Heat stabilizers organic phosphites

Market Volume. The total market for PVC heat stabilizers may be about 100 million pounds in the United States and 1 biUion pounds worldwide, half for organotin and half for metal soap-epoxidized fatty ester-organic phosphite systems. 

Organic compound heat stabilizers include not only primary stabilizers that can be used alone (mainly organic nitrogen compounds), but also polyalcohols and phosphite esters with a high boiling point. Phosphite esters are often used together with metal stabilizers to enhance the weather resistance and transparency of composite materials and improve surface color and luster of products. 

Two chemical classes serve as hidroperoxide decomposers antioxidants activated organic compounds of sulfur (long-term heat stabilizers) and organic compounds of trivalent phosphorus (processing stabilizers). Aliphatic phosphites are more effective processing stabilizers than aromatic phosphites and faster consumed. During their action trivalent phosphorus compounds are transformed in pentavalent compounds. 

As mentioned above, many stabilizers are deactivated to other products during their first service for example, phenolic antioxidants to quinonemethides, cyclohexadienones or benzoquinones phosphates are formed from phosphites various oxidation products of sulphides, including organic acids of sulfur, from sul-phidic heat stabilizers and substituted piridin-4-one and open-chain nitroso and nitro compounds, salts and other transformation products arising from HAS. Stabilizers are also lost by diffusion and migration. 

A common aim of directed evolution is to increase the stability of an enzyme to conditions of practical use that may be very different from those the enzyme naturally functions in. Factors such as heat, altered pH, and the presence of oxidants or organic solvents can lead to denaturation or loss of enzyme function. Many researchers have successfully increased the stability of an enzyme to thermal denaturation (41, 42). Work with p-nitrobenzyl esterase uicreased the melting temperature 14°C after six rounds of EP-PCR and recombination without forfeiting enzyme activity (41). As another example, phosphite dehydrogenase catalyzes the formation of phosphate from phosphite, by reducing NAD+ to NADH. However, the usefulness... 

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