Adsorption of plasticizer

The morphology of cement hydration products is very little affected by plasticizers [349]. In some works the reduction of ettringite crystal size [367] and of calcium hydroxide [368] in the presence of lignosulphonates is reported. This effect can be attributed to frequently long lasting adsorption of plasticizer particles on the sirrface of crystals [367]. 

In general, the extent of adsorption of plasticizers is inversely proportional to their solubility in water. The organic carbon-water partition coefficient, K., is a compoimd-specific term that allows the user to estimate the mobility of a plasticizer in saturated soil-water systems if the amount of organic carbon in the soil is known. A Kqc value is a measure of the affinity of a chemical to partition to organic matter which in turn will control the mobility of the solute in water. Organic carbon-water partition coefficients were compiled for the 23 plasticizers (Table 18.12). There is considerable range in the measured... 

The most relevant drawback in talc applications is caused by its absorption of polymer process additive. This is a subject of intensive research and patent activity. The treated talc inhibits the adsorption of plastic film additives onto the talc. Surface treating means coating, partial coating, or using an effective amount of modifier to inhibit the adsorption of other additives. A functionalized polydialkyl, preferably polydimethylsiloxane is used for surface treatment. Bis-(12-hydroxystearate) terminated polydimethylsiloxane, is a preferred agent used for the surface treatment of talc (but can also be used in conjunction with other antiblocking agents, such as, diatomaceous earth, calcium carbonate, and synthetic silica). 

Adsorption of t-PA to process equipment surfaces consisting of either stainless steel or glass was minimized by adding the detergent polyoxyethylene sorbitan monooleate (Tween 80) to the semm-free culture conditioned media at 0.01% (vol/vol). The equipment was also rinsed, before use, with phosphate buffered saline (PBS) containing 0.01% Tween 80. Hydrophilic, plastic equipment was used whenever possible. AH buffers were sterile filtered. Sterile filtration of Hquids and gases is usually carried out using 0.2 or 0.45 p.m filters. 

Physical and ionic adsorption may be either monolayer or multilayer (12). Capillary stmctures in which the diameters of the capillaries are small, ie, one to two molecular diameters, exhibit a marked hysteresis effect on desorption. Sorbed surfactant solutes do not necessarily cover ah. of a sohd iaterface and their presence does not preclude adsorption of solvent molecules. The strength of surfactant sorption generally foUows the order cationic > anionic > nonionic. Surfaces to which this rule apphes include metals, glass, plastics, textiles (13), paper, and many minerals. The pH is an important modifying factor in the adsorption of all ionic surfactants but especially for amphoteric surfactants which are least soluble at their isoelectric point. The speed and degree of adsorption are increased by the presence of dissolved inorganic salts in surfactant solutions (14). 

The situation becomes most complicated in multicomponent systems, for example, if we speak about filling of plasticized polymers and solutions. The viscosity of a dispersion medium may vary here due to different reasons, namely a change in the nature of the solvent, concentration of the solution, molecular weight of the polymer. Naturally, here the interaction between the liquid and the filler changes, for one, a distinct adsorption layer, which modifies the surface and hence the activity (net-formation ability) of the filler, arises. Therefore in such multicomponent systems in the general case we can hardly expect universal values of yield stress, depending only on the concentration of the filler. Experimental data also confirm this conclusion [13],... 

Preservative availability may be appreciably reduced by interaction with packaging materials. Examples include the permeation of phenolic preservatives into the rubber wads and teats of multi-dose injection or eye-drop containers and by their interaction with flexible nylon tubes for creams. Quaternary ammonium preservative levels in formulations have been significantly reduced by adsorption onto the surfaces of plastic and glass containers. Volatile preservatives such as chloroform are so readily lost by the routine opening and closing of containers that their usefulness is somewhat restricted to preservation of medicines in sealed, impervious containers during storage, with quite short use lives once opened. 

The sample water container should be made of appropriate materials to avoid adsorption of the chemical of interest on the vessel surfaces. In most cases, a glass bottle may be better than a plastic bottle. The bottle is washed with an organic solvent in advance and also washed with sample water just before sampling. The bottle should be tilled to the limit with water and capped tightly with a Teflon seal to prevent contamination. The top 1-cm of water is not taken to prevent the mixing of floating materials such as oil. 

