Advanced Materials Research Vols. 455-456

Abstract: The3,6,8-tribromo-7-hydroxy-4-methylcoumarin (a) and 7-acetoxy-4-bromomethyl coumarin (b) have been prepared and characterized by IR and NMR spectum, and thermal analyses. The crystal and molecular structures of them were determined by X-ray diffraction methods. The compound (a) crystallizes in Orthorhobmic system, space group Pbca, with lattice parameters a = 8.3346(9), b =16.2420(19), c =16.726(2) Å, α=β=γ=90°, Mr= 412.87, V = 2264.2(5) ų, Z = 8, Dc= 2.422 g/cm³, F(000) = 1552, R = 0.0575 and wR = 0.0817. The compound (b) crystallizes in Triclinic system, space group P-1, with lattice parameters a = 7.6540(15), b = 7.6880(15), c = 10.654(2) Å, α = 101.49(3), β = 98.32(3), γ = 103.68(3)°, Mr = 297.10, V = 584.7(2) ų, Z = 2, Dc = 1.688 g/cm³, F(000) = 296, R = 0.0578 and wR = 0.1353. In the (a) structure, The three Br-C bond distances are in the range of 1.870(8) ~ 1.894(6) Å. In the (b) structure, The Br-C bond distance is 1.956 (6) Å. The IR spectral data are in agreement with the structural data. The band at 577 cm^-1 , 582cm^-1 in the compound (a) and (b) could be assigned to the v_C-Br stretching vibration. Because of the hydrogen bonds and π-π stacking between 1,2-benzopyrone rings and 1,2-benzopyrone rings of the adjacent molecule. The title compound also shows good fluorescent behaviors.

Abstract: The aim was to provide scientific basis for development and utilization of pinus elliottii engelm resources.As the raw material, pines needles of pinus elliottii were moistened first by vaporization medium. After that, the needles were processed in advance by microwave to change tissues of needles, and finally, the Shikimic acid was extracted from the needles in hot water. Meanwhile, the extraction method is compared with traditional one in the paper. As a result, the perfect technological conditions were gained for extraction of Shikimic acid by microwave preprocessing. The method is: moistening pine needles within 15 minutes in 70% ethanol water which was 1.6 times weight of needles, then, processing the needles for 60 seconds by 70W microwave. The processing time should increase 30 seconds every 5-gram material added. Finally, the extraction lasted over 30 minutes adding 25-time hot water at 80°C. Seven eighths of extraction time by microwave preprocessing is shortened compared by the traditional extraction method, and extraction ratio for Shikimic acid raises by 35.8%.

Abstract: - Electrochemical impedance spectroscopy (EIS) was used to study the thickness and curing temperature influence on the aging behavior of polyaspartic ester (PAE) polyurea under salt fog exposure in this paper. The result has demonstrated that coating thickness and curing temperature had great influence on aging behavior of the PAE-t-HDI prepolymer-D2000H65 aliphatic polyurea (T3). The low frequency impedance after 1day exposure increased from 5.31×1010Ω·cm to 7.96×1010Ω while coating thickness was increased from 40μm to 200μm, and the low frequency impedance of 200μm coating was 7.42×1010Ω·cm2 high after 200 days exposure. The low frequency impedance after 1day and 200 days exposure increased by 0.83×1010 Ω·cm2 and 0.39×109Ω·cm2 respectively, while curing temperature were increased from 60°C to 80°C. Suggestions have been made, namely that increase the coating thickness and curing temperature can improve low frequency impedance of PAE polyurea, as a result, improve the protective properties of the coatings.

Abstract: . The comprehensive performance of three kinds of surface preparation systems of polyurea coatings for Beijing-Shanghai High-Speed Railway bridge concrete beams’ protection both in situ and in lab were studied in this paper. The pull-off test and visual inspection were used to determine the adhesion and coverage effect of the bug hole of shot blasted concrete surface. Adhesion tests were conducted both in situ and in lab over a period of 1 year. Five failure models were identified based on the failure mechanisms observed during the tests. It showed that, the adhesion strength of Qtech-112 system increased initially (from 2.7 to 4.8 MPa) and then tended to be stable (about 4.5MPa) both in lab and in situ, E1 and E2 system increased initially (from 1.2 to 1.9 MPa) then decreased to 1.3 MPa under low temperature. The tack free time of Qtech-112 was about 3 hours less than E1 and E2 system. Accordingly, the adhesion and tack-free time of epoxy based system (E1, E2) was very sensitive to application temperature and humidity in jobsite. Polyurethane based system (Qtech-112) have a good adhesion and surface coverage effect to concrete surfaces than epoxy based system under the same ambient condition, it showed an excellent comprehensive performance than epoxy one (E1, E2) both in adhesion and in elimination of pinhole for upcoming polyurea application.

