Preparation of Yellowing-Resistant Waterborne Polyurethane Modified with Disulfide Bonds.

Waterborne polyurethane, renowned for its lightweight properties, excellent insulation capabilities, and corrosion resistance, has found extensive application in fields such as construction, automotive, leather, and thermal insulation. Nevertheless, during operational usage, waterborne polyurethane materials, akin to other polymeric substances, are susceptible to oxidative aging manifestations like yellowing, cracking, and diminished mechanical performance, significantly curtailing their utility. Consequently, the synthesis of yellowing-resistant polyurethane assumes pivotal significance. This study integrates dynamic reversible reactions into the synthesis process of polyurethane by introducing the dynamic reversible compound 2-hydroxyethyl disulfide as a chain extender, alongside the incorporation of a UV absorber to enhance the polyurethane's resistance to yellowing. When the disulfide bonds absorb heat, they undergo cleavage, yielding thiols that spontaneously recombine into disulfide bonds at ambient temperatures, allowing for the continuous breaking and reformation of disulfide bonds to absorb heat. Concurrently, in collaboration with the UV absorber, the detrimental effects of ultraviolet radiation on the polyurethane material are mitigated, thereby augmenting its resistance to yellowing. This study scrutinizes the positioning of UV absorber addition, the quantity of UV absorber, and the molar ratio of 1,4-butanediol to 2-hydroxyethyl disulfide, characterizing the functional groups of polyurethane through infrared and Raman spectroscopy. It is observed that the successful preparation of yellowing-resistant polyurethane is achieved, and evaluations on the modified polyurethane through color difference, tensile, and centrifugal tests reveal that the optimal yellowing resistance is attained by adding a UV absorber at a mass fraction of 1% to 3% prior to chain extension, resulting in a color change grade of 2, denoting slight discoloration. Simultaneously, the other properties of polyurethane exhibit relative stability. Notably, when the molar ratio of 1,4-butanediol to 2-hydroxyethyl disulfide is 3:2, the overall performance of the polyurethane remains stable, with exceptional yellowing resistance capabilities attaining a color change grade of 2.

Exploring the mechanistic role of alloying elements in copper-based electrocatalysts for the reduction of carbon dioxide to methane.

The promise of electrochemically reducing excess anthropogenic carbon dioxide into useful chemicals and fuels has gained significant interest. Recently, indium-copper (In-Cu) alloys have been recognized as prospective catalysts for the carbon dioxide reduction reaction (CO2RR), although they chiefly yield carbon monoxide. Generating further reduced C1 species such as methane remains elusive due to a limited understanding of how In-Cu alloying impacts electrocatalysis. In this work, we investigated the effect of alloying In with Cu for CO2RR to form methane through first-principles simulations. Compared with pure copper, In-Cu alloys suppress the hydrogen evolution reaction while demonstrating superior initial CO2RR selectivity. Among the alloys studied, In7Cu10 exhibited the most promising catalytic potential, with a limiting potential of -0.54 V versus the reversible hydrogen electrode. Analyses of adsorbed geometries and electronic structures suggest that this decreased overpotential arises primarily from electronic perturbations around copper and indium ions and carbon-oxygen bond stability. This study outlines a rational strategy to modulate metal alloy compositions and design synergistic CO2RR catalysts possessing appreciable activity and selectivity.

Synthesis of acrylic resin and methacrylic resin microspheres by suspension polymerization.

The process of suspension polymerization was utilized to create acrylate resin microspheres with mesh numbers of 140-200 µm and particle sizes of 100 µm for implementation in mesh coating technology. The copolymer of methyl methacrylate (MMA) and methyl acrylate (MA) served as the primary polymer, with dibenzoyl peroxide (DBPO) functioning as the initiator, and a mixture of calcium carbonate and deionized water served as the dispersion medium. The surface morphology of the synthesized microspheres was analyzed through Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) to confirm successful synthesis. The optimal reaction conditions for the synthesis of these microspheres were determined to be a dispersant dosage of 30 g of calcium carbonate with a monomer ratio of 4:1, a reaction time of 1 h, an initiator dosage of 1.2 g of BPO, and a reaction temperature of approximately 75-80 C, resulting in microspheres with a regular spherical shape and smooth surface.

Mechanically Strong and Tough Poly(urea-urethane) Thermosets Capable of Being Degraded under Mild Condition.

