OH Ratio Research Articles

Interpreting the Seasonality of Atmospheric Methane

AbstractSurface and satellite observations of atmospheric methane show smooth seasonal behavior in the Southern Hemisphere driven by loss from the hydroxyl (OH) radical. However, observations in the Northern Hemisphere show a sharp mid‐summer increase that is asymmetric with the Southern Hemisphere and not captured by the default configuration of the GEOS‐Chem chemical transport model. Using an ensemble of 22 OH model estimates and 24 wetland emission inventories in GEOS‐Chem, we show that the magnitude, latitudinal distribution, and seasonality of Northern Hemisphere wetland emissions are critical for reproducing the observed seasonality of methane in that hemisphere, with the interhemispheric OH ratio playing a lesser role. Reproducing the observed seasonality requires a wetland emission inventory with ∼80 Tg a−1 poleward of 10°N including significant emissions in South Asia, and an August peak in boreal emissions persisting into autumn. In our 24‐member wetland emission ensemble, only the LPJ‐wsl MERRA‐2 inventory has these attributes.

Waterborne 2-component polyurethane coatings based on acrylic polyols with secondary alcohols

We report the effects of increasing the molecular weight of a secondary alcohol-based polyol in a two-component waterborne polyurethane (2 K-WB-PUR) formulation. The system consists of an acrylic polyol latex and a water-dispersible polyisocyanate (hmPIC, Basonat HW1000 from BASF). The polyols investigated incorporated hydroxypropyl methacrylate as a comonomer to introduce the secondary –OH groups, in contrast to typical polyols which have primary -OH groups. Three molecular weights of this polyol were prepared (Mn ≈ 5100, Ð = 2.4; 10,300, Ð = 2.7; or 12,900 g/mol, Ð = 3.6) with a uniform Tg (∼20 °C) and hydrodynamic diameter (dh) ≈ 120 nm. The polyol and polyisocyanate were mixed with a molar NCO:OH ratio of 1.3:1. The particle size of the mixed dispersion was monitored by dynamic light scattering. The 5 K sample remained stable in dispersion over 7 days whereas the higher molecular weight formulations flocculated after 1 day. Fourier Transform Infrared (FTIR) measurements revealed that all NCO groups were consumed within 15–23 h for all dispersed samples. Fluorescence resonance energy transfer (FRET) experiments were carried out on samples in the dispersed state as well as on films formed from these dispersions. Very little molecular level mixing was observed in the dispersed phase for the samples. In the films, a large extent of mixing was observed in the 5 K sample whereas the extents of mixing for the higher molecular weight samples were reduced. The FTIR measurements recorded as the films formed showed that the NCO consumption in the 5 K film (t1/2 = 56 h) was comparable to an analogous 2 K-WB-PUR formulation based on a 5 K primary alcohol from a previous study. Surprisingly, the NCO consumption in the higher molecular weight samples was faster (t1/2 = 31, 32 h). We found that the composition of the resulting films formed from higher molecular weight polyols contained a greater relative ratio of polyurea to polyurethane.

Tough hyperbranched polyaryletherketone-based photosensitive resins bearing excellent dielectric property and thermal resistence

Organic polymer materials with low dielectric properties have garnered significant attention due to their convenient preparation process, low cost, and commendable mechanical properties. Such polymers, especially with heteromorphic structures, exhibited great potential for future electronic devices and antennas, particularly accompanied with rapid manufacturing technologies like three-dimensional (3D) printing. In this study, a series of new allyl ether-ended hyperbranched fluorene-based polyaryletherketone (hb-PFAEK-Allyls) were developed. The content of allyl ether photosensitive groups and molecular weight were controlled by adjusting the molar ratio of OH:F loading. UV-curable resins were then prepared through blending between hb-PFAEK-Allyls with trimethylolpropane triacrylate (TMPTA) and ethylene glycol bis(3-mercaptopropionate) (EGBMP), resulting in thiol-allyl-acrylate ternary UV-cured system. The influence of molecular weight of the hyperbranched polymers on the thermal performance, mechanical properties, and dielectric properties of the UV-cured films was systematically investigated. The results show that due to the introduction of hyperbranched structure with high molecular weight, the Tg of the UV-cured film can reach up to 248 °C. Due to the increased molecular free volume in the hyperbranched structure, the dielectric constant of the UV-cured film can be reduced to as low as 2.74 at 1 GHz. Due to the design of thiol-allyl-acrylate ternary UV-cured system, the cured film has excellent mechanical properties, with the highest tensile strength of 61.0 MPa and the elongation at break of 7.0%. This study represents innovative progress on integrating fully aromatic-based photosensitive hyperbranched polyaryletherketone into UV-curable resin architecture. Overall, the herein hb-PFAEK-Allyls-based photosensitive resins exhibit outstanding comprehensive performance and holds great potential for application in advanced 3D printing technology.

