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71.
Choudhary V. Varma H. S. Varma I. K. 《Journal of Thermal Analysis and Calorimetry》1987,32(2):579-593
The effects of EPDM rubber on the crystallization behaviour of isotactic polypropylene (iPP) in the ternary iPP/HDPE/EPDM blends were studied by means of DSC and X-ray diffraction. Analysis of the crystallization exotherm peaks in terms of crystallization nucleation and growth rates and crystallinity revealed variations in the morphology of the iPP component in the blends as a function of the EPDM content. The DSC and X-ray diffraction results showed that the overall crystallinity decreased as the weight percentage of EPDM was increased in the iPP/HDPE blends.The morphology of these blends was studied by scanning electron microscopy, which revealed a random distribution of EPDM throughout the iPP matrix. The size and number of these rubber particles increased with increase of the EPDM weight percentage in the ternary iPP/HDPE/EPDM blends. The probable existence of composite inclusions of EPDM-HDPE in an iPP matrix is suggested.
Zusammenfassung Die Effekte von EPDM-Kautschuk auf das Kristallisationsverhalten von isotaktischem Polypropylen (iPP) in den ternären Gemischen iPP/HDPE/EPDM wurden mittels DSC und Röntgendiffraktometrie untersucht. Die Analyse der exothermen Kristallisationspeaks mit Hinblick auf die Kristallisationskeimbildung und die Geschwindigkeit des Kristallwachstums und die Kristallinität deuten auf morphologische Varianten der iPP-Komponente in den Gemischen in Abhängigkeit vom EPDM-Gehalt hin. Die durch DSC und Röntgendiffraktometrie erhaltenen Ergebnisse zeigen, daß die Kristallinität mit steigendem Gehalt an EPDM in den iPP/HDPE-Gemischen abnimmt. Die Morphologie dieser Gemische wurde durch Scanningelektronenmikroskopie untersucht. Es wurde eine random-Verteilung des EPDM in der iPP-Matrix festgestellt. Größe und Zahl dieser Kautschukpartikel nehmen mit zunehmendem EPDM-Gewichtsanteil in den ternären iPP/HDPE/EPDM-Gemischen zu. Auf die wahrscheinliche Existenz von EPDM/HDPE-Einschlüssen in einer iPP-Matrix wird hingewiesen.
(-) - -. , , , . , --. , . ---. - - .相似文献
72.
(+)-Xyloketal D was prepared in a one-pot multistep domino reaction by heating optically active 5-hydroxy-4-methyl-3-methylenepentan-2-one (R) in toluene with 2,4-dihydroxyacetophenone. The absolute configuration of the natural product was confirmed by preparation of the starting enone from a lactone of established absolute configuration. 相似文献
73.
Z. Iqbal 《Chemical physics letters》1976,40(1):41-44
The phase changes in polycrystalline ammonium nitrate and its fully deuterated analogue have been studied by Raman scattering. The phase V and IV transition was found to be associated with the softening and intensity decrease of a NO3? librational mode. The Raman line-width data suggest that the VII to V phase transition involves a change in the degree of orientational order of the ions without incurring a change in lattice structure. 相似文献
74.
The present paper describes the synthesis of 5‐azido‐6‐ketones (14) and 6‐hydroxy‐5‐ketone (20) from Hajos Wiechert ketone as chiral building blocks for cephalostatin analogues. The synthesis of symmetric cephalostatin analogue from 6‐hydroxy‐5‐ketone has also been reported. The characterization of the each synthesized compounds was carried out by IR, 1H‐NMR, 13C‐NMR and High resolution Mass Spectrometry. 相似文献
75.
Jayasinghe UL Kumarihamya BM Nadeemb M Choudhary MI Atta-Ur-Rahmanb Weerasooriya A 《Natural product letters》2001,15(3):151-155
Chemical investigation of the non-quaternary alkaloidal fraction of the aerial parts of Sarcococca zeylanica of the family Buxaceae furnished a steroidal alkaloid iso-N-formyl-5-en-chonemorphine, which has not been previously reported as a natural product. The structure of this alkaloid was established on the basis of spectroscopic evidence. 相似文献
76.
The evolving nature of a Stillinger-Weber modeled silicon glass is studied using two accelerated molecular dynamics scheme, specifically, hyperdynamics and self-guided algorithms due to Voter and due to Wu and Wang, respectively. We obtain an acceleration of the dynamics, a "boost," on the order of 20 without incurring any significant computational overhead. The validity of the results using accelerated methods is provided by comparison to a conventional molecular dynamics (MD) algorithm simulated under constant temperature conditions for more than 100 ns. We found that performing a sensitivity analysis of the effect of the parameters lambda and t1 before applying the self-guided MD scheme was important. Values of lambda greater than 0.1 and t1 equal to 1 ps were found to give improved structural evolution as compared to a conventional MD scheme. The hyperdynamics approximation scheme was found to be effective in obtaining boosts in the range of 4-12 for a small system without changing the dynamics of the evolution. However, for a large system size such an approach introduces significant perturbations to the pertinent equations of motion. 相似文献
77.
