Crosslinking coefficient

Fig. 7. Theoretical curves relating soluble fraction S, and crosslinking coefficient, 6, for an initially uniform, random or pseudo-random distribution [2].

Crosslinking of the degraded polymer of degree of polymerization u and u2 is then considered to occur. A new crosslinking coefficient 5, is defined as... 

Our interest from the outset has been in the possibility of crosslinking which accompanies inclusion of multifunctional monomers in a polymerizing system. Note that this does not occur when the groups enclosed in boxes in Table 5.6 react however, any reaction beyond this for the terminal A groups will result in a cascade of branches being formed. Therefore a critical (subscript c) value for the branching coefficient occurs at... 

Of all the techniques, it is those of Group 1 that are likely to give the most realistic data, simply because they measure transport of charged species only. They are not the easiest experimental techniques to perform on polymeric systems and this probably explains why so few studies have been undertaken. The experimental difficulties associated with the Tubandt-Hittorf method are in maintaining nonadherent thin-film compartments. One way is to use crosslinked films [79], while an alternative has been to use a redesigned Hittorf cell [80]. Although very succesful experimentally, the latter has analytical problems. Likewise, emf measurements can be performed with relative ease [81, 82] it is the necessary determination of activity coefficients that is difficult. 

Fig. I. Steady structure of crosslinked MA-EDMA copolymers obtained in solutions of acetic add of different concentrations. K — relative swelling coefficient, Ks — swelling coefficient (by a = 0 and a = 0.5, respectively)...

Fig. 3. Change in relative swelling coefficient Kw during ionization of macroreticular MA-EDMA copolymers obtained in 30% Ac A solution (1-4) and heteroreticular MA-EDMA copolymers obtained in 5% Ac A solution (5,6) with different amounts of the crosslinking agent — EDMA (mol%) /) 1.0 2) 1.5 3) 2.5 4) and 5) 4.0 6) 10.0...

Fig. 4. Swelling coefficients of crosslinked MA-DMEG copolymers as a function of the content of the crosslinking agent 1) pH 2.8 2) pH 12.5...

Fig. 29. Effect of the extent of crosslinking of sulfonated cation exchangers (quantity of cross-linking agent) on diffusion coefficient of tetracycline in sorbent grains 1) SDMDMA, 2) SHMDMA, i) SEDMA, 4) Dowex-50W...

The application of the above methods of calculation has shown that the quasi-diffusion of organic counterions is profundly affected by both the amount of the crosslinking agent in a crosslinked polyelectrolyte and the method of formation of the crosslinked structure [109-112]. Fig. 28 shows the dependence of diffusion coefficients for streptomycin ions on the amount of the crosslinking... 

Thermal expansion — as elasticity — depends directly upon the strength of the intermolecular forces in the material. Strongly bonded materials usually expand little when heated, whereas the expansion of weak materials may be a hundred times as large. This general trend is confirmed by Table 5.1. The coefficient of thermal expansion a was found to be lower in the crosslinked polymers and higher in the less crosslinked or thermoplastic materials as observed by Nielsen [1], In addition, Table 5.1 presents the Young s moduli E of the polymers at ambient temperatures as well as the products a2E. The values of oc2E are all close to 13.1 Pa K 2 with a coefficient of variation of 1.6%. 

The free volume model seems to be more adequate to describe the plasticization behaviour of the systems of lower amine content. According to Eq. (5), the higher is the change of the expansion coefficient the lower is the influence of the diluent volume fraction. The three TGDDM-DDS mixtures cured with 20, 30 and 50 PHR of hardener were characterized l2) by changes of the expansion coefficient at the glass transition, respectively, of 0.63, 1.08 and 2.94x 10 3 °C l. The more dense and stiffer resin crosslinked with 50 PHR of DDS should be, in principle, the less... 

Tubular reactors are used for some polycondensations. Para-blocked phenols can be reacted with formalin to form linear oligomers. When the same reactor is used with ordinary phenol, plugging will occur if the tube diameter is above a critical size, even though the reaction stoichiometry is outside the region that causes gelation in a batch reactor. Polymer chains at the wall continue to receive formaldehyde by diffusion from the center of the tube and can crosslink. Local stoichiometry is not preserved when the reactants have different diffusion coefficients. See Section 2.8. 

Static leak-off experiments with borate-crosslinked and zirconate-cross-Unked hydroxypropylguar fluids showed practically the same leak-off coefficients [1883]. An investigation of the stress-sensitive properties showed that zirconate filter-cakes have viscoelastic properties, but borate filter-cakes are merely elastic. Noncrosslinked fluids show no filter-cake-type behavior for a large range of core permeabilities, but rather a viscous flow dependent on porous medium characteristics. 

Birefringence. The birefringence of a crosslinked Gaussian rubber subjected to an affine deformation is described by the theories of Kuhn and Grun (1 ) and Treloar (2). These predict a stress-optical coefficient given by... 

Kofinas et al. (1996) have prepared PEO hydrogels by a similar technique. In this work, they studied the diffusional behavior of two macromolecules, cytochrome C and hemoglobin, in these gels. They noted an interesting, yet previously unreported dependence between the crosslink density and protein diffusion coefficient and the initial molecular weight of the linear PEGs. 

Hargreaves has suggested that the insolubilization of some closely related polymers is due to photolytic homolysis of the endoperoxide 0-0 bond and subsequent generation of carbon-centered radicals from the O radicals (19). There are several facts that make this an extremely unlikely explanation for the data described here these include the quantitative insufficiency of the maximum amount of endoperoxide reaction obtainable with a few hundred mJ/cm2 dose (homolysis quantum yield <0.5 (46), and extinction coefficient 1 (M cm)-1 (47)), and the synthetic utility of such homolysis reactions in related molecules in the presence of good hydrogen atom donors (implying facile epoxide formation) (48). Clearly the crosslinking observed under N2 is not accounted for by this mechanism. 

As soon as the protein is activated with the heterobifunctional crosslinker, the extinction coefficient determined for pure Amb a 1 no longer applies because the heterobifunctional crosslinker absorbs at 280 nm. At this step in the production of AIC, the manufacturing overhead cost requires the use of a fast protein assay, whereas the exact stoichiometry of the subsequent reaction dictates the use of an accurate and precise method. Hence we developed a new extinction coefficient for the activated protein based on experimental data and demonstrated that within the normal activation range of 9 to 12 crosslinkers per Amb a 1, the new extinction coefficient remained constant. The concentration of the purified activated Amb a 1 determined by this direct absorbance A280 method is more precise and accurate than could be assigned by a colorimetric assay. Consequently, the activated Amb a 1 concentration allows for the accurate addition of 1018 ISS required to consistently produce AIC with optimal activity. 

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