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Inhibited polymer concentration

A series of experiments were carried out at varying polymer concentrations to examine the effect of varying nitrile concentration (the nitrile concentration range was 86-258 mM). The relationship between polymer (nitrile) concentration and reaction rate for this system is shown in Figure 3. It shows that increasing the NBR concentration, (increase in the concentration of nitrile functionality) inhibits the catalytic activity of the catalyst i.e. the observed rate constants showed an inverse dependence on nitrile concentration. [Pg.129]

Polyvinylchloride was the host polymer in a study of the diffusion of dimethyl-phthalate, dibutylphthalate, and dioctylphthalate, performed by Maklakov, Smechko, and Maklakov 60) between room temperature and 110 °C. Azancheev and Maklakov 61) extended this work to include polystyrene as host, and to dependences of diffusion on concentration. They concluded that the macromolecules did constrain and trap the phthalate molecules at high polymer concentration, but without inhibiting the mobility of these diluents at lower polymer concentrations, e.g., in the gel. They used a version of the free volume theory to give a semi-quantitative explanation of the temperature and molecular size dependence of phthalate diffusion. [Pg.21]

Thus preliminary studies show that while there was no overt evidence of activity by the platinum polyamlnes on the cell cultures (CPE) at the eiqiloyed polymer concentrations, there was biological activity In that the polymers were Inhibiting or stimulating viral replication. [Pg.230]

After optimizing the assay conditions, including ionic strength, pH, temperature, activator (Ca ) concentration, and polymer concentration, a calibration curve was developed, which allows the lipid substrate concentration to be determined from the fluorescence intensity. The calibration curve allows the enzyme catalysis kinetics parameters (e.g.. Km and Vmax) to be measured. This PLC turn-off assay is effectively inhibited by known inhibitors (F and EDTA), which demonstrates that the sensor relies on the specific catalysis reaction by PLC. It has been demonstrated to be a sensitive (detection limit 0.5nM enzyme concentration), fast (<5 min), and selective (good specificity over phospholipase A and D, and other nonspecific proteins) PLC assay, which can be carried out at very low initial substrate concentration (in the range of micromolar to nanomolar). [Pg.48]

Fig. 3.19. Structure of inhibited polymer coatings (a) the inhibitor is evenly distributed within the film-forming layer, (b) the inhibitor layer is localized within the coating volume, (c) the inhibitor is concentrated on the substrate surface. (1) metal substrate, (2) polymer coatings, (3) an inhibitor particle... Fig. 3.19. Structure of inhibited polymer coatings (a) the inhibitor is evenly distributed within the film-forming layer, (b) the inhibitor layer is localized within the coating volume, (c) the inhibitor is concentrated on the substrate surface. (1) metal substrate, (2) polymer coatings, (3) an inhibitor particle...
In general, agents capable of inhibiting one RNA virus will inhibit other RNA viruses but each DNA virus must be evaluated separately. The platinum polyamines were studied against RNA viruses. The behavior toward RNA viruses was varied with some showing little activity but the majority showing inhibition of viral replication at polymer concentrations below which tumoral inhibition is found (< 1 (tg/ml). [Pg.220]

In order to inhibit polymer oxidation, the antioxidants have to be present in sufficient concentration at the various oxidation sites. Antioxidants must, therefore, be physically retained in polymers during the high-temperature processing/fabrication operations and under aggressive service conditions their performance can sometimes be dominated by physical phenomena such as compatibility with, or volatility and extract-ibility from, the polymer matrix. [Pg.829]

Distribution and Poiymer Morphoiogy. In order to inhibit polymer oxidation, sufficient concentration of antioxidants must be present at the various oxidation sites. Examination of the distribution of photoantioxidants in typical commercial semicrystalline poljmiers, such as polyolefins, has shown (5,22,115) that they are rejected into the amorphous region on the boundaries of spherulites. Such nommiform distribution of antioxidants leads to an increase in their concentration in the amorphous region, which is most susceptible to oxidation since the crystalline phase is normally impermeable to oxygen (5). However, in the case of polymer blends, a nonuniform distribution of antioxidants can undermine the overall stability of the blend, especially if it does not occur in favor of the more oxidizable component in the formulation. [Pg.7762]

