Resistivity of extract

Sulfonate Esters. These are marketed as efficient and easily processible plasticizers with good resistance to extraction. They are typically aryl esters of a to alkanesulfonic acid. 

Medical and health-care related appHcations consume about 21,000 t of polycarbonate aimuaHy. Polycarbonate is popular because of its clarity, impact strength, and low level of extractable impurities. Special grades have been developed to maintain clarity and resistance to yeHowing upon gamma radiation sterilization (qv) processes. Leisure and safety appHcations are many and varied, accounting for about 22,000 t of consumption aimuaHy. The... 

Just under the bark of a tree is a thin layer of cells, not visible to the naked eye, called the cambium. Here, cells divide and eventually differentiate to form bark tissue outside of the cambium and wood or xylem tissue iaside of the cambium. This newly formed wood on the iaside contains many living cells and conducts sap upward ia the tree, and hence, is called sapwood. Eventually, the inner sapwood cells become iaactive and are transformed iato heartwood. This transformation is often accompanied by the formation of extractives that darken the wood, make it less porous, and sometimes provide more resistance to decay. 

Extractives and Ash. The amount of extractives in wood varies from 5 to 20% by weight and includes a wide variety of organic chemicals (11). Many of these function as intermediates in tree metaboUsm as energy reserves or participate in the tree s defense mechanism against microbiological attack. The extractives contribute to wood properties such as color, odor, and decay resistance. 

Antioxidants resistant to extraction by lubricants and gasoline are preferred for the stabili2ation of elastomers used in automotive appfications such as gaskets and tubing. Aromatic amine antioxidants, such as A/-phenyl-Ar-(p-toluenesulfonyl)-A-phenylenediamine [100-93-6] (37), with low solubifity in hydrocarbons, are extracted slowly from elastomers and are used for these appfications. 

However, binding the antioxidant chemically to the elastomer chain by copolymeri2ation or grafting is a better solution to this problem. The addition of /V-(4-ani1ino-pheny1)methacrylamide [22325-96-8] (38) to a polymeri2ation recipe for NBR mbber produces a polymer with a built-in antioxidant resistant to extraction (23). 

Mechanism The mechanism of leaching may involve simple physical solution or dissolution made possible by chemical reaction. The rate of transport of solvent into the mass to be leached, or of soluble fraction into the solvent, or of extract solution out of the insoluble material, or some combination of these rates may be significant. A membranous resistance may be involved. A chemical-reaction rate may also affec t the rate of leaching. 

Low molecular weight liquid polyester resins are useful as plasticisers, particularly for PVC, where they are less volatile and have greater resistance to extraction by water than monomeric plasticisers. Examples of such plasticisers are polyfpropylene adipate) and poly(propylene sebacate). In some cases monobasic acids such as lauric acid are used to control the molecular weight. 

Tannins are polyhydroxyphenols. They are soluble in water, aleohols and aeetone and ean eoagulate proteins. They are yielded by extraetion from wood substanee, bark, leaves and fruits. Other components of the extraction solutions are sugars, pectins and other polymeric carbohydrates, amino acids and other substances. The content of non-tannins can reduce wood failure and water resistance of glued bonds. The polymeric carbohydrates especially increase the viscosity of the extracts. 

PVC plastisol coatings are tough, with an abrasion resistance similar to rubber. They are resistant to acids and alkalis but usually are not suitable for solvents because of extraction of the plasticizers in the coating. 

Noller, H. F., Hoffarth, V, and Zimniak, L., 1992. Unusual resistance of peptidyl transferase to protein extraction procedures. Science 256 1416-1419. 

Alkali ions in solution increase the pH, with two consequences. The rate of silica extraction increases with the rise in pH value above 9 and the rate of alkali exchange is reduced. However, since the higher alkalinity favours solution (of silica) further alkali is released by the lattice. The quantity of alkali extracted can be used as a measure of the resistance of glass to attack... 

The insect s choice of food may be governed to a considerable extent, as ours is, by attractants and repellents. In many instances, the actual insecticidal action of plant extractives may be due primarily to an artificially high level of application, while, in fact, the parent plants are only repellent in the field. This repellency may appear to be resistance on the part of the plant, and the chemistry of such resistance factors has begun to receive much-needed attention. For example, Smissman and his coworkers have examined the chemical basis for the inherited resistance of some strains of corn to attack by the European corn borer. 6-Methoxybenzoxazolinone (X) was isolated (2, SO) and shown to be one of the principal resistance factors, and a number of synthetic analogs were found to... 

Borgatti M., Romanelli A., Saviano M., Pedone C., Lampronti 1., Breda L., Nastruzzi C., Bianchi N., Mischiati C., Gambari R. Resistance of decoy PNA-DNA chimeras to enzymatic degradation in cellular extracts and serum. Oncol. Res. 2003 13 279-287. 

In more recent developments siloxane additives (Figure 3.22) exhibit good resistance to extraction, as shown in Figure 3.1 for Soxhlet extraction of HDPE plaques. While nonpolymeric antioxidants (Anox 20 and Anox PP18) were completely extracted after lOh, at the same time more than 40% of the initial concentration... 

UV3346) offer superior compatibility, low volatility, excellent resistance to extraction and contribute to heat stability. The nonextractable nature of these additives makes their quantification challenging. The quantification of Chimassorb 944 in polyolefins is possible using an UV absorption method after dissolution of the polymer [596]. 

Albemarle) has shown unique resistance to extraction from polyolefins. No radioactivity was detected in water run through a MDPE pipe stabilised with 14C-labelled Ethanox 330 for 10 months at ambient conditions, or in an accelerated 3-month test at 80 °C (limit of detection 25ppb). 

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