Key to unlocking NO2 sensing performance of monolayer Ti3C2Tx: Regulating OH/F functional groups

A surface functional group modulation method was used to regulate the NO2 sensing performance of the Ti3C2Tx sensor. The monolayer Ti3C2Tx MXene was synthesized from Ti3AlC2 (MAX phase) by hydrofluoric acid (HF) etching. Ar/O2 hybrid plasma treatment was used to regulate the ratio of hydroxyl and fluorine functional groups (OH/ F) in the Ti3C2Tx surface structure. Room-temperature (RH) NO2 sensor based on modified Ti3C2Tx was fabricated by the dip coating method. The modified Ti3C2Tx sensor has a higher gas response (45.31 %) to 50 ppm NO2 compared with the untreated Ti3C2Tx sensor which shows more excellent sensitivity and linearity with the NO2 concentration of 5–50 ppm. It is due to that the presence of the hydroxyl potential on the Ti3C2Tx surface well amplifies the electronic surface activity of Ti3C2Tx. Concurrently, the modified electronic structure augments the adsorption propensity of Ti3C2Tx for O2 (2.26 |eV|) and NO2 (3.24 |eV|), thereby improving the NO2 sensing capability of the Ti3C2Tx sensor. These results demonstrate that Ti3C2Tx with a high ratio of OH/ F functional groups has great potential in developing high-performance room temperature NO2 sensors.

Antimicrobial Activity of Morphology-Controlled Cu2O Nanoparticles: Oxidation Stability under Humid and Thermal Conditions.

Metal oxides can be used as antimicrobial agents, especially since they can be fabricated into various forms such as films, masks, and filters. In particular, the durability of antimicrobial agents and the duration of their antimicrobial activity are important factors that determine their suitability for a specific purpose. These factors are related to the morphology and size of particles. The metal oxide Cu2O is often oxidized to CuO in various conditions, which reduces its antimicrobial activity. This study focused on the oxidation of nanoparticles of Cu2O with three morphologies, namely, spherical, octahedral, and cubic morphologies, in excessively humid and excessive-thermal environments for a specific duration and the antimicrobial activity of the NPs. Cu2O nanoparticles were prepared using the chemical reduction method, and their morphology could be varied by adjusting the molar ratio of OH- to Cu2+ and changing the reducing agent. It was found that cubic Cu2O was the most stable against oxidation and had the smallest reduction in antimicrobial activity. This study examined the antimicrobial activity and the oxidation stability of Cu2O NPs with different morphologies but similar particle sizes.

Water release from dacitic melts near the glass transition and implications for volcanic eruptions

To get insights in the mechanisms of magma degassing and fragmentation, we performed dehydration experiments at ambient pressure with dacitic glasses containing between 1.42 and 5.28 wt% H2O. The focus was on the degassing behavior in the range of glass transition, i.e., from temperatures 50 K below to 50 K above the glass transition temperature Tg. At each T the duration of the experiments was varied between 5 and 125 h. Water contents and initial water speciation was determined by FTIR spectroscopy. Diffusion depth profiles were measured by Raman spectroscopy. We developed an equation to calculate the total water content along the depth profiles from the ratio of the fundamental OH stretching vibration band at 3550 cm−1 and the T-O-T bending band near 500 cm−1. Glasses with high water content (4.66–5.28 wt%) showed huge alterations, i.e., crack formation below Tg and crystallization at and above Tg, but glasses with water contents up to 2.5 wt% were visually unchanged and suitable for water diffusion analysis.The measured profiles of total water content vs. distance can be fitted well by an error function, assuming that the water content in the glass does not decrease to zero at the surface. However, the apparent water concentration at the surface and the total water diffusivity derived from the error function fitting decrease with increasing duration of the experiment. This clearly shows that degassing of dacitic melts is not a simple out-diffusion mechanism. The model of Coumans et al. (2020) that explicitly considers the kinetics of the interconversion of water species can reproduce the temporal evolution of the total water concentration profiles very well. Our results show the importance of considering explicitly the interconversion kinetics of water species when modelling water diffusion in melts at high viscosities. Due to the slow interconversion of OH groups to much more mobile water molecules, dehydration is much slower in the range of glass transition than predicted by diffusion models based on experiments performed on stable melts at magmatic temperatures.

