Accelerator adsorption

The retarding effect of sodium sulphate in the application of mol larly-dispersed dyes has already been referred to. It must be emphas that the effect is only apparent when dyeing at low/>H values, and in nei solutions the presence of electrolytes accelerates adsorption. The expl tion which is usually accepted is that when the concentration of anioi the liquor is increased, there is more competition for the positive sit the fibre ... 

This problem is relatively easy to deal with as the curing agents adsorbed may be displaced by addition of a polar additive, such as diethylene or polyethylene glycol, triethanolamine, etc. These materials are preferentially adsorbed on to the filler surfaces and thus inhibit accelerator adsorption [38]. 

Falco AD, Matzocca AJ, Corcuera MA, Eceiza A, Mondragrai I, Rubiolo H, Goyanes S (2009) Accelerator adsorption onto carbon nanotubes surface affects the vulcanization process of styrene-butadiene rubber composites. J Appl Polym Sci 113 2851-2857... 

The developer is generally a solvent in which the components of the mixture are not too soluble and is usually a solvent of low molecular weight. The adsorbent is selected so that the solvent is adsorbed somewhat but not too strongly if the solvent is adsorbed to some extent, it helps to ensure that the components of the mixture to be adsorbed will not be too firmly bound. Usually an adsorbate adheres to any one adsorbent more firmly in a less polar solvent, consequently when, as frequently occurs, a single dense adsorption zone is obtained with light petroleum and develops only slowly when washed with this solvent, the development may be accelerated by passing to a more polar solvent. Numerous adsorbat are broken up by methyl alcohol, ethyl alcohol or acetone. It is not generally necessary to employ the pure alcohol the addition from 0 5 to 2 per cent, to the solvent actually used suffices in most cases. 

Surface heterogeneity is difficult to remove from crystalline inorganic substances, such as metal oxides, without causing large loss of surface areas by sintering. Thus in Fig. 2.14 in which the adsorbent was rutile (TiO ) all three adsorbates show a continuous diminution in the heat of adsorption as the surface coverage increases, but with an accelerated rate of fall as monolayer completion is approached. 

Retarders and Accelerators. Materials that control hardening of cement may be either organic or inorganic. Retarders are often incorporated in oil well cementing and hot-weather concrete appHcations, whereas accelerators may be useful for cold-weather concrete appHcations in which higher rates of reactivity are desirable. In most cases, these admixtures are used in low concentrations, suggesting that they act by adsorption. 

Surface area can accelerate the decomposition of chlorine dioxide up to a point, but sufficient area appears to inhibit catalytic decomposition by adsorption of the intermediates. For example, the presence of fluffed wood pulp or glass wool is reported to stop the explosive decomposition of chlorine dioxide (27). 

Dmg loading can be accompHshed by dispersion or adsorption. In dispersed systems, a dmg is blended into a polymer by mechanical means, such as a kneader. The viscosity of the polymer, and the size and concentration of the dmg, need to be optimized to minimize aggregates. Dmgs can also be absorbed by equiUbrating a polymer in a dmg solution. The absorption rate can be accelerated by introducing an appropriate solvent to swell the polymer. AH solvents would then have to be removed. 

Conversely, the adsorption of anions makes the potential more negative on the metal side of the electrical double layer and this will tend to accelerate the rate of discharge of hydrogen ions. This effect has been observed for the sulphosalicylate ion and the benzoate ion . 

Sakurada et al.88, 145, 146 hydrolyzed aliphatic esters having various hydrophobicities with cation-exchange resins, Dowex 50 w, and found a close correlation between the accelerating factor and the degree of ester adsorption toward the resins. 

Local breakdown of passive film results from a localized increase in the film dissolution rate at the anion adsorption sites that are attacked by chloride ions, as will be discussed later, in the same manner as substrate metal dissolution. Such acceleration of the dissolution rate was ascribed to the formation of metal chlorides24 or the local degeneration of film surface by the formation of surface electron levels.7... 

As shown in Fig. 24, the mechanism of the instability is elucidated as follows At the portion where dissolution is accidentally accelerated and is accompanied by an increase in the concentration of dissolved metal ions, pit formation proceeds. If the specific adsorption is strong, the electric potential at the OHP of the recessed part decreases. Because of the local equilibrium of reaction, the fluctuation of the electrochemical potential must be kept at zero. As a result, the concentration component of the fluctuation must increase to compensate for the decrease in the potential component. This means that local dissolution is promoted more at the recessed portion. Thus these processes form a kind of positive feedback cycle. After several cycles, pits develop on the surface macroscopically through initial fluctuations. 

The reinforcing properties measured as M300/M100 are similar for the two vulcanized samples. However, the cured A1 compounds show lower ultimate elongation at break, higher curing rate (T90), and shorter breakdown time (T2), which are the signs of lower adsorption of accelerators on the A1 particles surface. 

H2 adsorption is weak on the anatase surfaces [8], No dissociative adsorption of H2 takes place over the smooth surfaces of Au at temperatures below 473 K [9,10]. On small Au particles, adsorption is possible at low temperature. Dissociative adsorption of H2 can be accelerated by the negatively charged molecular oxygen species at steps, edges, comers of Au particles [5]. 

Therefore, we arrive at the same conclusion for the mechanism of COad oxidation in the lower potential regime as for Pt-free Ru(OOOl), postulating that at potentials E < 0.55 V, only strongly bound OHad/Oad species are present in the mixed COad + OHad/Oad adlayer, which are not reactive towards CO2 formation, while for E > 0.55 V, additional, weakly adsorbed OHad/Oad species are formed, which can react with the (likewise destabilized) COad- Similar to COad oxidation on a Ru(OOOl) surface, the reaction starts by dissociative adsorption of H2O on the Ru(OOOl) surface (no shift in the onset potential). In this case, however, the Pt islands can accelerate the reaction by accepting the Hupd resulting from a homolytic dissociation process. Thus, we tentatively propose a mechanism for CO oxidation at potentials between the reaction onset up to the bending point (see also Lin et al. [1999]), which is... 

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