A novel form stable phase change material with comb-like cross-linked polyurethane as supporting skeleton.

To improve the homogeneity of phase-change materials (PCMs) composites for thermal energy storage, the poly(ethylene glycol monomethyl ether)-based trimethylolpropane (Ymer-N120) with long side ethyoxyl chains is employed to form comb-like polyurethane which functioned as supporting materials for PCMs. And the results of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, differential scanning calorimetry, accelerated thermal cycling testing, thermogravimetric analysis and field emission scanning electron microscopy (FESEM) suggested a crosslinked polyurethane embedded with micron grade myristic acid (MA) crystals was prepared during the thermal curing process. The obtained comb-like polyurethane (YP) can provide 3D structure supporting materials for melting MA. And the long side ethyoxyl chain of Ymer-N120 promote the melting MA form micron-sized crystals. The results of thermal reliability testing confirmed the advantages of same methylene groups in side chains and suggested the maximal hold capability of YP crosslinks is about 50 wt% of composites. With the 50 wt% addition of MA, YPM50 can supply high latent heat (over 90 J/g of YPM50) with fine thermal stability (due to its initial decomposing temperature reaches 190 °C) without leakage (after 500 times of accelerated thermal cycling testing). All results indicated this structure supplies an effective solution for the leakage of PCMs, which show a promising application in TES.

Alkyl Titanate-Modified Graphene Oxide as Friction and Wear Reduction Additives in PAO Oil.

Diacetoxy-stearoyloxy-titanium-modified graphene oxide (Titanate-GO) was successfully prepared using titanium tetraisopropanolate, stearic acid, acetic acid, and graphene oxide (GO). The morphology and structure of the as-prepared materials were tested by FT-IR, Raman, TG/DSC, SEM, and TEM instruments. The results indicate that long alkyl titanium chains have been grafted on the surface of a GO sheet, which guaranteed the dispersibility of Titanate-GO in PAO10 base oil. Then, the lubrication properties of Titanate-GO as a lubricating additive in PAO10 base oil were evaluated on a four-ball machine. The results show that the average coefficient of friction and wear scar diameter were reduced by 49.5 and 28.2%, respectively, compared with bare PAO10 base oil. Finally, the lubrication mechanism was discussed based on the Raman analysis, which was carried out on the worn surface of the steel ball.

Novel MoS2-DOPO Hybrid for Effective Enhancements on Flame Retardancy and Smoke Suppression of Flexible Polyurethane Foams.

A novel MoS2-DOPO hybrid has been successfully synthesized through the grafting of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) on the surface of MoS2 nanosheets using allyl mercaptan as an intermediate. MoS2-DOPO was used as a flame retardant additive to prepare flame-retardant flexible polyurethane foam (FPUF). The influence of MoS2-DOPO on the mechanical, thermal stability, and flame retardancy properties of FPUF composites were systematically investigated. The incorporation of MoS2-DOPO could not deteriorate greatly the tensile strength and 50% compression set of FPUF composites, but effectively improves the char residue. The cone calorimeter and smoke density tests results revealed that the peak heat release rate, total heat release, and the maximum smoke density of the MoS2-DOPO/FPUF composite were reduced by 41.3, 27.7, and 40.5%, respectively, compared with those of pure FPUF. Furthermore, the char residue after cone calorimeter tests and pyrolysis gaseous products of the MoS2-DOPO/FPUF composite were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and thermogravimetric analysis/infrared spectrometry. The results suggested that the MoS2-DOPO hybrid played a synergistic flame retardant effect of gas and condensed bi-phase action. In addition, a possible flame retardancy and smoke suppression mechanism of the MoS2-DOPO/FPUF composite were proposed. This study provides a facile and promising strategy for the fabrication of polymer materials with excellent flame retardancy and smoke suppression properties.

Thermal Stability and Flame Retardancy Properties of Epoxy Resin Modified with Functionalized Graphene Oxide Containing Phosphorus and Silicon Elements.