The development of degradable polymeric materials such as degradable polyurethane or polyurea has been much highlighted for resource conservation and environmental protection. Herein, a facile strategy of constructing mechanically strong and tough poly(urea-urethane) (PUU) thermosets that can be degraded under mild conditions by using triple boron-urethane bonds (TBUB) as cross-linkers is demonstrated. By tailoring the molecular weight of the soft segment of the prepolymers, the mechanical performance can be finely controlled. Based on the cross-linking of TBUB units and hydrogen-binding interactions between TBUB linkages, the as-prepared PUU thermosets have excellent mechanical strength of ≈40.2 MPa and toughness of ≈304.9 MJ m-3 . Typically, the PBUU900 strip can lift a barbell with 60 000 times its own weight, showing excellent load-bearing capacity. Meanwhile, owing to the covalent cross-linking of TBUB units, all the PUU thermosets show initial decomposition temperatures over 290 °C, which are comparable to those of the traditional thermosets. Moreover, the TBUB cross-linked PUU thermosets can be easily degraded in a mild acid solution. The small pieces of the PBUU sample can be fully decomposed in 1 m HCl/THF solution for 3.5 h at room temperature.

A Z-scheme Fe2O3/g-C3N4 heterojunction for carbon dioxide to hydrocarbon fuel under visible illuminance.

Graphitic carbon nitride (g-C3N4) is a well-known semiconductor in the photocatalyst which absorbs in the visible region. Ferric oxide (Fe2O3) provides the necessary electron to the valence band of g-C3N4 to refill the deficiency. This system shows the Z-scheme mechanism of the transfer of electrons from the conduction band of Fe2O3 to the valence band of g-C3N4 to reduce the molecular CO2 into the hydrocarbon fuel. The methanol yield obtained was 1768 µmol/g cat. within 24 h in the presence of visible light. The yield of methanol obtained by 15%Fe2O3/g-C3N4 was high than that obtained with g-C3N4 and Fe2O3 under a similar reaction condition. The photocatalysts were characterized by HR-TEM, BET, XPS, XRD, FTIR, TGA-DTA, ICP-AES, UV-vis, Photoluminescence spectroscopy, and Raman spectroscopy. The photocatalyst was highly stable with no leaching and showed nearly constant activity up to five recycling runs.

Preparing copper catalyst by ultrasound-assisted chemical precipitation method.

In this paper, preparing copper catalyst by ultrasound-assisted chemical precipitation method is investigated. The used equipment is JP-020 ultrasonic cleaner, power and frequency are 180 W and 40 kHz respectively. Under the action of ultrasound, CuSO4·5H2O is reduced by ascorbic acid to obtain copper. The products are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and catalytic performance test. The results show that the morphology of copper products is rod-like and irregular granular. Copper catalyst has good catalytic oxidation performance for dyes methylene blue, crystal violet, alizarin red and Rhodamine B. The catalytic efficiency of 10 mg catalyst copper to 6 mg/L methylene blue reaches 98.1%, and the catalytic efficiency of the catalyst increases with the increase of catalyst dosage and the decrease of dye solution concentration. In addition, the new preparation techniques for Cu-based catalysts based on coprecipitation method are compared. Finally, the development trend of the new technology of copper-based catalyst preparation based on coprecipitation method is pointed out.

Base-iodine-promoted metal-catalyst-free reactions of [60]fullerene with ß-keto esters for the selective formation of [60]fullerene derivatives.

In this study, methanofullerenes and 2',3'-dihydrofuran C60 derivatives were selectively synthesized in high yields via the reactions of C60 with ß-keto esters under mild conditions by controlling the addition sequence and molar ratio of iodine and base. The structures of the products were determined by spectroscopic characterization. Moreover, a possible reaction mechanism for the selective formation of fullerene derivatives was proposed.

1H-Imidazol-3-ium-4-carboxyl-ate.

In the title compound, C(4)H(4)N(2)O(2), both imidazole N atoms are protonated and carboxyl-ate group is deprotonated, resulting in a zwitterion. The mol-ecule is essentially planar, with an r.m.s. deviation of 0.012 (1) Å. In the crystal, N-H⋯O hydrogen bonds and π-π stacking inter-actions [centroid-centroid distance = 3.674 (2) Å] between the imidazole rings link the mol-ecules into a three-dimensional supra-molecular network.