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The addition of ZnO, depleted in the Zn-64 isotope, to the water of boiling water nuclear reactors lessens the accumulation of Co-60 on the reactor interior surfaces, reduces radioactive wastes and increases the reactor service-life because of the inhibitory action of zinc on inter-granular stress corrosion cracking. To the same effect depleted zinc in the form of acetate dihydrate is used in pressurized water reactors. Gas centrifuge isotope separation method is applied for production of depleted zinc on the industrial scale. More than 20 years of depleted zinc application history demonstrates its benefits for reduction of NPP personnel radiation exposure and combating construction materials corrosion.

This paper presents the results from an experimental laboratory investigation studying the volumetric and unidirectional freezing of oil-polluted soils. The experiments are a part of a larger laboratory programme where the objective is to understand how oil pollution affects the phase transition velocity and how the phase transition is dependent on the oil/soil structure, the temperature near the points of crystallisation and the orientation of the ice crystals.

Conditions have been found for determining by gel permeation chromatography the molecular mass distribution of polyamide-66 in the form of the corresponding fluoroacetyl derivative. The course of the reaction between polyamide-66 and trifluoracetanhydride was followed by IR spectroscopy. Variation in the molecular mass distribution of PA-66 samples of different molecular mass treated at elevated temperatures either individually or in mixture was studied in order to evaluate possible exchange reactions.

The hydrodynamic characteristics of an aromatic polyamide based on 3,3′-dihydroxy-4,4′-diaminodiphenylmethane and isophthalyl chloride were studied by viscometric and sedimentation rate methods. The constants for equations relating intrinsic viscosity and sedimentation constant with MM were determined. The unperturbed dimensions of macromolecules, separation between chain ends with free rotation around valence bonds, the Kuhn segment and the equilibrium flexibility parameter were determined by known extrapolation methods. This polyamide belongs to the class of flexible polymers.

Several techniques for the GPC analysis of PA-66 are compared, and a new eluent for room temperature chromatography is proposed consisting of a mixture of m -cresol and chloroform in 3 : 7 ratio by volume, which can be used to determine the MMD of aliphatic PA.

The characteristics of the MMD of polycarbonate siloxanes of varied composition have been investigated. Using the results of GPC and viscometry the authors have determined the values of the constants in the Mark-Kuhn-Houwink equation for the copolymer in THF. The constants change little with the composition of the copolymer within the limits studied. Comparison of the results of determination of the MM and MMD of the samples using different independent methods reveals good agreement of the values obtained. The parameters of the equilibrium rigidity of the macromolecules are evaluated.

The theoretical concept of polymer chromatography under “critical conditions” that allows the separation of oligomer samples by functional-type distribution is discussed. Calculation of the optimum conditions for the gradient separation of such mixtures for simultaneous determination of the molecular mass distribution and functional-type distribution is also considered. To ensure a correct evaluation of the molecular mass distribution of the polymer products, a precise method of exclusion chromatography involving an internal standard and correction of the calibration equation according to a characterized sample is suggested. Double detection, with a UV detector and a refractometer, makes it possible to estimate the role of low-molecular-weight fractions of polysulphone during heat-treatment, which influences the optical characteristics of polymers.

Functional type separation of hydroxyl-containing poly(butylen terephtalates) by liquid chromatography of molecules in “critical conditions” was investigated. Under such conditions the change in the free energy, ΔF, of a homogeneous macromolecule equals zero when entering a pore, irrespective of its length; in this case the chromatogram obtained is not complicated by the separation of the molecules in terms of sizes, and contains information only on the types of functionality. The critical conditions of investigation have been determined on silica in a heptane-tetrahydrofuran (THF) mixture.

A study was made of the solubilization of styrene and chloroprene in aqueous solutions of cetyl alcohols with varying degrees of hydroxyethylation, and the kinetic principles of the polymerization of these monomers were investigated. The results show the dissimilarity of the mechanism of latex particle formation in the presence of non-ionic emulsifiers compared with analogous processes where ionogen emulsifiers are used.

A precision GPC technique has been devised and the values of them mean MW and MWD of polycarbonates obtained in different conditions of synthesis evaluated. Change in the technological parameters of the stage of phosgenation practically does not affect the polydispersity of the polycarbonate. The presence of 5–10% low molecular weight fractions in the polymer does not worsen its optical and rheological properties.

Adsorption chromatography and GPC under isocratic and gradient conditions were used to investigate MMD and distribution according to types of functionality of oligomers of polybutylene terephalate-products of re-esterification of dimethylterephthalate with 1,4-butanediol. It was shown that a number of compounds are present in the mixture, including dimethylterephthalate, mono- and dihydroxybutylterephthalates and oligobutylene terephthalates. Results of chromatographic analysis were confirmed by direct identification of components of the mixture analysed using mass-spectrometry of field desorption.

It is shown that the thermostability of an aromatic polysulphone determined from change in the optical properties and oxygen uptake largerly depends on the character of the MD. The high molecular weight fractions of polysulphone are unstable in the individual state although their thermostability synergically rises in presence of low molecular weight fractions. The influence of the MD on the thermostability of a polysulphone is also related to change in the content of the terminal hydroxyl groups.

The stability of polysulphone during high-temperature oxidation has been determined from the intensity of yellowing and from the absorption of oxygen. It was found that the stability decreases for high values of MW, and as the number of OH endgroups rises. The oxidation of polysulphone is accompanied by crosslinking and degradation processes. It was found by GPC analysis that degradation predominates in high-molecular weight samples, and that OH endgroups accelerate branching of the macromolecules. Yellowing of the oxidized polysulphone is related to products of structural transformations of the polymer; colouration is most marked for branched structures formed with the participation of OH endgroups.

The monomer (3,3′,4,4′-benzaphenone tetracarboxylic dianhydride and 4,4′-diphenyl-methane diisocyanate) consumption and n -mer accumulation were quantitatively studied using gel-permeation chromatography (GPC). Mathematical models were derived by taking account of the effect of oligomer chain length on chain end group reactivity. By using the data on change in reactant and product concentration, the kinetic parameters of the models were calculated. Some conclusions were made on the mechanism of the process.