Although solvent-shift method enjoys simplicity and versatility in selection of the polymer, the outcome of this study is somewhat questionable as the organic solvent may interfere with precipitation kinetics and thermodynamics, and may not reflect amorphous solid system. In addition, supersaturation or precipitation inhibition potential of specific polymers is highly concentration dependent. Since local in vivo drug-polymer concentrations are difficult to predict, it is thus challenging to define suitable biorelevant polymer concentrations for in vitro experiments. [Pg.180]

To inhibit polymer formation and oxidative degradation during shipment and subsequent storage, an inhibitor TBC (4-tert-butylcatechol), is added. TBC prevents polymerisation by reacting with oxidation products (peroxides forming free radicals) in the presence of a small amount of oxygen. The inhibitor level must be maintained above a minimum concentration at all times which is 4 to 5 ppm. The standard level of TBC is 10 to 15 ppm. [Pg.73]

However, if the total polymer concentration is increased, the entire nucleation becomes inhibited and a cooperative mechanism results in new complex fiber-related morphologies, which are not predictable from the crystal morphologies triggered by the individual DHBCs and strongly depend on the mixing ratio of the two functional DHBCs [343] (Fig. 26d). [Pg.54]

Tryptic soy agar plates were seeded with suspensions of the test organism to produce an acceptable lawn of test organism after 24 hours of incubation. Shortly (within several minutes) after the plates were seeded, the tested compounds (0.1 mg of solid or designated polymer concentration if in solution) were deposited on the plates. The plates were incubated and inhibition noted. [Pg.151]

The diethyltin and also the dimethyltin products were studied because of their outstanding antibacterial activities. Both showed good inhibition of the Balb/3T3 cells at about a polymer concentration of 10 pg/mL. Again, the polymers showed mild activity against the HTB 75 cancer cell line. Greater than 50% inhibition was found for the diethyltin polymer at 30 pg/mL. [Pg.67]

While the products exhibited some tumor activity against L929 and HeLa cells, the activity was less than that of products derived from diamines. About 50% inhibition of both cell lines occurred at a polymer concentration of 10 pg/mL. [Pg.144]

With increase in polymer concentration, the spherulites becomes larger, indicating inhibited nucieation of GP-1 at a higher polymer concentration. Reprinted with permission from Ref [24]. [Pg.106]

The synthesis described met some difficulties. D-Valyl-L-prolyl resin was found to undergo intramolecular aminoiysis during the coupling step with DCC. 70< o of the dipeptide was cleaved from the polymer, and the diketopiperazine of D-valyl-L-proline was excreted into solution. The reaction was catalyzed by small amounts of acetic acid and inhibited by a higher concentration (protonation of amine). This side-reaction can be suppressed by adding the DCC prior to the carboxyl component. In this way, the carboxyl component is "consumed immediately to form the DCC adduct and cannot catalyze the cyclization. [Pg.237]

Because chloroprene is a flammable, polymerisable Hquid with significant toxicity, it must be handled with care even in the laboratory. In commercial quantities, precaution must be taken against temperature rise from dimerisation and polymerisation and possible accumulation of explosive vapor concentrations. Storage vessels for inhibited monomer require adequate cooling capacity and vessel pressure rehef faciUties, with care that the latter are free of polymer deposits. When transportation of monomer is required, it is loaded cold (< — 10° C) into sealed, insulated vessels with careful monitoring of loading and arrival temperature and duration of transit. [Pg.39]

Bulk polymerisation is heterogeneous since the polymer is insoluble in the monomer. The reaction is autocatalysed by the presence of solid polymer whilst the concentration of initiator has little effect on the molecular weight. This is believed to be due to the overriding effect of monomer transfer reactions on the chain length. As in all vinyl chloride polymerisation oxygen has a profound inhibiting effect. [Pg.315]

KCl-polymer (potassium chloride-polymer) muds can be classified as low solids-polymer muds or as inhibitive muds, due to their application to drilling in water-sensitive, sloughing shales. The use of polymers and the concentration of potassium chloride provide inhibition of shales and clays for maximum hole stability. The inverted flow properties (high yield point, low plastic viscosity) achieved with polymers and prehydrated bentonite provide good hole cleaning with minimum hole erosion. [Pg.674]


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See also in sourсe #XX -- [ Pg.247 ]




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