Swelling efficiency

If the modification imparts dimensional stability to the wood, the difference between the water-saturated and oven-dry volume of the wood sample is reduced, resulting in a lower value for S. The increase in dimensional stability can then be evaluated in terms of an anti-swelling efficiency (ASE) ... 

Figure 3.7 The relationship between anti-swelling efficiency (AST %) and WPG for a variety of linear chain anhydrides (from data of Hill and Jones, 1996a).

Fig. 37. Swelling efficiency and free volume estimation in well-cured Fi-berite 934 network epoxies, as affected by sub-Tf annealing. Percent swelling is plotted on the ordinate axis while percent of moisture uptake is plotted on the abscissa...

Earlier we reported that physical aging affects the "swelling efficiency" and diffusivity of epoxy as moisture is transported into the network ( ). In conjunction with this earlier communication ( ), we can now summarize the findings for interactions between moisture and aging epoxies ... 

As epoxies denslfy, the "swelling efficiency" (6,10) of aged epoxy Is Increased. 

Table 12-4. Data on Hydrogen solubility, swelling efficiency, and rate of reduction of acrylamide in various solvents.

The reaction of (3-propiolactone with fiber can be catalyzed by acids or bases to yield two different products. Treated wood in acidic conditions with 30% WPG resulted in good decay resistance and anti swelling efficiency (ASE) of 60%. Nevertheless a strong degradation of wood has been observed [40]. 

Concerning possible applications, the proposed uses are still mainly based on the hydrogel character of ESA films, that is, on their tendency to swell efficiently in aqueous media without dissolution. As already discussed in Section IX up to the year 1999, such potential applications comprise biocompatible and nonfouling coatings [368,447,694,801,804-819], biodegradable coatings [774,814,820], enzyme immobilization or encapsulation [403,563,800,821-827], cell encapsulation... 

Fig. 2.2 Swelling behavior of Hercules 3501 epoxy resin immersed in water at 74°C. Swelling efficiency = 1 if the volumetric strain of the epoxy matches the volume of absorbed water. With kind permission from Springer Science + Business Media Adamson (1980) figure 2...

Methylene chloiide formulas are the most common organic chemical removers. The low molar volume of methylene chloride allows it to rapidly penetrate the finish by entering the microvoids of the finish. When the solvent teaches the substrate, the remover releases the adhesive bond between the finish and the substrate and causes the finish to swell. The result is a bhstering effect and an efficient rapid lifting action. Larger molecule solvents generally cannot... 

Generally, conversion from one solvent to another is carried out at low flow rates. The commonly used flow rate for this conversion is 0.2 ml/min for standard columns and 0.1 ml/min for solvent-efficient columns. This minimizes any swelling/shrinking stress put on the column. The temperature of a solvent conversion is chosen to minimize any pressure stress on the column bank. As a general rule, the pressure per column should never exceed 3.5 MPa (500 psi) during solvent conversion. For example, the conversion of a column bank from toluene to trichlorobenzene (TCB) or o-dichlorobenzene (ODCB) is commonly carried out at 90°C. This minimizes the stress on the column due to the higher viscosity of the target solvents. 

Solvent can affect separation in two different ways. Because water is a better solvent for these four columns than water/methanol, based on the swelling or void volume of the columns in Table 17.9, the separation should be better in water than in water/methanol. The relative viscosity of a 0.5% PEO standard from Aldrich (Lot No. 0021kz, MW 100,000) in water and in water/methanol with 0.1 M lithium nitrate is 1.645 and 1.713, respectively. This indicates that the hydrodynamic volume of PEO in water is smaller than in water/methanol. The difference in hydrodynamic volume between two PEO standards should also be larger in water/methanol than in water. Hence, the separation for PEO should be better in water/methanol than in water. The results in Table 17.8 indicate that separation efficiency is better in water than in water/methanol... 

A large amount of water is added to the dehydrated material in order to cause it to swell the swollen structure is preserved when the material is frozen and subsequently dried in vacuo (in the frozen state) to a low moisture content. Some leaching occurs during the treatment with water and this, undoubtedly, further contributes to the increase in the porosity of the solid. Drying of the lyophilized substance can.be completed in a relatively short time in a vacuum oven at an elevated temperature, or at room temperature in the presence of an efficient water adsorbent. 

A recent series of papers [18, 24, 32-34] substantially clears up the three-dimensional polymerization mechanism in the AAm-MBAA system. Direct observation of the various types of acrylamide group consumption using NMR technique, analysis of conversion at the gel-point, and correlation of the elastic modulus with swelling indicate a considerable deviation of the system from the ideal model and a low efficiency of MBAA as a crosslinker. Most of these experimental data, however, refer to the range of heterogeneous hydrogels where swelling is not more than 80 ml ml-1 [24]. 

Unfortunately, reliable data on the equilibrium swelling and long-term stability of hydrogels obtained by this method are not available. It should be noted that crosslinking of polymers with metal ions is one of the few reactions which can be carried out directly in the soil medium, which is efficiently used, e.g., in oil recovery [65, 66]. 

Finally, one more phenomenon is connected with the dependence of swelling on pressure. It is quite clear that the soil layer exerts certain pressure on the SAH particles and this pressure depends on the depth. This factor additively reduces SAH efficiency as a water absorbent. We possess some data, yet unpublished, which directly indicate some decrease of the SAH swelling in soils with the depth of their residence. 

The salt attack is also an important factor determining the SAH efficiency in the soil medium. In terms of Eq. (4.3), it is manifested by a sharp decrease of the coefficients y and B. The hydrogel structure prediction for specific application conditions requires to take into account universal (ionic strength) and specific (collapse) suppression phenomena and, therefore, a rather delicate balancing in search for a compromise between swelling gains due to the network density (n ) and the ionicity ((3). 

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