Abstract: One of the negative factors of thermal is the effect on the adhesion of polymer coating. The high difference of thermal expansion coefficient between epoxy system and substrate is far, so put forward a new substrate system base on polyurethane (QTECH-112 system). To study the thermal change situation, the static strain testing and the substrate system microstrain change situation on low temperature and common temperature were tested respectively, and the mircostrain at the corners of the structure had also been tested. Results showed that both substrate systems had little microstrain in common temperature. But the epoxy system had high shrink strain under the low temperature, and caused the thermal stress, wihch could not be neglected during the concrete ; As a polyurethane elastomer, QTECH-112 system’s, thermal stress reduced by stress relaxation. The boundary of structure had limited on strain, so it should considered on structure design.

Abstract: . This paper mainly studied the properties of PAE polyurea coated concrete under coactions of salt fog and freeze-thaw. After exposed salt fog conditions for 200d, T3, B2, F2 and TM four coated concrete relative dynamic elastic modulus have small changes, but different coated concrete variation amplitude is different. T3 coated concrete after 100 times of freeze-thaw cycle the relative dynamic elastic modulus began to drop, 200 times freeze-thaw cycle ends, relative dynamic elastic modulus variation is the largest, decrease rate is 95%, TM concrete during 200 times freeze-thaw cycle, relative dynamic elastic modulus almost no change, B2 concrete and F2 concrete the extent of change between coating T3 and TM. After 300 times the freeze-thaw cycle coated concrete didn't appear freeze-thaw damage phenomenon. Four kinds of coating concrete relative dynamic elastic modulus variation by large to small order: T3 coated concrete > B2 coated concrete >F2 coated concrete > TM coated concrete, concrete with the same 200d rule. Frost resistance order, by contrast, TM coated concrete > B2 coated concrete > F2 coated concrete > T3 coated concrete.

Abstract: - In this study, sodium alginate based porous membrane adsorbents (GA/SA) were prepared by using polyethylene glycol (PEG) as porogen and glutaraldehyde (GA) as cross-linking agent. The prepared GA/SA were used to remove Cr (III) ions from wastewater to test its adsorption performance. The proposed technique is very convenient for operation. The batch experiments were performed to investigate the adsorption kinetics of Cr (III) ions from aqueous solution under different conditions, such as the amount of PEG in the GA/SA, pH of solution, initial Cr (III) ions concentration, adsorbent dose and contact time. The GA/SA exhibited the maximum uptake capacity of 57.4 mg/g under the optimal condition. The experiment results show that the adsorption is high pH-dependent. Various kinetic models were applied to examine the mechanism of adsorption processes. Pseudo-second-order kinetic model exhibits the best correlation with experimental data. The kinetic experiment results show that the adsorption of Cr (III) ions is a multistep limited adsorption process. Out of Langmuir and Freundlich isotherm equations, the batch equilibrium data are better described by the Freundlich isotherm equation. The prepared GA/SA could be considered as a potential low-cost and high-effective bio-sorbent for removing and recovering Cr (III) ions from the aqueous solutions.

Abstract: The hydrogenation of biomass-derived ethyl lactate was studied over several ruthenium catalysts. The effect of support (TiO₂, SiO₂, γ-Al₂O₃, NaY and active-carbon) on the catalytic performance was evaluated. The ruthenium catalysts were characterized by inductively coupled plasma (ICP), N₂ physisorption, powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The catalytic performance of the ruthenium catalysts is dependent on the intrinsic property of the support. Ru/SiO₂ was found to be an efficient catalyst for the hydrogenation of ethyl lactate to 1,2-propanediol (1,2-PDO).

Abstract: The conducting properties of mixed reverse micelles formed with amphiphilic ionic liquids (DomimBF4) and cetyltrimethylammonium bromide (CTAB) have been investigated, with the emphasis on the effect of cosurfactants, surfactant compostion. In DomimBF4/CTAB/ n-butanol/ cycloheane system, a percolation in conductance phenomenon was observed, the percolation threshold Wp depends upon the content of DomimiBF4. The influence of cosurfactants on the conductomery properties of mixed reverse micelles was studied in detail.

Abstract: - 5-amino-2(p-aminophenyl) benzoxazole (AAPB) and its derived polyimide prepared with pyromellitic dianhydride (PMDA) were synthesized successfully. Their structures were characterized by FT-IR, ¹H NMR, Element analysis, ¹³C NMR, Solid-state ¹³CNMR, DSC, TG and XRD. The polyimide was synthesized via a conventional two-stage method. The intermediate poly (amic acid) had inherent viscosity of 1.06dL/g and could be thermally converted into light yellow polyimide film. The polyimide showed excellent solvent resistance and good thermal stability. The glass transition temperature (T_g) was found to be 314°C, the decomposition started at a temperature above 500°C in air and above 550°C in argon atmosphere. The thermal degradation of the polyimide was studied by thermogravimetric analysis (TGA) in order to determine the actual reaction mechanisms of the decomposition process. The apparent activation energy (E_a) was obtained following Flynn-Wall-Ozawa method. The activation energies of different mechanism models and pre-exponential factor (A) were determined by Coats-Redfern method. Compared with the value obtained from the Ozawa method, the actual reaction mechanism obeyed three-dimensional diffusion model, Jander equation (D₃) with integral form g(α)=[1-(1-α)^1/3]².