Effect of mixed surface terminations on the work function and quantum capacitance of Sc2CT2 monolayer

MXenes are two-dimensional transition metal carbides and nitrides, which are promising for supercapacitor applications. The surface of MXenes is usually covered by a mixture of O, OH, and F groups during etching. The effect of mixed termination on the quantum capacitance and work function (WF) of MXenes is investigated by first principles calculation. The WFs of Sc2C(OH)2-R are smaller than those of Sc2CO2-R and Sc2CF2-R when the OH ratio is larger than about 27 %. The quantum capacitances of Sc2C MXenes with different ratio of F, O, and OH groups (named as Sc2CF2-R, Sc2CO2-R, Sc2C(OH)2-R) are explored to predict the electrode type of materials. Negative binding energies confirm the stability of the studied mixed systems. The increasing ratio of O group can make the system have decreased TDOS near Fermi level, thus decreasing quantum capacitance. The top quantum capacitance of Sc2CO2-R and Sc2C(OH)2-R systems at negative bias increase with the increasing ratio of O/OH group. All systems have larger storage charge at negative potential, and are all potential cathode materials, especially for Sc2CO2-R and Sc2CF2-R MXene with much smaller |Qa|/|Qc| than 1 and larger Cc. The quantum capacitance under wide voltage is also considered.

Kinetic research on ion exchange regeneration of quaternary ammonium-based CO2 sorbent for direct air capture

To satisfy the Paris Agreement's 1.5 °C goals, direct air capture (DAC) has become an increasingly crucial technology. However, the ultralow partial pressure of CO2 in ambient air contributes to a low desorption rate and high regeneration energy consumption. In this study, we proposed a fast regeneration method for CO2 sorbents based on an ion exchange process. Utilizing an alkaline solution rich in hydroxide (OH–) ions, the quaternary ammonium (QA)-based ion exchange resin can be changed from carbonate (CO32–) to OH– form, which directly captures CO2 from ambient air. The results showed that the working capacity of the sorbents in the OH– form was 1.85 mmol⋅g−1, which was double that of the CO32– form (0.88 mmol⋅g−1). The kinetics showed that the ratio of OH–/HCO3– at inlet, concentration, and external diffusion influence the desorption rate of CO32– because of the ion exchange reaction. With a high ratio of OH–/HCO3– at inlet, 1 M alkaline solution, and 3 mL⋅s−1 cyclic flow rate, the desorption time of the sorbents was approximately 20 min. Finally, because the energy consumption of the entire process comprises mainly electric energy required to regenerate the alkaline solution after ion exchange, it is expected to establish an electrochemical DAC system to utilize renewable energy efficiently.

Synthesis of hydroxyl silane coupling agent and its application in preparation of silane‐modified polyurethane

AbstractThis study describes the synthesis of a hydroxyl silane coupling agent (HO‐silane) through a click reaction between SH in 3‐(trimethoxysilyl)propane‐1‐thiol (KH‐590) and CC in 2‐hydroxyethyl methacrylate (HEMA). This coupling agent was subsequently employed in the synthesis of silane‐modified polyurethane (SPU) resin which could be moisture‐cured at room temperature. The influence of r values (the molar ratio of NCO and OH) on the characteristics of SPU resins was investigated. These results reveal that an increase in the r value leads to a reduction in viscosity from 4.9 × 105 to 1.9 × 105 mPa·s, a rise in tensile strength from 0.88 to 0.98 Mpa followed by a decline to 0.69 MPa, and a reduction in extension at fracture from 236% to 94%. A SPU resin with a viscosity of approximately 3.6 × 105 mPa·s, tensile strength of 0.98 MPa, and elongation at break of 218% can be produced when the r value is 1.8. In addition, a silane‐modified polyurethane (MS) sealant with a tensile strength of 1.6 MPa in addition to elongation at break at 336% could be produced using the aforementioned SPU resin.

