (B.S. and S.F.). The degree of silica dispersion, thermo-mechanical properties and curing monitoring of the composites were analyzed by several techniques described in the paper. The thermal stability increased in both filled networks, but a remarkable improvement in the GE60/PEO/3BS system was observed when compared to S.F. composites. Besides, mechanical properties were also enhanced in the SGE/PEO/3BS system, with 25% of improvement in the Young Modulus and Tensile Strength respect to the other systems. However, the S.F. composites showed a more significant percentage of epoxy conversion when compared with epoxy-biosilica networks. The higher hydrophilicity of PEO was relevant in terms of B.S. dispersion, kinetic reactions, and thermo-mechanical performance.

Highly Efficient Hydrogen Generation from a Formic Acid/Triethanolamine System Using a Pd-Based Catalyst and Correlation for Apparent Activation Energy Estimation

In this study, formic acid (FA)–amine mixtures are investigated as a new hybrid dehydrogenation system over a Pd/sepiolite catalyst synthesized via the efficient impregnation method with an initial turnover frequency of up to 1719 h–1 at room temperature. The characterization results and gas evolution results demonstrate the strong synergistic effect between amine molecules and amine-modified sepiolite. The dissociation constant and oil/water distribution coefficient of the monoamine can directly determine the promoting performance of an amine. In addition, the apparent activation energy of the FA–amine system is much lower than that of the amine-free system. Kinetics correlations of apparent activation energy for the prediction of the monoamine promoting performance were developed and the ability to make accurate predictions was demonstrated, with an average absolute deviation of 1.15%. The equation holds great significance for facilitating the application of amines as they are a clean and low-cost additive.

Stereoselective Syntheses of 3'-Hydroxyamino- and 3'-Methoxyamino-2',3'-Dideoxynucleosides.

Aminonucleosides are used as key motifs in medicinal and bioconjugate chemistry; however, existing strategies toward 3′-hypernucleophilic amine systems do not readily deliver deoxyribo-configured products. We report diastereoselective syntheses of deoxyribo- and deoxyxylo-configured 3′-hydroxyamino- and 3′-methoxyamino-nucelosides from 3′-imine intermediates. The presence or absence of the 5′-hydroxyl-group protection dictates facial selectivity via inter- or intramolecular delivery of hydride from BH3 (borane). Protecting group screening gave one access to previously unknown 3′-methoxyamino-deoxyguanosine derivatives.

A switchable ionic liquid with polarity swing‐assisted regeneration properties used for the preconcentration of cadmium in biological samples

In the present study the cadmium (Cd) was determined in serum samples of psoriatic patients. The severity of psoriasis was evaluated according to criteria based on standard clinical diagnosis using Psoriasis Area Severity Index (PASI) score. In present study, an innovative tunable green solvent system based microextraction (TSS‐ME) was applied for the enrichment of Cd in acid digested serum samples prior to determination with flame atomic absorption spectrometry. The hydrophobic complex of Cd‐ammonium pyrrolidine thiocarbamate was extracted in a tunable solvent system which was prepared from a polybasic amine (N, N, N′, N′‐tetramethyl‐1, 4‐diaminobutane), decanol and water system. The tunable green solvent system (TSS) which has zero ionic strength was converted to homogeneous monophasic polar hydrophilic phase via exposure to CO2 at different pressure and time duration. Then hydrophobic enriched Cd‐ ammonium pyrrolidine thiocarbamate was back extracted, using HNO3 (0.1 to 0.5 mol L−1) then the second round of TSS‐ME was applied. The acidic aqueous phase enrich with analyte was separated from tunable solvent. The separated TSS was easily reused for up to 10 time for preconcentration purposes without loss of its enrichment character. The smoker and nonsmoker psoriatic patients at PASI >10, have two to three folds higher Cd levels in serum samples than healthy persons.