Gel curve

Fig. 5.8 Adsorption isotherms at 25°C of benzene and cyclohexane on a mesoporous silica gel. Curve (A), benzene curve (B), cyclohexane. Solid symbols denote desorption.

The gel curves (Figures 5-11) were obtained by measuring the viscosity of hemicellulose suspensions while the temperature was increased at a rate of 1 °C/minute to approximately 90 °C. The hemicellulose mixture was then cooled at the same rate. 

An increase in pH of the hemicellulose solution thus clearly decreases the gelling temperature of the hemicellulose suspension. The gel curves of the... 

Figure 5. Gel curves of hemicellulose (32% ash) suspensions (15% solids) (J). The pH of the hemicellulose was adjusted to the indicated values before drying and grinding.

In Figure 9, the gel curves of purified hemicellulose treated with borax and acid to obtain different pH s before drying are illustrated. These curves are almost identical over a wide pH range. The main difference is the temperature where the viscosity of the suspension starts to increase. This temperature increases with a decrease in pH. The temperature of complete gelling, as indicated by the maximum temperature during the heating stage, increases from 72 °C at pH 9 to 78 °C at pH 5. 

Figure 8. Gel curves of hemicellulose suspensions (12.5% solids) containing different quantities of ash (>/). Each hemicellulose was treated with 2% borax and diluted with sulfuric acid to pH 7.5 to 8.0 before drying and ball-milling.

Figure 9. TG curves of desorption for silica gel (curves 1,2,3) and aluminium oxide (curve 4). 1 - acetone, 2 - carbon tetrachloride, 3 - n-butanol, 4 - benzene.

Fio. 7. Nitrobenzene. Curve 1 vapor D scale x 10) curve 2 vapor adsorbed on a disk of pressed silica gel curve 3 after evacuation. From Okuda (55). 

Fio. 8. -Trinitrobenzene. Curve 1 grinded with MgO powder in tur curve 2 grinded with silica gel curve 3 dissolved in alkaline ethanol. Diffuse reflection spectra. From Kortiim et al. (62). The scale on the right is for the dashed curve. 

Fig. 11. Aniline vapor adsorbed in vacuo. Curve 1 on silica gel curve 2 on alumina gel curve 3 on silica-alumina gel (50 50) curve 4 on Na-silica-alumina gel curve 5 on Li-silica-alumina gel. Diffuse reflection spectra, from Kotov and Terenin (27).

In Fig. 12 (curves 1 and 2) the double peaked absorption maximum, 520 and 560 m a is shown, characteristic of the positive ion-radical of dimethyl-p-phenylene diamine (MejN—Ph—NHa)t (77), which was here obtained by adsorption of the vapor under high vacuum conditions (27, 78). The same interpretation is given to the absorption maximum 850 m/a for benzidine vapor, adsorbed on silica-alumina gel (curves 3 and 4), which does not appear on silica gel. The band of the benzidine ion-radical, obtained by photoionization in the rigid EPA solvent at - 180°C is situated at 885 m/x (76). The accompanying bands 760 and 450 seem to be intimately connected with that at 850 m/a. 

The chemical and electrical components of the electrochemical free energy (Gel = G + mF( ) as discussed in Chapter 2) also are represented in Fig. 3.6. The shape of the electrical-component curve is defined by a, the fractional change in the potential as a function of position a, the transfer coefficient, is the fractional change at the maximum of the Gel curve. G and G el are the GFE and the electrochemical free energy, respectively, of the ion at the position of the maximum of these energies on traversing the interface. Ions in this state are frequently referred to as... 

Fm. 30. Absorption spectrum of triphenylmethane curve A, in ethanol solution curve B, adsorbed on silica gel curve C, B after 4-hr evacuation at 100°C (29). 

Fig. 33. Triphenylcarbonium ion formation with supported Lewis and Bronsted acids curve A, 3CH adsorbed on silica gel curve B-l, 500 mm HF added at 26°C curve B-2, heated 115°C 4 hr curve C, (/>3CH adsorbed on silica gel and BFS added at 26°C curve D, < 3CH adsorbed on silica-alumina curve E, < aCOH adsorbed on silica gel and HF added at 26°C.

Figure 6.5 Generic resist gel curve, showing the gel point exposure, Eq.

Reiser and E. Ktts, Cbaracteristic curve of crossUnking photoresists, Photogr. Sci. Eng. 20, 225 (1976) J. Pinter, Z. Haniotis, K. Meier, and H. Zweifel, A numerical method for calculation of gel point exposure energies from experimental gel curves Photo cross linking of unsensitized poly[vinyl 3 (3,4 dihydro 1,2 naphthalene dicarboxylic acid imidyl) proprionate], J. Imaging Sci. 30, 259 (1986). 

Equation (9.B.3) represents the Charlesby-Pinner s equation [109], which is widely employed to analyze the gel curve. 

FIGURE 1.300 29Si nmR spectrum of TES sol-gel (curve 1) and spectrum with proton decoupling (curve 2). (Adapted from Spectrochim. Acta Part A., 70, Li and Ba, Spectroscopic studies of triethoxysilane sol-gel and coating process, 1013-1019, 2008. Copyright 2008, with permission from Elsevier.)... 

FIGURE 11.11. Adiabatic desorption equilibrium curves for (a) 4A sieve and (6) silica gel. Curves arc calculated for a uniformly saturated bed at 25 C at the indicated humidity, assuming bone-dry purge gas at the specified temperature. The 25 isotherm is shown as---------, representa-... 

Another interesting result from model simulation involves the importance of the diffusivity possible in the gel phase. In practice the diffusivity in the gel is mostly a function of water content and crosslink density. However, any experiment designed to measure the variation of reaction in the gel as a function of diffusivity would be confounded by the occurrence of numerous other changes. Figure 5 shows the calculated effect of diffusivity in two gels, curve A representing PHEMA-VP and curve B, PHEMA. 

Figure 6.2.6. Dependence of equilibrium swelling of PBU on the q>2 value for DEP in the liquid phase (curves 1 and 2) and the < >2 value inside the swollen gel (curves 1 and 2 ) in the mixtures l,l -hexane(l)-DBM(2), 2,2 - hexane(l)-DBP(2).

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