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91.
92.
The effect of the micelles on the dynamic surface tension of micellar surfactant solutions is studied experimentally by means of the maximum bubble pressure method. Different frequencies of bubbling ranging approximately between 1 and 30 s–1 are applied. The time dependence of the surface tension is calculated using a dead time correction. Water solutions of two types of surfactants with different concentrations are investigated: sodium dodecyl sulfate and nonylphenol polyglycol ether. The surface tension relaxes more quickly in the presence of micelles. The characteristic times of relaxation of the surface tension seem to be in the millisecond range. The time constants observed experimentally are explained in terms of the theory of surfactant diffusion affected by micellization kinetics. 相似文献
93.
For many applications poly(styrene) must
be treated to reduce its flammability. This is usually done by incorporating
a flame retardant additive, usually an organohalogen compound, into the formulation
as the polymer is being processed. A potentially very efficient way of introducing
flame retardance would be to incorporate a suitable structural unit directly
into the polymer. This can be done by using 2,4,4,5,5-pentaphenyl-1,3,2-dioxaphospholane
as an initiator for styrene polymerization. The strained carbon–carbon
bond of the phospholane undergoes homolysis at moderate temperatures to generate
a diradical which initiates polymerization. The resulting polymer contains
an O–P–O unit in the mainchain. Thermogravimetry indicates that
the thermal stability of the polymer is quite comparable to that of poly(styrene)
generated by conventional methods. 相似文献
94.
A novel extraction method, namely dynamic ultrasound-assisted extraction, is investigated. This technique is efficient with respect to both time and solvent consumption because it utilizes ultrasonic energy in dynamic mode during extraction. Polyphenols (chlorogenic acid, esculetin, rutin, scopoletin, and quercitrin) are extracted from a tobacco (Nicotina tobaccum L.) sample for 10 min with 6 mL of solvent. Fresh solvent is continuously pumped through the sample, with which the analytes can be rapidly extracted, and the possibility of degradation efficiently avoided. Methanol involving 0.5% w/v ascorbic acid was used as extraction solvent; optimal flow rate and extraction time were investigated. The extract was cleaned up by C18 disposable cartridge. The spiked and nonspiked tobacco samples were used for the evaluation of the proposed method. Recoveries obtained were varied from 96 to 108% and RSDs from 2.0 to 4.6%. This extraction technique was revealed to recover larger amounts of polyphenols from tobacco, compared to the static ultrasound-assisted extraction method. 相似文献
95.
V. A. Drebushchak L. N. Mylnikova T. N. Drebushchak V. V. Boldyrev 《Journal of Thermal Analysis and Calorimetry》2005,82(3):617-626
Summary Ancient ceramic samples (single fragments and different parts of pots, unbroken and repaired; total about 180 samples) dated
from the transitional period of late Bronze to early Iron Age (VIII-VI centuries BC) and early Iron Age (VII-IV centuries
BC) were investigated by thermal analysis, X-ray powder diffraction, petrography, and scanning electron microscopy equipped
with the energy-dispersive X-ray analyzer. In addition to that, to identify the clay sources for the ceramic manufacturing,
about 15 samples of clays and soils found near archeological digs and taken from the mineralogical museum were investigated.
We found out that the calcite content of ceramics is a very informative parameter for the identification of the clay source
for the pottery manufactured at low technological level (low-temperature firing). 相似文献
96.
A. Hamou C Devallencourt F. Burel J. M. Saiter M. Belbachir 《Journal of Thermal Analysis and Calorimetry》1998,52(3):697-703
The thermal stability of p-cresol novolac resin was studied by means of DSC, X-ray diffraction, thermogravimetry and SEC investigations.
After 30 thermal cycles in which the same sample was heated, cooled and heated again, without attainment of the temperature
of degradation at any time in the experiment, important structural modifications are observed. At the end of the experiments,
the resin, which is initially highly crystalline, exhibits all the characteristics of a semi-crystalline material.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
97.
草酸镁二水合物的非等温热分解动力学 总被引:1,自引:0,他引:1
The thermal decomposition of the magnesium oxalate dihydrate in a static air atmosphere was investigated by TG-DTG techniques. The intermediate and residue of each decomposition were identified from their TG curve. The kinetic triplet, the activation energy E, the pre-exponential factor A and the mechanism functionsf(a) were obtained from analysis of the TG-DTG curves of thermal decomposition of the first stage and the second stage by the Popesou method and the Flynn-Wall-Ozawa method. 相似文献
98.
指出了当前流行的差示扫描量热法DSC单峰法测样品纯度所基于的假定有一些不确切的地方,并用计算机动态摸拟了DSC实验过程,结果证实了本文的论断。 相似文献
99.
Production of micron-sized monodispersed composite polymer particles by seeded polymerization utilizing the dynamic swelling method 总被引:1,自引:0,他引:1
In order to develop the seeded polymerization technique utilizing the dynamic swelling method (DSM) proposed by authors for
the production of micron-sized mono-dispersed “composite” polymer particles consisting of two kinds of polymers, the seeded
polymerization for the dispersion of ethyl methacry-late (EMA)-swollen PS particles prepared utilizing DSM was carried out.
Monodispersed PS/poly(ethyl methacrylate) (PEMA) composite particles having 7 μm in diameter were produced by the addition
of NaCl to lower the solubility of EMA in medium and by the addition of CuCl2 as a water-soluble inhibitor to depress the by-production of submicron-sized PEMA particles.
Received: 16 July 1996 Accepted: 10 October 1996 相似文献
100.
M. Baru A. Danilov I. Vagenina E. Gorbunova S. Moshnikov L. Mustaeva V. Cherskii 《Chromatographia》1997,45(1):351-354
Summary The design of new dynamic, axial-compression columns with a system for continous packed bed adjustment and monitoring of the
floating adapter position is described. The columns are meant for liquid chromatography at low pressures (up to 8 bar) in
aqueous and organic media with stationary phases of all types. The columns have adapter position pickups for continuous automatic
monitoring of the bed height (original “swellographic” monitoring). The column described with gas pressurisation was tested
with soft Sephadex G-10 and G-25. In spite of the reduction in external porosity there was no dramatic increase in back-pressure.
The column proved to provide long-term stability of the packed bed and improvement in resolution.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献