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951.
Ultra-high-molecular-weight polyethylene (UHMWPE) – carbon black (CB) blends were prepared by gelation/ crystallization from
PE dilute solutions containing CB particles. The UHMWPE/CB composition chosen were 1/0.15, 1/0.25, 1/0.5, 1/0.75, 1/1, 1/3,
1/5, and 1/9, etc. The cross-linking of PE chains was performed by chemical reaction of dicumyl-peroxide at 160 °C. X-ray diffraction patterns indicate that the crystallinity of PE within the blends decreased drastically through the chemical
reaction at high temperature. The sample preparation method by gelation/crystallization provided the UHMWPE–CB system with
various CB contents up to 90% and the conductivities for the resultant specimens were in the range from 10-9 to 1 Ω-1 cm-1 corresponding to the electric conductivity range of semiconductors. The blends assured thermal stability of electric conductivity
by cross-linking of PE chains, although the mechanical property such as the storage and loss moduli were very sensitive to
temperature. The conductivity of the blends with CB content ≥20% were almost independent of temperature up to 220 °C and the values in the heating and cooling processes were almost the same. On the other hand, for the UHMWPE–CB blends with
13% CB content corresponding to the critical one, temperature dependence of electric resistivity showed positive temperature
coefficient (PTC) effect. The PTC intensities for non-cross-linked and cross-linked materials were lower than that of the
corresponding low-molecular-weight-polyethylene (LMWPE)–CB blend but the maximum peak appeared at 160 °C which is higher than the peak temperature of LMWPE–CB blend.
Received: 10 December 1997 Accepted: 9 April 1998 相似文献
952.
Y. Marcus 《Journal of solution chemistry》1991,20(9):929-944
Taft and Kamlet's -scale of solvent hydrogen bond donation ability is reexamined with regard to its correlations with three widely used polarity scales: Dimroth and Reichardt's E
T
(30), Kosower's Z and Mayer's A
N
, as well as with the m values of the solvents when present as monomeric solutes. The correlation with E
T
serves to extend the solvent -scale according to the expression:
相似文献
953.
Ab initio calculation of the 4-ClC6H4CH2Cl molecule was performed by the restricted Hartree-Fock method in the split valence 6–31 G* basis set with complete optimization of its geometry. Populations of p-orbitals of atoms of this molecule were analyzed.35Cl NQR frequencies and asymmetry parameters of the electric field gradient on35Cl nuclei were estimated on the basis of the populations of valent p-orbitals of CI atoms and their components. Good conformity with the experimental values was obtained when only less diffuse components of p-orbitals were used in calculations of populations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 823–826, April, 1996. 相似文献
954.
I. I. Ponomarev Yu. Yu. Rybkin E. I. Goryunov P. V. Petrovskii K. A. Lyssenko 《Russian Chemical Bulletin》2004,53(12):2881-2883
The reaction of 4,4-dimethyldiphenyl ether with phosphorus trichloride in the presence of anhydrous aluminum chloride was studied. This reaction affords 2,8-dimethyl-10H-105-phenoxaphosphine 10-oxide as virtually the only product. In air, the latter in an alkaline solution is quantitatively transformed into 10-hydroxy-2,8-dimethyl-10H-105-phenoxaphosphine 10-oxide.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2762–2765, December, 2004. 相似文献
955.
D.?Mitra S.?Francis L.?VarshneyEmail author 《Journal of Thermal Analysis and Calorimetry》2004,78(3):821-829
DSC and TG studies were carried out on -radiation processed Indian natural products of medicinal importance, namely Ashwagandha (Withania Somnifera), Amla (Emblica Officinalis) and Hartiki (Terminalia chebula). DSC thermoanalytical curves were recorded from 35 to 400°C in air and nitrogen atmosphere. Similarly, TG thermoanalytical curves were taken from 35 to 700°C in air and nitrogen atmosphere. Irradiated products gave significantly different thermoanalytical profiles in comparison to non-irradiated samples. The differences were observed above decomposition temperature of 200°C and were non-linear with respect to radiation dose. Partial oxidation of the products during irradiation in air could be responsible for the observed differences. 相似文献
956.
957.
Frank?WendlerEmail author Gerhard?Grane? Thomas?Heinze 《Cellulose (London, England)》2005,12(4):411-422
The thermal stability of cellulose/N-methylmorpholine-N-oxide (NMMO) solutions were investigated using UV/VIS spectrometry with a temperature programming cuvette and caloric measurements
by means of the Systag calorimeter RADEX (mini-autoclave). Both analytical methods allow to characterize the influences of
stabilizers and additives. With the temporal course of the optical density, temperature and pressure thermal runaway reactions
with gas evolution and accumulation of chromophoric degradation products were recognized. Kinetic model calculations compared
with UV/VIS measurements demonstrate the existence of autocatalytic reactions in cellulose/NMMO solutions. Varying the heating
rate autocatalysis can be proved by dynamic caloric measurements as well. 相似文献
958.
This study presented results on reduction of alumina
supported chromium and platinum–chromium catalysts using temperature
programmed reduction method (TPR). It has been shown that catalysts after
earlier oxidation step but without calcinations one undergo reduction in lower
temperature in comparison to calcined only catalysts. Moreover, addition platinum
to Cr/Al2O3 catalysts also caused
decrease of reduction temperature. It has been observed that over the examined
catalysts oxidation CO to CO2 and reduction CO to CH4
occurs. However, on Pt–Cr catalysts both reactions proceed at lower
temperature compare to Cr catalysts. 相似文献
959.
960.
本文介绍一种简单、快速、灵敏、直接分析酒中游离脂肪酸的测定方法。用涂有OV-17熔融石英毛细管柱。选择游离脂肪酸质谱图中的基峰离子m/z 60进行SIM检测。定量测定了茅台酒、珍酒及鸭溪窖酒中十二种游离脂肪酸。 相似文献
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