Polarization-optical methods of investigating structure-formation kinetics in polymer systems

Conclusions Contemporary rapid optical methods have been developed for investigating structural transformations in the precipitation of polymers from solutions, structure study and monitoring during thermal and deformational actions on polymer solutions, films, and fibres.Application of these methods makes it possible to determine basic structural parameters — anisotropy, orientation, size and morphology of supermolecular structures; these characterize operational properties of fibres and films.The experimental assemblies devised on the basis of optical methods with photographic or photoelectric recording of the transmitted and scattered light have improved metrological characteristics; they are universal, and are used to monitor fast-occurring processes of structure-formation in spinning fibres and films without interference into the investigated system.Translated from Khimicheskie Volokna, No. 4, pp. 6–10, July–August, 1986.     

An acoustical method of investigating plasticization of hydrocellulose films

Conclusions The effect of various plasticizers on the propagation velocity and damping coefficient of ultrasonic waves has been studied in model specimens of hydrocellulose films.It has been shown that the damping coefficient of ultrasonic waves is a characteristic more sensitive to the content of plasticizer and water in a film than the rate of propagation of ultrasonic waves.Translated from Khimicheskie Volokna, No. 1, pp. 34–35, January–February, 1985.     

A method of investigating the structure-formation process of unoriented polyacrylonitrile specimens

Conclusions A method has been proposed which permits one to quickly evaluate the effect of wet spinning conditions on the structure of an unoriented polyacrylonitrile specimen.This method is based on spinning a spinning composition through a macro-hole and preparing a strand having a diameter of several millimeters.The structure of the strand is easily characterized by traditional methods: from geometric density, specific fraction of voids, magnitude of the shell and core, and so on.Translated from Khimicheskie Volokna, No. 2, pp. 31–32, March–April, 1986.     

A new method for investigating cement hydration by radioactive indicators

A new method for investigating the evolution of the hardened cement paste structure is proposed, based on the application of radon as a radioactive indicator. The application of this Radiometric Emanation Method (REM) enabled us to follow continuously changes in the cement paste structure during setting and hardening at the required temperature and humidity. Comparison of the REM results with those obtained by commonly used methods showed that REM affords new insights into the evolution of the cement paste structure. Changes in the area and microporosity of the cement paste samples can be advantageously investigated by REM.     

表面活性剂胶团水溶液性质的黏度研究方法

综合归纳散见于众多文献中的关于表面活性剂溶液性质与分子聚集体结构的实验研究方法,并将分篇发表。在此篇中介绍了表面活性剂胶团水溶液性质的黏度研究方法,涉及特性黏度[η]、Huggins常数KH、Kramer常数Kk、胶团表面水化度W、胶团引流体力学半径Rx以及胶团球形形状和尺寸分散性的判定等。     

A novel method for investigating electrical breakdown enhancement by nm-sized features

Electrical transport studies across nm-thick dielectric films can be complicated, and datasets compromised, by local electrical breakdown enhanced by nm-sized features. To avoid this problem we need to know the minimal voltage that causes the enhanced electrical breakdown, a task that usually requires numerous measurements and simulation of which is not trivial. Here we describe and use a model system, using a "floating" gold pad to contact Au nanoparticles, NPs, to simultaneously measure numerous junctions with high aspect ratio NP contacts, with a dielectric film, thus revealing the lowest electrical breakdown voltage of a specific dielectric-nanocontact combination. For a 48 ± 1.5 ? SiO(2) layer and a ～7 ? monolayer of organic molecules (to link the Au NPs) we show how the breakdown voltage decreases from 4.5 ± 0.4 V for a flat contact, to 2.4 ± 0.4 V if 5 nm Au NPs are introduced on the surface. The fact that larger Au NPs on the surface do not necessarily result in significantly higher breakdown voltages illustrates the need for combining experiments with model calculations. This combination shows two opposite effects of increasing the particle size, i.e., increase in defect density in the insulator and decrease in electric field strength. Understanding the process then explains why these systems are vulnerable to electrical breakdown as a result of spikes in regular electrical grids. Finally we use XPS-based chemically resolved electrical measurements to confirm that breakdown occurs indeed right below the nm-sized features.     

A new method for investigating the mechanism of initiation of radical polymerization

Summary The mechanism of initiation of polymerization of methyl acrylate by di-t-butyl peroxalate at 60°C, has been investigated using 2,2,6,6-tetramethylpiperidine-1-oxyl as a radical trapping agent and isolation of the resulting products. The following processes were identified: Tail addition of t-butoxy radicals to monomer, hydrogen abstraction from the methyl group of the monomer and fragmentation of the t-butoxy radicals to methyl radicals followed by tail addition of these to the methyl acrylate.     