Muhammad Nawaz Tahir Lela Gorgishvili Jixue Li Tatiana Gorelik Ute Kolb Lutz Nasdala Wolfgang Tremel 《Solid State Sciences》2007,9(12):1105-1109
Crystalline ZrO2 nanoparticles were prepared from zirconium isopropoxide by slow hydrolysis and subsequent hydrothermal treatment of solutions containing various amounts of sodium hydroxide at 180 °C. Whereas moderately basic solutions lead to the formation of nanoparticles of monoclinic ZrO2 with plate-like morphology, and nanoparticles of the cubic ZrO2 high-temperature polymorph with diameters of approx. 5 nm were obtained from strongly basic solutions. The morphology, structure and properties of as-synthesized nanoparticles were characterized using HRTEM, XRD, Raman spectroscopy, UV–vis, PL spectroscopy and BET measurements. The formation of both, the monoclinic and the cubic polymorph, was confirmed by electron microscopy and Raman spectroscopy. The crystallinity and morphology of the resulting ZrO2 nanoparticles can be adjusted by the choice of the reaction conditions. The cubic ZrO2 nanoparticles have a high surface area (300 m2/g) and exhibit a strong photoluminescence in the UV region. 相似文献
78.
Some new N‐glycosides of 4‐(2‐phenylethyl)‐5‐pyridyl‐1,2,4‐triazole‐3‐thiones were synthesised by the coupling reaction of halo sugar with 4,5‐disubstituted 3H‐1,2,4‐triazole‐3‐thiones in the presence of mercuric cyanide and dry nitromethane as solvent, followed by deprotection using dry ammonia in methanol. All of the above compounds were fully characterized by means of infrared, 1H NMR spectroscopy, mass spectroscopy and elemental analysis. 相似文献
79.
Curing of diglycidyl ether of bisphenol-A (DGEBA) with phosphorus containing amide amines i.e. bis[3(3’-aminobenzamido phenyl)]methyl
phosphine oxide (MB),bis[3(4’-aminobenzamido phenyl)]methyl phosphine oxide (PB), tris[3(3’-aminobenzamidophenyl)] phosphine
oxide (MT) and tris[3(4’-aminobenzamido phenyl)] phosphine oxide (PT)and conventionally used curing agent 4,4’-diaminodiphenyl
sulfone (D) was studied by DSC. The amines MB, PB, MT and PT were synthesised in the laboratory and were characterized by
determining elemental composition, melting point, and amine equivalent. Structural characterization was done by 1H-NMR and FTIR. The onset temperature of curing depended on the nucleophilicity of the amines and was in the orderMT≈MB<PT<PB<D.
The exothermic peak temperatures were in the orderD>PB>PT>MT≈MB. The char residue of cured epoxy resin was significantly higher
when phosphorus was incorporated in the cured network. Using mixed amine formulations based on amine D and P-containing amines
and the molar ratio of these amines could easily control the curing characteristics. A linear relationship between char yield
and P-content was observed in such formulations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
80.
The sorptive potential of sunflower stem (180-300 μm) for Cr(III) ions has been investigated in detail. The maximum sorption (≥85%) of Cr(III) ions (70.2 μM) has been accomplished using 30 mg of high density sunflower stem in 10 min from 0.001 M nitric and 0.0001 M hydrochloric acid solutions. The accumulation of Cr(III) ions on the sorbent follows Dubinin-Radushkevich (D-R), Freundlich and Langmuir isotherms. The isotherm yields D-R saturation capacity Xm = 1.60 ± 0.23 mmol g−1, β = −0.00654 ± 0.00017 kJ2 mol−2, mean free energy E = 8.74 ± 0.12 kJ mol−1, Freundlich sorption capacity KF = 0.24 ± 0.11 mol g−1, 1/n = 0.90 ± 0.04 and of Langmuir constant KL = 6800 ± 600 dm3 mol−1 and Cm = 120 ± 18 μmol g−1. The variation of sorption with temperature (283-323 K) gives ΔH = −23.3 ± 0.8 kJ mol−1, ΔS = −64.0 ± 2.7 J mol−1 K−1 and ΔG298k = −4.04 ± 0.09 kJ mol−1. The negative enthalpy and free energy envisage exothermic and spontaneous nature of sorption, respectively. Bisulphate, Fe(III), molybdate, citrate, Fe(II), Y(III) suppress the sorption significantly. The selectivity studies indicate that Cr(III), Eu(III) and Tb(III) ions can be separated from Tc(VII) and I(I). Sunflower stem can be used for the preconcentration and removal of Cr(III) ions from aqueous medium. This cheaper and novel sorbent has potential applications in analytical and environmental chemistry, in water decontamination, industrial waste treatment and in pollution abatement. A possible mechanism of biosorption of Cr(III) ions onto the sunflower stem has been proposed. 相似文献