Gelation studies

Kinetics of Gelation Studied by Dynamic Rheological Measurements... 

None of the Cr(III) products from Equations 6 or 7 are effective crosslinkers since a chromic aqua ion must be hydrolyzed first to form olated Cr to become reactive. Colloidal and solid chromium hydroxides react very slowly with ligands. In many gelation studies, this critical condition was not controlled. Therefore, both slow gelation times and low Cr(VI) Cr(III) conversion at high chromate and reductant concentrations were reported (9,10). 

Richter, S., Boyko, V, Matzker, R, and Schroter, K. 2004. Gelation studies Comparison of the critical exponents obtained by dynamic light scattering and rheology, 2(a)—N thermoreversible gelling... 

Pouxviel, J.C., Boilot, J.R, Danger, A., and Wright, A., Gelation study of aluminosilicates by small-angle neutron scattering, J. Non-Crystl. Solids, 103, 331, 1988. 

For the gelation studies, standard PF resin conditions were used. The effects of the ratio of reactive sites (phenol/formaldehyde), the average functionality of the phenolic system, and the amount of monofunctional phenolics were studied. Since the solids content and pH of all systems were the same, solution viscosity was used to monitor the system s average molecular weight. 

Understanding the rheology of the fiber-spinning dope solutions is important to enable the fabrication of the polyaniline fibers with reproducible electrical and mechanical properties. In our studies, a Brookfield RVDV-III cone and plate rheometer was used to measure the viscosity of the concentrated EB solutions. The gelation studies of these solutions were conducted at 25°C and a constant shear rate of 0.8 using cone spindle (CP-52) with a semivertical cone angle of 87°. Figure 2.10 illustrates the viscosity... 

Phase Separation and Gelation Studies. A phase diagram of linear poly(ethylene oxide) (LPEO) and divinyl benzene (DVB) cross-linked poly(methyl methacrylate) as a function of polymerization of the latter was also researched hy duPrez and co-workers (49) (Fig. 11). The temperature of measurement was also a variable, but the curve separating the one-phased system from the two-phased system did not change much in the narrow temperature range covered. 

In our laboratory, we have recently conducted gelation studies of silica nanopardcles in microgravity during the STS-95 space shuttle mission (28). Stable silica nanoparticle dispersions may be form either by polymerization of silicic acids in an aqueous system or through hydrolysis and condensation of silicon alkoxides (the sol-gel or Stober route). Comparison of small-angle x-ray scattering (SAXS) measurements of Ludox, a commercial aqueous silicate with acid- and base-catalyzed alkoxides shows that only aqueous silicate sols are uniform, whereas alkoxides generate fractal particles. As Brinker and Scherer point out (29), these results illustrate that sols derived from aqueous silicates are... 

Richter S (2007) Recent gelation studies on irreversible and reversible systems with dynamic light scattering and rheology. A concise summary. Macromol Chem Phys 208(14) 1495-1502... 

To illustrate the proposed methodology, a gelation study of medicine was conducted in which two control factors of PEO (xi) and PEG (X2) were chosen. The time-oriented responses are gelation measurements of medicine collected from 0.5 hour to 5 hour (as described in Table 1). At each time, there are 6 experimental runs and four replications for each experimental run (as described in Table 2). In the Error Reference source not found, below, the data yi is the column of mean values and Si is the column of variance values of experimental runs. The main purpose of study is finding the optimal setting of control factors so that the mean responses y (gelation measurements) are near the targets and the variances s can be reduced as much as possible. For somewhat reasons, the experimental data cannot be published. 

Fig. 1 Mean responses and targets versus time of gelation study...

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