Impedance factor

Cheaper raw materials are another way to reduce production costs. This includes, e.g., the minimization of the melamine content in a MUF-resin. An impeding factor can be the (often temporary) shortage of raw materials for the adhesives, as it was the case with sudden price increases for methanol (from which formaldehyde is obtained industrially) and melamine within the last decade. 

The impedance factor is strictly empirical, accounting primarily for the geometry of the soil pore network bnt also for ion exclusion by negative adsorption from narrow pores, and for the increased viscosity of water near charged surfaces. It is similar for all simple ions and molecules. It can be measured by following the self diffusion of a nonadsorbed ion, such as Cl , for which C = 0lCl and hence D =... 

Figure 2.3 Relation between diffusion impedance factor, /l, and moisture content, 6>l, in a range of soils. Numbers shown are % clay contents. Mean of six soils volcanic ash soil. (After Tinker and Nye, 2000 Olesen et al., 2001). Reproduced by permission of Oxford University Press...

Figure 2.4 Relation between diffusion impedance factor, /l, and bulk density, p, in four water-saturated rice soils. Dotted line is the theoretical relation between /l and p for a mixture of different-sized spherical particles (Kirk et al., 2003). Iloilo Epiaquult clay 21% org C 1.04% pH 3.93. Maahas Haplaquoll clay 54% org C 1.83% pH 5.89. Nueva Ecija Epiaquert clay 35 % org C 1.57 % pH 5.25. Tarlac Tropaquept clay 33 % org C 1.06% pH 6.02. Reproduced by permission of Blackwell Publishing...

It is assumed that the impedance factor, /l, is the same for all mobile acids and bases. It is also assumed that the solid equilibrates rapidly with the adjacent solution in cases where it does not, terms for the rates of reaction can be added to the equation. 

Olesen T, Moldrup P, Yamaguchi T, Rolston DE. 2001. Constant slope impedance factor model for predicting the solute diffusion coefficient in unsaturated soil. Soil Science 166 89-96. 

Staunton S. 1990. A comparison of the surface impedance factors of Ca, Na, Rb and Cs derived from their self-diffusion coefficients in various soils. Journal of Soil Science 41 643-653. 

Despite these impeding factors, business companies interested in Chemical Leasing are asked to recognise potential usage, work out its specific advantages, and develop a viable business model with partners. 

Using another electrical analog approach, Klute (26,27) arrived at a similar expression in which the impedance factor was termed the "transmission function." In both cases, however, the properties of the conducting phase are considered not to be influenced by the crystalline phase. Although this was found to be true for sorption, Michaels et al asserted that the crystallites would reduce the mobility of the chains in the amorphous phase and, thus, further reduce penetrant diffusion rates. The "chain... 

The presence of the crystalline phase restricts also the motion of polymer segments causing the diffusion to decrease. The effects of crystalline phase are usually characterized by geometric impedance factor and chain immobilization factor. The diffusion through polymer films is affected by the glassy or rubbery state of the polymer matrix and by stretching of polymer specimen . 

---