The aim of this paper was to determine the influence of a great number of successive rhombic monoclinic crystal transformations on the ammonium nitrate crystal transformation energies. The energies of ammonium nitrate crystal transformations from rhombic into monoclinic, from monoclinic into trigonal and from trigonal into cubic were observed as functions of the number of previous crystal transformations and the moisture content.The phase transformations of ammonium nitrate have been extensively investigated by DTA, DSC and dilatometry [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. The structures of the phases have also been investigated [16][17][18][19][20][21][22]. Open questions remain as regards the behaviour of ammonium nitrate in the temperature range from 30 ~ to about 60 ~ and the influence of repetition of heating and cooling cycles through the NH4NOa(IV) .-~--NH4NOa(III) phase transformation point [1,17,19,21].The purpose of the present work was to investigate the changes in temperature and energy of the rhombic into monoclinic (IV ~III), monoclinic into trigonal (III ~II) and trigonal into cubic (II ~I) crystal transformations for prilled ammonium nitrate samples after 5,10,15,20, 35 and 50 rhombic-monoclinic crystal transformations. The ammonium nitrate samples contained from 0.01 to 1.21% (mass) of moisture, and the influence of the moisture content on the crystal transformation energies was also investigated.
Surfactant mixtures are very often used in various cosmetic and pharmaceutical products because they commonly act in synergism and provide more favorable properties than a single surfactant. Simultaneously, the presence of polymers in mixtures of surfactants may lead to molecular interactions and thereby affecting product stability and activity. For these reasons, it is very important to determine the influence of surfactant interactions on micellization and mixed micellization, as well as polymer-surfactant mixed micelles interactions. In this study, the self-aggregation of nonionic surfactants, polysorbate 20 (Tween 20), polyoxyethylene octylphenyl ether (Triton X100) and polyoxyethylene-polyoxypropylene block copolymer (Pluronic F68), with an ionic surfactant, sodium dodecyl sulfate, was examined in aqueous solution at 40 °C using a conductometric titration method. It was found that the concentration region for mixed micelle formation depends on the characteristics of the nonionic surfactant and its concentration. The formation of mixed micelles of surfactants in the presence of a nonionic polymer, hydroxypropylmethyl cellulose, and their binding to the hydrophobic sites of the polymer were also investigated. An analysis of obtained results indicated to different kinds of interactions in the investigated systems, which are crucial for their application.
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