Problems and prospects of investigating the formation and evolution of agglomerates by the sampling method

Problems related to the interpretation of information obtained from an analysis of collected particles of condensed combustion products of aluminized propellants are considered. It is shown that the difficulties that arise are due to three main factors: the complex statistical character of the combustion of heterogeneous propellants, which results in formation of agglomerates with a substantially polydisperse distribution in size and different (even for identical size) structure, the features of burnout of the agglomerates related to the accumulation of oxide on the burning particle, and the specific character of the motion of burning agglomerates in the gas flow. An experimental approach is proposed that makes it possible to eliminate the polydispersity of the agglomerates and uncertainty in the parameters of the gaseous products flowing away from the burning surface. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 1, pp. 161–172, January-February, 2000. This work was supported by INTAS (Grant No. 93-2560 ext).     

有机硅废触体的综合利用

介绍了合成甲基氯硅烷的废触体的主要利用方法——氧化法、深度转化法、？台炼法、去活性法等，并对国内废触体的综合利用提出了建议。     

Use of electroultrafiltration (EUF) method for investigating the behaviour of phosphate fertilizers in tropical soils

The solubility of superphosphate and rock phosphate was studied in six soils differing widely in pH, clay content, and type of clay minerals. Soils were incubated with increasing amounts of phosphate fertilizer for 1, 4, 12, and 24 weeks at 60% maximum water capacity and then extracted by means of electroultrafiltration (EUF). In the acid soils (pH-H₂ O: 4.3 to 5.6) the phosphate quantities extracted did not differ much between fertilizer types. In the neutral soils (pH-H₂ O: 6.6 to 6.9) 2 to 10 times as much was extracted from the superphosphate treatments as from the rock phosphate treatments. A fractionated EUF extraction (change of extraction time and voltage) showed that in the acid soils, rock phosphate was more soluble than superphosphate, but in neutral soils the opposite was true. In five of the six soils investigated the solubility of superphosphate declined during an incubation period of 24 weeks, whereas the solubility of rock phosphate showed no clear trend in relation to the time of incubation.

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Zusammenfassung Die Lölichkeit von Superphosphat und Rohphosphat wurde in 6 Böden untersucht, die sich beachtlich in ihrem pH-Wert, in ihrem Tongehalt und in ihren Tonmineraltypen unterschieden. Die Böden wurden mit steigenden Phosphatmengen für die Dauer von 1, 4, 12, und 24 Wochen bei 60% der maximalen Wasserkapazität inkubiert und dann mittels Elektroultrafiltration (EUF) extrahiert. In den sauren Böden (pH-H₂O): 4.3 bis 5.6) unterschieden sich die Phosphatmengen nicht wesentlich, die von den beiden Phosphatdüngemitteln extrahiert wurden. In den neutralen Böden (pH-H₂ O: 6.6 bis 6.9) wurde von den Superphosphatvarianten 2 bis 10 fach mehr Phosphat extrahiert als von den Rohphosphatvarianten. Eine fractionierte EUF-Extraktion (Änderung der Desorptionszeit und der Spannung) zeigte, daß in den sauren Böden das Rohphosphat besser löslich war als das Superphosphat; in den neutralen Böden wurde die umgekehrte Beziehung gefunden. In 5 von den 6 untersuchten Böden nahm die Löslichkeit des Superphosphates im Verlaufe der 24 wöchigen Inkubationsdauer ab. Die Löslichkeit des Rohphosphates zeigte keinen klaren Trend in Abhängigkeit von der Inkubationsdauer.

     

Damage tolerance in graphite-epoxy composite: Comprehensive monitoring method

A failure model is proposed to calculate the minimum expected lifetime of a graphite-epoxy structure under cyclic loading conditions. The theoretical approach is based on the statistical theory of strength and the mechanical redistribution of stresses between piles of a damaged laminate. The use of the acoustic emission technique has permitted the development of internal damage to be monitored during cyclic loading of unidirectional laminates. The experimental results indicate that the composite can withstand greater damage at low level cyclic loading than observed during monotonic loading to failure. The theoretical modeling under development aims at predicting this behavior.     

Photoacoustic methods of investigating fibre materials

The possibility of measuring the mechanical, particularly the elastic, properties of fibre materials by a photoacoustic method with a sufficient degree of accuracy was investigated. Thin monofilaments based on polymers with different macromolecular chain rigidity were investigated. Moscow State Textile University; All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated fromKhimicheskie Volokna, No. 6, pp. 54–57, November–December, 1999.