Phosphorus- and silicon-modified graphene oxide was prepared to improve the thermal stability and flame retardancy properties of epoxy resin. 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and vinyltriethoxysilane (VTES) were successfully grafted onto the surface of graphene oxide (GO) through solvothermal synthesis and hydrolysis-condensation reaction, respectively. Subsequently, the functionalized graphene oxide grafted by DOPO and VTES (DOPO-VTES-GO) was incorporated into the epoxy resin by the solution blending method. The effect of DOPO-VTES-GO on the thermal stability and flame-retardant properties of epoxy resin was systematically studied. Thermogravimetric analysis showed that the thermal stability and char residue yield of DOPO-VTES-GO/epoxy were increased obviously compared with those of pure epoxy resin and DOPO-GO/epoxy. Cone calorimeter test results showed that DOPO-VTES-GO/epoxy had better flame retardancy than pure epoxy resin and DOPO-GO/epoxy on reducing the peak of heat release rate, total heat release, and total smoke production. Furthermore, the char residue after the cone calorimeter tests was investigated by scanning electron microscopy-energy-dispersive X-ray spectrometry, Raman spectroscopy, and Fourier transform infrared measurements. These results demonstrated that the DOPO-VTES-GO can enhance the graphitization degree of char residues and promote the formation of the thermally stable char. In addition, the mechanism of flame retardancy was proposed, and DOPO-VTES-GO exerts the synergistic effect mainly by means of catalytic charring in the condensed phase and capturing hydroxyl or hydrogen radicals from thermal decomposition of epoxy resin in the gas phase. This work provides novel insights into the preparation of phosphorus-silicon-graphene oxide ternary synergistic flame retardants for thermosetting polymer materials.

A Hybrid Coumarin-Semifluorescein-Based Fluorescent Probe for the Detection of Cysteine.

A new type of turn-on fluorescent probe CF-AC for the detection of Cys was firstly reported. The probe exhibited an excellent response to Cys with high selectively and sensitivity. In the presence of Cys, two fluorescence emission peaks at 525 nm and 650 nm appeared accompanied by the fluorescence color change from blue to red. Morever, the probe had good biocompatibility and could be successfully used for fluorescence imaging of Cys in MCF-7 cells.

Kinetics and mechanism for the sonophotocatalytic degradation of p-chlorobenzoic acid.

The advanced oxidation processes of sonolysis (213 kHz), photocatalysis, and a hybrid combination of both (sonophotocatalysis) have been used in the degradation of a representative aromatic carboxylic acid, p-chlorobenzoic acid (PCBA), in ambient air saturated aqueous solutions. The formation of degradation products were monitored quantitatively and qualitatively using HPLC and MS/MS. A kinetic model was used to account for the degradation of the PCBA in the presence of intermediate degradation products and also their formation and subsequent degradation. Under certain experimental conditions a small (20% enhancement) synergistic effect in the degradation rate was evident in the combined process compared with the sum of the individual processes.

The mechanism of sonophotocatalytic degradation of methyl orange and its products in aqueous solutions.

In this study, it was found that a hybrid technique, sonophotocatalysis, is able to degrade a parent organic pollutant (methyl orange) as well as its by-products. The analysis of products formed during the whole degradation has demonstrated that the pH or the selection of oxidation process (sonolysis/photocatalysis/sonophotocatalysis) is able to control the degradation pathway. It was shown in the by-products analysis that the solution pH can alter the amount of each product generated during the sonophotocatalytic degradation. It was revealed that the different degradation rates of methyl orange and its products result from the solution pH and the nature of the organic products. Furthermore, a comparison of the data obtained from the oxidation processes on the degradation of the reaction intermediates identified the advantages of the combined system. It is concluded that sonophotocatalysis is capable of yielding a more complete and faster mineralization of organic pollutants than the individual processes. However, as in the degradation of the parent compound, the overall mineralization is lower than an additive effect (negative synergistic effect).

Sonochemically prepared platinum-ruthenium bimetallic nanoparticles.

Colloidal bimetallic nanoparticles of Pt-Ru have been synthesized by sonochemical reduction of Pt(II) and Ru(III) in aqueous solutions. Transmission electron microscope (TEM) images indicate that sequential reduction of the Pt(II) followed by the Ru(III) produces particles with a core shell (Pt@Ru) morphology. In the presence of sodium dodecyl sulfate, SDS, as a stabilizer, the particles have diameters between 5 and 10 nm. When polyvinyl-2-pyrrolidone, PVP, is used as the stabilizer, the rate of reduction is much faster, giving ultrasmall bimetallic particles of approximately 5 nm diameter.