Preparation of Ca(OH)2 nanoparticles by impinging stream reaction precipitation method

AbstractIn this paper, Ca(OH)2 nanoparticles are prepared by impinging stream co‐precipitation method. The process of preparing nanoparticles by impinging stream is optimized. The influence of process variable, such as dispersant type, dispersant dosage, circulating flow rate, reactant concentration ratio of OH− and Ca2+, reaction temperature and circulation time, on the particle size of Ca(OH)2 nanoparticle are investigated. The results show that the concentration ratio of reactants has a significant effect on the size of Ca(OH)2 nanoparticles. The optimal process conditions are obtained by single factor experiment, PEG6000, 3.3% dispersant dosage, Q = 1000 L · h−1, C = 1.88, T = 46.68°C and t = 60 min. The average particle size of Ca(OH)2 nanoparticles prepared under these conditions is 107.67 nm. According to the microstructure analysis, the prepared Ca(OH)2 nanoparticles samples have high purity and a good crystal structure. The powder dispersed with a marked hexagonal crystal shape and good thermal decomposition.

Does Water Play a Crucial Role in the Growth of ZnO Nanoclusters in ZnO/Cu Catalyst?

The catalytically active configuration of ZnO/Cu in the commercial ZnO/Cu/Al2O3 catalyst for methanol synthesis from CO2 is still not clear. In this study, we employ density functional theory based methods to shed light on the structure and stoichiometry of ZnO clusters both free in the gas phase and also deposited on the Cu(111) surface under methanol synthesis conditions. Specifically, we investigate the structural evolution of ZnO clusters in the presence of hydrogen and water. We find that the stability of ZnO clusters increases with the concentration of water until the ratio of Zn and OH in the clusters reaches 1:2, with a morphological transition from planar to 3D configurations for clusters containing more than 4 Zn atoms. These clusters exhibit weak interaction with CO2, and water is predicted to block the active center. The Cu(111) surface plays an important role in enhancing the adsorption of CO2 on the ZnO/Cu(111) systems. We infer that ZnO nanostructures covered with OH species may be the morphology of the ZnO during the methanol synthesis from the hydrogenation of CO2 on the industrial catalyst.

Steric hindrance affects interactions of poly(styrene–alt–DMHPMI) copolymer with strongly hydrogen-bond-accepting homopolymers

In this study, we synthesized the monomer N-(2,6-dimethylhydroxyphenyl)maleimide (DMHPMI) in three steps from 2,6-dimethylphenol and then reacted it with styrene through free radical copolymerization to prepare the alternating copolymer poly(styrene–alt–dimethylhydroxyphenylmaleimide) [poly(S–alt–DMHPMI)]. We used Fourier transform infrared (FTIR) spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and mass-analyzed laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry to confirm its structure. Differential scanning calorimetry revealed that blends of the alternating copolymers poly(S–alt–DMHPMI) and poly(styrene–alt–(para–hydroxyphenylmaleimide)) [poly(S–alt–pHPMI)] with the Strongly Hydrogen-Bond-Accepting homopolymers poly(4-vinylpyridine) (P4VP) and polyvinylpyrrolidone (PVP) each exhibited single-value glass transition temperatures (Tg) over the entire compositional range, indicative of full miscibility. Nevertheless, a negative deviation from the linear rule occurred for the Tg behavior of the PS–alt–PHPMI/P4VP blends, due to the weak acidity of the HPMI units, while the intermolecular interactions of the PS–alt–PHPMI coplymers were also inhibited because of strong self-association of the PHPMI units. FTIR spectral analyses of the ratio of hydrogen-bonded OH and pyridyl groups confirmed this behavior. In contrast, slightly positive deviations from the linear rule occurred for the Tg behavior when blending poly(S–alt–DMHPMI) or poly(S–alt–pHPMI) with the PVP homopolymer; here, the intermolecular interactions of the poly(S–alt–DMHPMI)/PVP blends were weaker than those of the poly(S–alt–pHPMI)/PVP blends, due to the steric hindrance of the DMHPMI units being greater than that of the pHPMI units.

