No abstract

The crystalline equilibrium diagrams were obtained for eight LDPE--n-alkane systems with the cloud point method. A point of view was formulated in which there is a major difference between crystal separation in lowmolecular-weight systems and systems containing flexible macromolecules, and it derives from differences in the essence of the phase transitions that take place in these systems.

No abstract

No abstract

A comparative study of the surface activity of different brands of oiling agents was conducted. It was found that the laminar compositional instability, manifested by the nonmonotonic dependence of the surface tension of emulsions on their concentration and~or a change in it during storage, is characteristic of all products investigated. Data indicating the characteristic nature of the dependences of the surface tension of aqueous emulsions of oiling agents on the concentration and the possibility of using them for identifying oiling agents were obtained.The oiling agents used in the production and processing of chemical fibres and filaments are multicomponent colloidal systems [ 1-4] which tend toward laminar compositional inhomogeneity while retaining aggregate stability judging by some data [5].The degree to which the surface tension of aqueous emulsions of such agents, measured by the technically simple Wilhelmy plate method [6] can reflect the appearance of compositional inhomogeneity in them is studied in the present article. We departed from the totally obvious (from a colloid chemistry point of view [7]) hypothesis that when the composition of the surface layer of an aqueous solution of a mixture ofsurfactants (SF) changes because of a change in the ratio of the concentrations of the components, the character of the concentration and time curves of the surface tension (cy) of solutions of such SF should differ from the curves for solutions of single-component SF.The experiments were conducted at a temperature of293.0• K on a setup based on a VLR-200 balance. The surface of the liquid sample in a small working beaker 4-10 -2 m in diameter and thermostated cell similar to the one used in [8] was moved relative to the plate by a reversible electric motor with a multistep reduction gear that made it possible to vary the velocity (t)) from 0.33 to 90 mm.min -1 (in this study, all measurements were made at 1) = 4 mm.min-1).Another feature of the design of the setup consists of using a miniature magnetic stirrer as the mobile table to which the thermostated cell is attached, as this allows homogenizing (if necessary) the emulsion directly during the experiment.To decrease the probability of accumulation of static electricity in the system as a result of friction of the heat carrier against the wall of the cell, a 1 N aqueous solution of NaC1 was used as the heat carrier and the cell was grounded by a band wrapped around it.Two plates were used: a platinum plate with a working edge perimeter ofL = 4.15-10 -2 m (length of 2.04.10 -2, width of 3.4.10 -4 m) and a poly(ethylene terephthalate) (PETP) plate with L = 4.04-10 -2 m (length of 2.10 -2, width of 2.10-4 m). Force (F) of the plate's breaking away from the surface of the liquid was established as in the initial version of the Wilhelmy method. Figure 1 shows that in using both the platinum and the polymer plates, the curve of the force of their breaking from the surface of the pure liquids was rigorously linear in accordance with the equation in [6]:F= Lcy.The...