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21.
Frank C. Magne Robert R. Mod Evald L. Skau 《Journal of the American Oil Chemists' Society》1961,38(6):294-296
A systematic investigation has been made of the effect of fatty acid composition on the compatibility of the corresponding
mixed morpholides as plasticizers for vinyl chloride-vinyl acetate copolymer resins. Plasticizer evaluation data were obtained
for the morpholides of lauric, palmitic, elaidic, and epoxyoleic acids and compared with the literature values for other fatty
acid morpholides and morpholide mixtures.
Ternary compatibility-composition diagrams have been constructured for the oleic-linoleic-stearic and the oleic-linoleic-palmitic
morpholide systems. These diagrams make it possible to predict what adjustment, if any, must be made in the composition of
any mixture of these fatty acids so that the corresponding morpholide mixture will be compatible. The diagrams will be useful
in selecting the most appropriate and economical fatty acid sources from which to make compatible morpholide mixtures.
Presented at the 52nd Annual Meeting, American Oil Chemists’ Society, St. Louis, Mo., May 1–3, 1961.
One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U.S.
Department of Agriculture. 相似文献
22.
A study has been made of the thermal-oxidative stability of several commercially available carbon fibers. Significant differences in the weight loss behavior were observed in air aging studies run on the bare fibers at 600°F (589 K). The stability of high temperature laminates, such as those based on NR-150 polyimide precursor solutions, was found to be directly affected by the stability of the reinforcing carbon fibers. In studies carried out to determine the reasons for carbon fiber instability, residual sodium sulfate was found to be the principle destabilizing factor. A mechanism whereby the sodium sulfate promotes the oxidation of carbon in the presence of air is proposed. 相似文献
23.
Frank N. Jones Weidian Shen Stanley M. Smith Zhihua Huang Rose A. Ryntz 《Progress in Organic Coatings》1997,34(1-4):119-129
Scanning probe microscopy (SPM) is in a period of rapid development. It shows great promise for characterizing coating surfaces. This paper describes modification of an SPM so that it can be used to mar the surfaces of coatings under controlled conditions and to characterize the mars. Mar resistance of coatings is analyzed in terms of a ‘three response, two mechanism model.' The three responses (fracture, elastic, and plastic) can be measured quantitatively using the SPM. Of the three responses, only two (fracture and plastic deformation) are marring mechanisms – elastic deformations recover instantaneously. In some cases mars resulting from plastic deformation may recover slowly with time or with immersion in water; this phenomenon is attributed to viscoelastic creep. Microhardness is also measured with the modified SPM. Some thermoset coatings appear to be substantially harder near their surfaces than in the mass of material, and such materials may respond quite differently to stress applied at different levels near the surface. This finding has important implications for all coating properties that are strongly influenced by the surface. A quantity called ‘micro mar resistance' is defined. It may be useful for comparing different coatings under specified conditions of marring. However, there can be no single quantity that expresses ‘mar resistance' of a coating under all conditions. 相似文献
24.
When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393–455 °C, pyrite (FeS2) in coal is partially converted to magnetite (Fe304). The maximum amount of Fe304 formed during the time of heating corresponds to 5–20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains. The fact that the magnetic properties of the pyrite grains are substantially increased by the magnetite crust suggests that pyrite can be separated from coal by use of a low magnetic field. In a laboratory test, 75% removal is obtained by means of a 500 Oe magnet on three samples, and 60% on a fourth sample. 相似文献
25.
Cholesterol 5α,6α-epoxide (α-epoxide) and cholesterol 5β,6β-epoxide (β-epoxide) were individually suspended in simulated gastric
juice (pH 1.2) at 37 C, and their reaction was followed by gradient high performance liquid chromatography (HPLC) with flame
ionization (FID) detection. Both epoxides reacted rapidly in the aqueous acid medium. The α-epoxide formed 6β-chlorocholestane-3β,5α-diol
(α-chlorohydrin) and 5α-cholestane-3β,5,6β-triol (triol), while the β-epoxide formed 5α-chlorocholestane-3β,6β-diol (β-chlorohydrin)
and triol. The isomeric chlorohydrins reacted further to form the triol. In mildly alkaline aqueous medium, each chlorohydrin
reverted to the epoxide from which it was formed. The data suggest that both epoxides, which have been reported to have adverse
health effects in animals, would be largely hydrolyzed in the stomach and to the triol, which also has been reported to have
biological activity. The data furher suggest that residual chlorohydrins surviving stomach residence can be expected to revert
to epoxide in the more alkaline intestinal environment. 相似文献
26.
