reaction rate
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S. B. Dubovichenko ◽  
N. A. Burkova ◽  
R. R. Shamitova

2022 ◽  
Guomin Wu ◽  
Jian Chen ◽  
Zhaozhe Yang ◽  
Can Jin ◽  
Guifeng Liu ◽  

Abstract Due to the complex heterogeneous film forming process of two-component waterborne polyurethane (2K-WPU), the crosslinking reaction rate of 2K-WPU cannot meet the demand of efficient application in coatings. In order to improve the crosslinking reaction rate of 2K-WPU, a waterborne polyol containing tertiary amine groups was synthesized from rosin based epoxy resin and secondary amine compound, and then autocatalytic 2K-WPU was prepared by crosslinking the rosin based waterborne amino polyol with polyisocyanate. The structure of the polyol from rosin based epoxy resin was characterized with Fourier infrared (FT-IR) and nuclear magnetic resonance (NMR). The crosslinking kinetics and the crosslinked product of the rosin based waterborne amino polyol were also compared with a commercial acrylic polyol. It was shown from the results that the crosslinking reaction rate of the rosin based waterborne amino polyol was faster than that of the commercial acrylic polyol, which indicated the tertiary amine groups chemically bonded in the rosin based polyols could autocatalyze the crosslinking reaction of 2K-WPUs with catalysts free. The film of the rosin based waterborne amino polyol had excellent impact strength, adhesion, flexibility, hardness, gloss, fullness and solvent resistance, showing a good application prospect in the field of waterborne coatings.

2022 ◽  
Vol 105 (1) ◽  
D. S. Harrouz ◽  
N. de Séréville ◽  
P. Adsley ◽  
F. Hammache ◽  
R. Longland ◽  

2022 ◽  
Vol 119 (3) ◽  
pp. e2110776118
Masaoki Uno ◽  
Kodai Koyanagawa ◽  
Hisamu Kasahara ◽  
Atsushi Okamoto ◽  
Noriyoshi Tsuchiya

Hydration and carbonation reactions within the Earth cause an increase in solid volume by up to several tens of vol%, which can induce stress and rock fracture. Observations of naturally hydrated and carbonated peridotite suggest that permeability and fluid flow are enhanced by reaction-induced fracturing. However, permeability enhancement during solid-volume–increasing reactions has not been achieved in the laboratory, and the mechanisms of reaction-accelerated fluid flow remain largely unknown. Here, we present experimental evidence of significant permeability enhancement by volume-increasing reactions under confining pressure. The hydromechanical behavior of hydration of sintered periclase [MgO + H2O → Mg(OH)2] depends mainly on the initial pore-fluid connectivity. Permeability increased by three orders of magnitude for low-connectivity samples, whereas it decreased by two orders of magnitude for high-connectivity samples. Permeability enhancement was caused by hierarchical fracturing of the reacting materials, whereas a decrease was associated with homogeneous pore clogging by the reaction products. These behaviors suggest that the fluid flow rate, relative to reaction rate, is the main control on hydromechanical evolution during volume-increasing reactions. We suggest that an extremely high reaction rate and low pore-fluid connectivity lead to local stress perturbations and are essential for reaction-induced fracturing and accelerated fluid flow during hydration/carbonation.

2022 ◽  
Vol 5 (1) ◽  
pp. 23
Minghan Qu ◽  
Tong He ◽  
Tianyi Liu ◽  
Chensha Li

The in-situ reaction process was used to prepare composite materials loaded with cadmium sulfide, which were respectively loaded by carbon nanotubes, activated carbon, and carbon nanotube/activated carbon composites for the study of photocatalytic degradation of methyl orange. The results show that when carbon nanotubes and activated carbon are used as carriers, the photocatalytic degradation reaction rate constants are 3.6 times and 8.8 times higher than those without a carrier. The photocatalytic performance of the carbon nanotube/activated carbon composite carrier with a mass ratio of 20: 80 to support cadmium sulfide is significantly higher than that of cadmium sulfide supported by carbon nanotubes and activated carbon respectively, and its photocatalytic degradation reaction rate constant is 30% – 40% higher than that under the condition of activated carbon alone as carrier. It shows that when the modified activated carbon is used as a photocatalyst carrier, carbon nanotubes have a significant effect in improving the efficiency of degrading organic matter.

Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 345
Ioannis S. Tsagkalias ◽  
Dimitrios S. Achilias

Functional groups in a monomer molecule usually play an important role during polymerization by enhancing or decreasing the reaction rate due to the possible formation of side bonds. The situation becomes more complicated when polymerization takes place in the presence of graphene oxide since it also includes functional groups in its surface. Aiming to explore the role of functional groups on polymerization rate, the in situ bulk radical polymerization of hydroxyethyl acrylate (HEA) in the presence or not of graphene oxide was investigated. Differential scanning calorimetry was used to continuously record the reaction rate under both isothermal and non-isothermal conditions. Simple kinetic models and isoconversional analysis were used to estimate the variation of the overall activation energy with the monomer conversion. It was found that during isothermal experiments, the formation of both inter- and intra-chain hydrogen bonds between the monomer and polymer molecules results in slower polymerization of neat HEA with higher overall activation energy compared to that estimated in the presence of GO. The presence of GO results in a dissociation of hydrogen bonds between monomer and polymer molecules and, thus, to higher reaction rates. Isoconversional methods employed during non-isothermal experiments revealed that the presence of GO results in higher overall activation energy due to the reaction of more functional groups on the surface of GO with the hydroxyl and carbonyl groups of the monomer and polymer molecules, together with the reaction of primary initiator radicals with the surface hydroxyl groups in GO.

2022 ◽  
Yufen Han ◽  
Jiaqian Li ◽  
Xiaojin Zhang ◽  
Fan Xia ◽  
Yu Dai

Abstract Regulating catalytic activity plays an important role in further optimizing and developing multifunctional catalysts with high selectivity and high activity. Reversible dual regulation of catalytic activity has always been a challenging task. Here, we prepared poly(N-isopropylacrylamide)-anchored gold nanoparticles ([email protected]) through host-guest interaction of cyclodextrin capped gold nanoparticles ([email protected]) and azobenzene-terminated poly(N-isopropylacrylamide) (Azo-PNIPAM). Azo-PNIPAM as thermal and light responsive ligand allows reversible dual regulation of catalytic activity. When the temperature is higher than the lowest critical solution temperature (LCST), the PNIPAM chain shrinks rapidly, increasing the steric hindrance around AuNPs and reducing the catalytic activity. Under ultraviolet light irradiation, cis-azobenzene disassembles from cyclodextrin and the number of surface active sites of AuNPs increases, which improves the catalytic activity. The reaction rate of UV irradiation is almost 1.3 times that of visible light irradiation. This work provides a simple and effective strategy for the construction of reversible catalysts.

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