Understanding the electro-cocatalytic peroxymonosulfate-based systems with BDD versus DSA anodes: Radical versus nonradical dominated degradation mechanisms

Herein, peroxymonosulfate (PMS) activation via electro-cocatalytic system with circulated Fe(III)/Fe(II) was investigated with boron-doped diamond (BDD) anode and dimensionally stable anode (DSA) for degradation of sulfamethoxazole (SMX). Radicals of OH and SO4− as well as non-radicals of 1O2 and Fe(IV) were all present in BDD/PMS/Fe(III) and DSA/PMS/Fe(III) systems, according to the results of scavenging experiment and electron paramagnetic resonance (EPR) analysis. Interestingly based on the results of chemical probe experiments, the ratio of OH, SO4−, and 1O2 were 9% (7.19 μmol/L), 76% (58.39 μmol/L), and 15% (11.45 μmol/L) in BDD/PMS/Fe(III) system, and were 28% (5.81 μmol/L), 18% (3.76 μmol/L), and 54% (10.93 μmol/L) in DSA/PMS/Fe(III) system. The yield of Fe(IV) in DSA/PMS/Fe(III) process was relatively higher than that in BDD/PMS/Fe(III) process. These results indicated that BDD/PMS/Fe(III) is a radical oxidation system while DSA/PMS/Fe(III) system is mainly non-radical system. Due to the high electrochemical activity of BDD anode, the one-electron transfer reaction might occur to produce more SO4−. The co-existing ions including Cl−, H2PO4−, and NO3− showed significant effects on the degradation efficiency of BDD/PMS/Fe(III) and nonsignificant impacts on DSA/PMS/Fe(III) process, indicating that DSA/PMS/Fe(III) process could be less affected by complex water matrix. BDD/PMS/Fe(III) is inclined to oxidize electron-rich contaminants, while DSA/PMS/Fe(III) is apt to oxidize electron-deficient contaminants. The degradation routes of SMX and its toxicity evolution were systematically studied with the analysis of byproducts. Overall results compared the oxidation mechanisms and primary oxidation pathways of electro-cocatalytic systems with BDD versus DSA anodes, and revealed the merits of each system for future selection and system optimization of treatment processes regarding targeted contaminants.

Synthesis of Alkyd Resin Through Alcoholysis – Polyesterification Process from Used Cooking Oil Pretreatment Using Alkaline Activated Natural Bayah Zeolite

Waste cooking oil can be treated by an adsorption process using Bayah natural zeolite as raw material for alkyd resin synthesis. This study aimed to determine the optimum conditions for the equivalent ratio of OH:COOH and the temperature of the alkyd resin synthesis. The research was carried out by preparing used cooking oil and Bayah natural zeolite (BNZ), adsorption process, and alkyd resin synthesis through the alcoholysis-polyesterification process. The optimum addition of Bayah natural zeolite-activated NaOH 0.75 N in pretreatment waste cooking oil is 30% weight in terms of color, density, viscosity, and functional group characteristics of the resulting alkyd resin. The characteristics of the alkyd resin product at optimum conditions obtained light brown color with an OH: COOH equivalent ratio of 1.4, and the alcoholysis and esterification temperature at 190 oC with a density value is 1.112 g/cm3, FFA value is 0.1528%, viscosity value is 4808 cP. The ester functional group at wavelengths 1267 cm-1 and 1722 cm-1, the 1H NMR spectrum of the ester group at the peak of 3.5 ppm, and a functional group of 7.6 ppm.

