1. It is shown that the absolute values of the coagulation thresholds of SKS-30A latexes diluted down to 0.01% correspond to the usual values for lyophobic sols. The values for NaCl are 200 times those for CaCl2, and increase with the latex concentration. The complete coagulation concentration for NaCl is 30 times that for CaCl2, and does not depend on the dilution of the latex. 2. It was shown by a nephelometric method that the volume of the primary particles formed in coagulation of the latex by sodium chloride is about 10 times the volume of the uncoagulated latex globules, irrespective of the latex concentration. 3. Consideration of the experimental data, in conjunction with facts reported in the literature, leads to the concept of two stages in the coagulation of latex by electrolytes: the first is the consequence of a decrease of the zeta potential, leading to the formation of primary particles, and the second leads to coalescence of these particles. The secondary aggregation processes can be prevented or modified by introduction of certain additives (nonelectrolytes) into the latex. 4. In additon to an explanation of the mechanism of latex coagulation by electrolytes, and a demonstration that this process can be controlled, indications are given of means of an approach to development of conditions for the production of a good blanket by coagulation of latex by sodium chloride, with a much decreased consumption of the latter.
Dilatometric, rheological, and some optical (spectrography, birefringence, light scattering) investigation methods were adopted to study gelation processes in acetyl cellulose (AC), poly(vinyl alcohol) (PVA), and iodopoly(vinyl alcohol) (IPVA) solutions in different solvents. The influence of the molecular and chemical heterogeneity of these polymers upon the gelation temperature and mechanical properties of gels is ascertained. The jumps in the volume versus temperature dependence ΔV(T) of PVA fraction solutions were discovered. The greater the molecular weight of polymer fractions the higher is the temperature of these jumps. It is established that diluted AC solutions in benzyl alcohol as well as its concentrated acetone solutions are nonhomogeneous thixotropic systems with long relaxation times. The results of investigation have been interpreted by means of the conception about gelation as the separation of fractions, which have become insoluble (under changed thermodynamic conditions), from homogeneous polymer solution. These fractions form a second amorphous phase, either as the single whole network, enveloping the solution of the other fractions by its network (gel), or as discrete aggregates (gel suspension). The structure variants, for example, partial crystallization, present the consecutive stages of a thermodynamic transition of a true solution into a non‐homogeneous colloid system.
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