An aerosol dynamics model, AERO2, is presented, which describes the formation of H2SO4-H2O aerosol in a smog chamber. The model is used to analyse how the uncertainties on four input parameters are propagated through an aerosol dynamics model. The input parameters are: the rate of the reaction between SO2 and OH (k1), the ratio between the nucleation rate used in AERO2 and that derived from classical nucleation theory (tn), the H2SO4 mass accommodation coefficient () and a measure of the turbulence intensity in the reactor (ke). Uncertainties for these parameters are taken from the literature. One of the results of the analysis is that AERO2 and aerosol dynamics models in general can only predict upper bounds for the total number (Ntot) and total volume (Vtot) concentrations of the particles. The uncertainties on Ntot and Vtot are mainly due to the uncertainties on k1, and tn. An uncertainty factor of 20–100 still remains when the uncertainty on k1, is reduced to ±5%. Aerosol measurements from three smog chamber experiments have therefore been used, in an attempt to reduce the uncertainty on k1 and tn. Values for k1 are obtained in the reduced range 7.8 × 10−13 to 1.0 × 10−12 cm3 s−1, which is within the range found in the literature. For tn, values in the range 104–107 are obtained, which is close to the upper bound of the range in literature. These values for tn are in marked contrast with a recent set of experiments on nucleation in H2SO4-H2O mixtures, which suggests a value for tn of at most 10−5. 相似文献
27.
A variety of crosslinked phenol-, or derivatized phenol-formaldehyde polymers have been synthesized. The phenol derivatives included o- and p-cresol, p-nonylphenol, m-pentadecylphenol, and raw and distilled cashew nutshell liquid. The derivatives were copolymerized with phenol and formaldehyde using sulfuric acid as catalyst to yield novolak-type prepolymers, which were then cured with hexamethylenetetramine. Thermogravimetric analysis was used to evaluate the thermal stability of the cured resins. It was found that the thermal stability of the resins decreased with increasing amounts of cashew nutshell liquid, with distilled cashew resins being slightly more thermally stable than raw cashew resins. The thermal stability of resins containing substituted phenols with alkyl chains was observed to increase from n-pentadecylphenol to cresol to phenol. The trend in thermal stability of the resins may be explained on the basis of alkyl groups being less thermally stable than aromatic rings. The amount of hexamethylenetetramine used to cure the prepolymers also influences the thermal stability of the resins. It appears that a level of 10 to 15% hexamethylenetetramine maximizes the thermal stability of the resin. 相似文献
28.
Barium Metaplumbate Ceramic Electrodes for Ceramic Capacitors 总被引:2,自引:0,他引:2
Frank P. Skeele Robert E. Newnham Leslie E. Cross 《Journal of the American Ceramic Society》1988,71(5):263-C
A novel approach to reduce electrode costs in ceramic capacitors is presented. Barium metaplumbate (BaPbO3 ) was fired onto sintered commercial (Ba, Sr)TiO3 disk capacitors as external electrodes. Samples were compared to disk capacitors of the same composition with electrodes made of sputtered gold and air-dried silver. The ceramic electrode led to substantial changes in the insulation resistance and dc breakdown strengths, but other properties remained the same. The feasibility of using BaPbO3 electrodes strongly depends on chemical reactions between the electrode and dielectric. 相似文献
29.
30.
Evolutionary algorithms are randomized search heuristics, which are applied to problems whose structure is not well understood, as well as to problems in combinatorial optimization. They have successfully been applied to different kinds of arc routing problems. To start the analysis of evolutionary algorithms with respect to the expected optimization time on these problems, we consider the Eulerian cycle problem. We show that a variant of the well-known (1+1) EA working on the important encoding of permutations is able to find an Eulerian tour of an Eulerian graph in expected polynomial time. Altering the operator used for mutation in the considered algorithm, the expected optimization time changes from polynomial to exponential. 相似文献