Dissolution mechanisms of water in depolymerized silicate (peridotitic) glasses based on infrared spectroscopy

The dissolution of water changes the chemical and physical properties of melts. The effect of water dissolution depends on the bulk H2O content and dissolution mechanisms. Previous research mainly focused on relatively polymerized glasses, whereas dissolution mechanisms of water in highly depolymerized glasses have not been well studied. We investigated three sets of hydrous (up to 5 wt% H2O), highly depolymerized glasses using Fourier transform infrared spectroscopy. The three suites of glasses can be classified as tephritic (non-bridging oxygens to tetrahedral cations, NBO/T ≈ 0.9), basanitic (NBO/T ≈ 1.5), and peridotitic (NBO/T ≈ 2.5). The comparison of infrared spectra indicated four prominent features. First, the combination band related to molecular H2O at ∼ 5200 cm−1 decreases in relative intensity with increasing depolymerization. At 2 wt% bulk H2O, the proportion of H2O molecules decreases from the tephritic through basanitic to peridotitic glasses, where the proportion of H2O molecules is below 10 %. At 5 wt% bulk H2O, the proportion of H2O molecules in the peridotitic glass is around 20 %, whereas it is around 50 % in the basaltic glass with the same H2O content. Second, a second peak appears at 4270–4180 cm−1, next to the (Si,Al)OH combination peak (network hydroxyl), with increasing CaO and MgO contents in basanitic (∼25 wt% CaO) and peridotitic (∼40 wt% MgO) glasses, respectively. We assign this peak to the (Mg,Ca)OH group (free hydroxyl); this is the first identification of this group based on infrared spectroscopy. This assignment is also supported by IR data on Mg(OH)2 and Ca(OH)2 crystalline phases from the literature. Third, the ratio of (Si,Al)OH and (Mg,Ca)OH peak absorbances remains nearly constant with increasing water content in basanitic and peridotitic glasses, suggesting no effect of water on polymerization of extremely depolymerized melts. Fourth, the (Si,Al)OH peak shifts to lower wavenumbers with increasing depolymerization. As a result, the (Si,Al)OH peak position could potentially be used to evaluate the degree of melt polymerization in general, and the effect of water on melt polymerization in particular.

Microwave-assisted controllable synthesis of 2D and 1D Eu3+-Y2O3 micro/nanoparticles and their photoluminescence properties

Rare earth elements doped yttria is a group of important functional materials used in various applications. In this work, Eu3+-Y2O3 particles with different morphology including nanoplates, porous nanoplates, quasi-triangular microprisms, hexagonal microprisms, microcylinders and nanorods have been synthesized by a facile two-step method without using any template or surfactant. The mixture of Eu(NO3)3, Y(NO3)3 and NaOH solution were irritated by microwave for 10 ​min to form the intermediate hybrid precursors, and the final Eu3+-Y2O3 were obtained by calcining the intermediate powder at 600 ​°C for 3 ​h. The morphologies, microstructure, crystal phase and composition of the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermal analysis (TG–DSC) in detail. The results show that the shapes can be controlled effectively from two dimension (2D) to one dimension (1D), and the size can be adjusted from microscale to nanoscale by changing the ratio of OH−/Re3+ only. The photoluminescence (PL) intensity and decay time of the particles vary significantly with the morphologies.

A comprehensive investigation of zeolite-rich tuff functionalized with 3-mercaptopropionic acid intercalated green rust for the efficient removal of HgII and CrVI in a binary system

In this study, the 3-mercaptopropionic acid (MA) was chosen to achieve the anionic intercalation into the green rust (GR) materials (MA-GR). The zeolite-rich tuff functionalized with the MA-intercalated GR (MA-GR-tuff) was subsequently synthesized and used to remove both HgII cations and CrVI anions in a binary system. MA-GR-tuff showed the best adsorption capacities to both HgII and CrVI among the adsorbent materials. The optimal combination of parameters was determined as the molar ratio of FeII to FeIII of 3.5, the molar ratio of OH− to the total iron of 3.75, the molar ratio of MA to the total iron of 2.5, and the mass ratio of the total iron to the tuff of 1.25. The pseudo-first-order kinetic model was appropriate in describing the kinetic sorption of CrVI by MA-GR-tuff. Both the pseudo-first-order kinetic model and Elovich were suitable for explaining HgII sorption. The maximum monolayer adsorption capacities of MA-GR-tuff towards CrVI and HgII were 185.19 mg/g and 72.99 mg/g, respectively. More flocs and plumes were formed in the MA-GR while the intercalation and more pores and crevices of different sizes were found in the MA-GR-tuff. Sulfhydryl complexation and the molecular sieve of tuff obviously both played a role in influencing the adsorption process. This study directly overcomes the drawback brought by the natural tuff to the treatment of a cationic-and-anionic binary system and supplies a new kind of tuff-based adsorbent for the potential use for the remediation of HM-contaminated wastewater.

