Chemical stabilization antioxidants

Antioxidants. The 1,2-dihydroquinolines have been used in a variety of ways as antioxidants (qv). For example, l,2-dihydro-2,2,4-trimethylquinoline along with its 6-decyl [81045-48-9] and 6-ethoxy [91-53-2] derivatives have been used as antio2onants (qv) and stabilizers (68). A polymer [26780-96-1] of l,2-dihydro-2,2,4-trimethylquinoline is used in resins, copolymers, lubricant oils, and synthetic fibers (69). These same compounds react with aldehydes and the products are useful as food antioxidants (70). A cross-linked polyethylene prepared with peroxides and other monomers in the presence of l,2-dihydro-6-ethoxyquinoline produces polymers with a chemically bonded antioxidant (71). 

When two antioxidants are used together, a synergistic improvement in activity usually results. Synergism can arise from three combinations (1) homosynergism — two chemically similar antioxidants (for instance, two hindered phenols) (2) autosynergism — two different antioxidants functions that are present in the same molecule (3) heterosynergism — the cooperative effect between mechanistically different classes of antioxidants, such as the combined effect of primary and secondary antioxidants. Thus, combinations of phenols and phosphites are widely used to stabilize synthetic rubbers. 

These considerations lead to the assumption that the practical aspects of the problem lie in the possibility of obtaining PCS-based thermally resistant materials, catalysts for some chemical reactions, antioxidants, stabilizers, photochromic substances, and materials combining valuable mechanical properties with special electrical (particularly semiconductive) properties. 

Chemical and thermal stabilizers both inactivate the byproducts of degradation processes, preventing them from causing further damage to the polymer. Their chemical structure and mobility in the part define their effectiveness in any given polymeric system. The most common type of chemical stabilizers are antioxidants. 

In certain brilliantine compositions, vegetable and animal oils are used as substitutes for mineral oil. In these systems, because of their potential for rancidity, antioxidants must be included. Other alternatives to mineral oils that have found utility in brilliantines are the polyethylene glycols which come in a variety of solubilities and spreading properties. Use of these materials offers the advantage of chemical stability to rancidity. Other additives found in brilliantines to improve their aesthetics include colorants, fragrance, medicated additives, lanolin, and fatty acid esters. 

Once good physical stability of an emulsion is insured, its commercialization mandates chemical stability of the incorporated drug and other essential components for at least 18 months. Key factors that affect the chemical stability of pharmaceutical emulsions include drug stability in oil, drug stability in aqueous media, drug concentration in oil and emulsion, phase volume ratio, droplet size, presence of excipients, and presence of air and/or peroxide radicals. As mentioned earlier, choice of appropriate antioxidant is important. 

The stabilizers chosen for evaluation include different types of heat and light stabilizers selected to represent different mechanisms of action as well as chemical compositions (ArJi). Types of stabilizers evaluated include benzotriazole and benzophenone light stabilizers [ultraviolet (UV) light absorbers], hindered amine light stabilizers (HALS, catalytic radical scavengers), hindered phenol heat stabilizers (antioxidant radical scavengers), and thioester heat stabilizers (antioxidant hydroperoxide decomposers). 

Other Uses for Aniline. Aniline currently is used as a raw material in most of the major groups of rubber-processing chemicals accelerators, antioxidants and stabilizers, and anti-ozonants. The most important of these are the thiazole derivatives and substituted para-phenylenediamines. The demand for aniline in these rubber-processing uses is expected to grow at less than 1 percent/year. In agricultural chemicals, the major use for aniline is as a raw material in the manufacture of amide herbicides for controlling annual... 

In this fraction, not only the fatty acid composition is important. Another important feature is the natural presence of a high amount of vitamin E (a-tocopherol), 0.59-2.6 mg/100 g in the seeds (Coulter and Lorenz, 1990 Ryan et al., 2007 USDA, 2005), which acts as a natural defense against lipid oxidation (Ng et al., 2007). This fact could lead to a very stable oil from QS, with vitamin E acting as a natural antioxidant. The (p + y)-tocopherol content in quinoa whole flour has been reported as 3.1-5.5 mg/100 g (Ruales and Nair, 1993 Ryan et al., 2007). The chemical stability of the lipids in quinoa flour was studied by Ng et al. (2007), who... 

Properties Clear liquid. D 1.218 (21C), mp 16.8C, bplllC(15 mm Hg). Soluble in water and alcohol. Use Stabilizer, antioxidant, catalyst, chemical intermediate. 

Use Chemical intermediate, antioxidant, ingredient in stabilizer systems for resins. 

Products Derived by Alkylation. An examination of the products obtained as a result of alkylation shows that this unit process is used in the making of anesthetics, antipyretics, alkaloids, antiseptics, detergents, dyes, explosives, flavors, h3T)notics, intermediates, lubricants, medicinals, perfumes, photographic chemicals, plasticizers, plastics, resins, S3mthetic rubber, rubber chemicals (accelerators, antioxidants, modifiers, stabilizers), solvents, soporifics, synthetic gasoline, etc. 

Rubber chemicals, primarily antioxidants (qv), stabilizers, and antiozonants (qv), account for 12% of the demand for aniline worldwide. Important agricultural uses for aniline derivatives include fungicides, insecticides, animal repellents, and defoHants. It is estimated that less than 5% of the aniline produced in 1988 was consumed for agricultural chemicals. 

The combination of poly(arylene ether) (PAE) resins with PAs into com-patibilized blends results in improved overall properties, such as chemical resistance and high strength. The properties of these blends can be further enhanced by the addition of various additives, such as impact modifiers, flame retardants, light stabilizers, processing stabilizers, heat stabilizers, antioxidants and fillers. 

Many papers describe the use of natural or modified CDs to encapsulate polyphenolic compounds. A review of the literature concerning the inclusion of polyphenolics in CDs was very recently published. In the numerous papers available on the subject, molecular inclusion has been shown to improve the chemical stability, the antioxidant activity, the solubility, and/or the bioavailability of various natural polyphenolics (Figure 36.14). 

Synonyms Phenyididecyl phosphite Empirical C26H47O3P Formula C6H50P(OCioH2i)2 Properties Nearly water-wh. liq. alcoholic odor m.w. 438.64 dens. 0.940 (25/15.5 C) m.p. 0 C flash pt. (COC) 218 C ref. index 1.4785 Precaution Combustible Uses Heat stabilizer, antioxidant for resin systems, esp. PVC chemical intermediate lubricant, processing aid for PVC Manuf./Distrib. Akcros Am. http //www.akcros.com, GE Spec. http //www.ge.com/specialtychemicals Trade Name Synonyms Mark DDMPP t[Crompton/Witco Vinyl Addit.] Stavinor DDPP [Ceca SA http //www.ceca.fr]... 

Toxicology TSCA listed Precaution Combustible Uses Stabilizer in polymers, chemical intermediate antioxidant and EP agent in lubricants... 

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