WSEAS Transactions on Heat and Mass Transfer
Print ISSN: 1790-5044, E-ISSN: 2224-3461
Volume 13, 2018
Investigation of the Sol-Gel Transition by Rheological Methods
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Abstract: In this paper the rheological study of gelation processes were carried out. Developed measurement complex allows obtaining rheological kinetic curves, from the beginning of sol-gel transition until complete conversion of the sol into a gel. Critical shear stresses in a wide range were measured. It showed that the starting sol is a Newtonian liquid, and after the beginning of gelation process is converted into a Bingham body, and has the character of the phase transition of the 2nd kind. Using the developed device has allowed to establish the form of the initial part of rheological curve and develop the correct method for determining the gelation time. New phenomenon was discovered which is that the kinetic curves in coordinates of Avrami-Erofeeva-Bogolubov’s equation have an inflection point that divides the kinetic curve into two parts initial and final. Numerical treatment of rheological curves showed that the constant in this equation is independent of temperature and is the same as for the initial and final part of the kinetic curve. It depends only on the chemical nature of the reacting system. It is shown that for the initial part of the rheological curves, the value of the power index in the in this model amounted n = 23.4 ± 2.8 and in contrast to the final part of rheological curve does not depend on temperature. The observed behavior of the kinetic curves due to the change process and the mechanism of reducing the number of possible directions of fractal aggregates growth.
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Keywords: Sol-gel process, Rheology, Non-Newtonian fluid, Avrami-Erofeev-Bogolubov’s equation, Phase transition of the 2nd kind
Pages: 66-75
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 13, 2018, Art. #6