Stability antioxidant adsorption

Antioxidants often contain functional groups that are capable of interaction with the filler surface. This can result in antioxidant adsorption depending upon the surface chemistry of the filler and the type of antioxidant. Once adsorbed, the antioxidant becomes ineffective because it is unable to diffuse to, and react with, the radicals that cause polymer degradation. The amount of deactivated antioxidant can he significant, and the usual response in industry is to add more antioxidant to attain the required level of stability. However, that approach raises the cost of the compound significantly. Another commercial approach is to use an epoxy additive that preferentially adsorbs onto the filler surface, physically blocking antioxidant adsorption. That helps to reduce cost, but the epoxy additive is itself still a relatively expensive chemical. 

Abstract. Adsorption of antioxidants (vitamins C and E) from aqueous and ethanol solutions on unmodified and partially hydrophobized nanosilica A-200 was studied using UV spectroscopy and quantum chemical methods with consideration for the solvent effects. Antioxidant power of silica nanocomposites with immobilized vitamins was evaluated by measuring the total polyphenolic index following the Folin-Ciocalteu method. It has been shown that immobilization of vitamins on silica surface leads to their stabilization. Being released from the carrier molecules of vitamins do not lose their antioxidant properties... 

Highly disperse silica is widely used in pharmaceutical formulations as a filler, adsorbent, thickener etc.5 Their high hydrophilicity and the absence of emulsifying ability restrict their application. In contrast to hydroxylated silica, partially or fully hydrophobized silica may exhibit improved properties as a drug carrier. The main goal of this work is to study hydrophobized silica nanocomposites with immobilized vitamins C and E. Investigations of adsorption-desorption processes which involve silica nanoparticles and the antioxidants are described. Factors affecting the antioxidant stability have also been carefully considered. 

Oil (Aa 4-38) determines oil content in a dried sample of oil-bearing material by extraction with petroleum ether. This method is specific for cottonseed, which first must be fumed with hydrochloric acid to prevent oil adsorption to the fiber. Additional methods exist for other oilseeds. Oxygen Stability Index (OSI) (Cd 12b-92) measures the oxidation induction period of fat sample (essentially the time for a sample to exhaust its antioxidant properties) under conditions of the test. 

This volume is including information about thermal and thermooxidative degradation of polyolefine nanocomposites, modeling of catalytic complexes in the oxidation reactions, modeling the kinetics of moisture adsorption by natural and synthetic polymers, new trends, achievements and developments on the effects of beam radiation, structural behaviour of composite materials, comparative evaluation of antioxidants properties, synthesis, properties and application of polymeric composites and nanocomposites, photodegradation and light stabilization of polymers, wear resistant composite polymeric materials, some macrokinetic phenomena, transport phenomena in polymer matrix, liquid crystals, flammability of polymeric materials and new flame retardants. 

However, the opposite effect of the carbon black with highest volatile content on thermal stability was observed. This phenomenon is attributed to the adsorption of antioxidant by the carbon black surface or to the sensitization of thermal oxidative reactions by the surface oxygenated groups present. It has been proved that different behaviour is related to the volatile content, due to the presence of carboxylic and sulphonic acid groups. Not only are the temperature and rate of decomposition influenced by embedded carbon black particles, but also the decomposition products. The presence of 1-alkene oligomers with 3n C atoms is reduced, while 2-alkenes and 1-alkenes with 3n+l C atoms are increased. Carbon black promotes chain scission and participates in the radical transfer reactions. Incorporated particles of carbon black, especially those with small particle size, improve UV durability. ... 

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