Extending the pot life of polyurethane coatings using organic diones

PurposeThis study aims to extend the pot life without altering the qualities and performance of the coating, which is important to increase when manufacturing polyurethane coatings.Design/methodology/approachAn acrylic polyol from a mixture of different monomers of hydroxypropyl methacrylate, methacrylic acid, 2-ethylhexyl acrylate, methyl methacrylate and n-butyl methacrylate was prepared with different ratios of 2,4-pentanedione as a pot life extender. The reaction takes place in presence of di-tert-butyl peroxide as initiator with samples (T1–T7). The physical properties of prepared acrylic polyol were characterized. Then, coating polyurethane varnish was prepared from the prepared acrylic polyol with an aliphatic polyisocyanate in a 1:1 equivalent ratio of OH:NCO at room temperature, in presence of paint thinner (diluents/solvent) and dibutyltin dilaurate as a catalyst to give samples (T1C–T7C). This coating was evaluated via Fourier-transform infrared spectroscopy, drying time, hardness and gloss, distinctness of image and reflected image quality.FindingsThe coating has a prolonged pot life while still maintaining the other qualities, thanks to the greater 2,4-pentanedione content.Originality/valueIt is desired to have a paint which has a satisfactory pot life, short curing time and reduces many drawbacks such as inefficient working and deterioration of the paint before application.

The Laccase-Lig Multienzymatic Multistep System in Lignin Valorization.

A laccase-Lig multienzymatic multistep system for lignin depolymerization was designed and developed. Studies were performed on pristine and fractionated lignins (Kraft and Organosolv) using a specific cascade of enzymes, that is, laccases from Bacillus licheniformis and from Funalia trogii, respectively for Kraft and Organosolv lignin, followed by the Lig system from Sphingobium sp. SYK-6 (β-etherases Lig E and Lig F, glutathione lyase Lig G). Careful elucidation of the structural modifications occurring in the residual lignins associated with the identification and quantification of the generated low-molecular-weight compounds showed that (i) the laccase-Lig system cleaves non-phenolic aryl glycerol β-O-4 aryl ether bonds, and (ii) the overall reactivity is heavily dependent on the individual lignin structure. More specifically, samples with low phenolic/aliphatic OH groups ratio undergo net depolymerization, while an increased phenolic/aliphatic OH ratio results in the polymerization of the residual lignin irrespective of its botanical origin and isolation process.

Looking at the Distant Universe with the MeerKAT Array: Discovery of a Luminous OH Megamaser at z > 0.5

In the local universe, OH megamasers (OHMs) are detected almost exclusively in infrared-luminous galaxies, with a prevalence that increases with IR luminosity, suggesting that they trace gas-rich galaxy mergers. Given the proximity of the rest frequencies of OH and the hyperfine transition of neutral atomic hydrogen (H i), radio surveys to probe the cosmic evolution of H i in galaxies also offer exciting prospects for exploiting OHMs to probe the cosmic history of gas-rich mergers. Using observations for the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep H i survey, we report the first untargeted detection of an OHM at z > 0.5, LADUMA J033046.20−275518.1 (nicknamed “Nkalakatha”). The host system, WISEA J033046.26−275518.3, is an infrared-luminous radio galaxy whose optical redshift z ≈ 0.52 confirms the MeerKAT emission-line detection as OH at a redshift z OH = 0.5225 ± 0.0001 rather than H i at lower redshift. The detected spectral line has 18.4σ peak significance, a width of 459 ± 59 km s−1, and an integrated luminosity of (6.31 ± 0.18 [statistical] ± 0.31 [systematic]) × 103 L ⊙, placing it among the most luminous OHMs known. The galaxy’s far-infrared luminosity L FIR = (1.576 ±0.013) × 1012 L ⊙ marks it as an ultraluminous infrared galaxy; its ratio of OH and infrared luminosities is similar to those for lower-redshift OHMs. A comparison between optical and OH redshifts offers a slight indication of an OH outflow. This detection represents the first step toward a systematic exploitation of OHMs as a tracer of galaxy growth at high redshifts.