These techniques are especially useful for studies of the adsorption of reactants, intermediates and products of electrode reactions. The simplest case corresponds to adsorption that is so strong that the electrode can be removed from the solution, rinsed and its activity measured without interference from desorption. When this procedure is impossible, the activity of the adsorbate can be measured by the electrode lowering method . The radioactive counter is placed under the bottom of the cell, which is made of a plastic foil. The electrode can be located at large distances from the bottom or can be placed so close to the bottom that only a thin layer of solution remains beneath it. The radioactivity values at the two electrode positions permit determination of the adsorbate activity. This procedure can be repeated many times, thus supplying data on the kinetics of the adsorption process. 

There are several positive factors using BSA in the basolateral medium. First, it mimics the in vivo situation where the circulating blood provides an excellent base for sink conditions due to a large volume and content of serum proteins such as albumin (serum protein content and alpha-glycoproteins) [108]. Second, serum albumin hinders adsorption onto plastic surfaces and filters and thereby stops the... 

Electron emission occurs when plastic deformation, abrasion, or fatigue cracking disturbs a material surface. Triboelectrons are emitted from freshly formed surface. The emission reaches a maximum immediately after mechanical initiation. When mechanical initiation is stopped, the emission decays with time. Strong emission has been observed for both metals and metal oxides. There is a strong evidence that the existence of oxides is necessary. The exoelectron emission occurs from a clean, stain-free metallic surface upon adsorption of oxygen (Ferrante 1977). 

Stabihzation may also be achieved by altering reaction conditions (e.g., pH, temperature, ionic strength, etc.). In other instances, loss of activity may attend the adsorption of the enzyme to the walls of the reaction container (e.g., glass or plastic can strongly interact with proteins). Using a different container or simply including a spectator protein (e.g., albumin) may increase the degree of stability. 

Any detectable effect on the reaction or behavior of a particular system by the interior wall of the container or reaction vessel. Because proteins can form high-affinity complexes with glass and plastic surfaces, one must exercise caution in the choice of reaction kinetic conditions. Wall effects can be discerned if one determines catalytic activity under different conditions that minimize or maximize contact of the solution with the container. In principle, an enzyme-catalyzed reaction should proceed at the same rate if placed in a capillary or a culture tube however, contact with the wall is maximized in a capillary, and wall effects should be more prominent. Some investigators add bovine serum albumin to prevent adsorption of their enzyme onto the container s walls. 

The pivotal role that superplasticizers play in the formulation of self-leveling mortars is due to the dramatic effects they produce on flow behavior. Such effects are believed to be derived by the adsorption of the admixture on the surfaces of cement grains, thereby providing surfaces of a similar or zero charge which are mutually repulsive. They thus fully disperse cement particles, freeing more water for lubrication and reducing interparticle attraction. Both yield stress and plastic viscosity are decreased and the decrease is greater for yield stress it may be completely eliminated if sufficient admixture is added so that Newtonian behavior is observed (Fig. 7.25) [75, 76]. 

The specific adsorption of H2P04 ions that accompany the UPD of Zn + ions on Pt (platinized electrodes obtained by Pt electrodeposition on the gold-plated plastic foil) electrodes was studied by using a radiotracer method with P phosphate species in the presence of a great excess of C104 ions [196]. It was found that the specific adsorption of species induced... 

Adsorption is also a problem at trace levels. Few solutions below a concentration of 10 pg cm- can be considered to be stable for any length of time. Various preservatives to guard against adsorption of metals on to glassware have been reported in the literature. Common precautionary steps are to keep the acid concentration high and to use plastic laboratory ware. 

Samples should be collected aseptically in nonpyrogenic containers. Reused depyrogenate glassware or sterile, disposable polystyrene plastics are recommended to minimize adsorption of endotoxin. 

The amount of surface adsorption of a number of proteins ranging in molecular mass from 6.5 to 670 kDa and isoelectric point (pi) from 4.3 to 10.5 to several commonly used container surfaces (glass vials either untreated, siliconized, sulfur treated or Purcoat treated plastic vials polyester + 0.3%, polyester 5x0, PP, and nylon). A 5-mL volume of protein solution was added to each vial, yielding a surface-to-volume ratio of 2.4cm2/mL. No correlation was found between the amount adsorbed and the molecular mass or isoelectric point, although glass surfaces appeared to bind more protein under the experimental conditions examined [156]. 

Gloss vessels are not used for very dilute solutions, because ions are adsorbed on the glass. Plastic bottles are better than glass for dilute solutions. Adding strong acid (0.1-1 M) to any solution helps minimize adsorption of cations on the walls of the container, because H competes with other cations for ion-exchange sites. 

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