30 Hindered phenolic antioxidants.Today we take it for granted that polymers can withstand high-speed processing at elevated temperatures and shear rates, and also can take exposure to heat on the job for extended periods without discoloring or embrittlement Embrittlement A general set of phenomena whereby materials suffer a marked decrease in their ability to deform (loss of ductility) or in their ability to absorb energy during fracture (loss of toughness), with little change in other mechanical properties, such . It was not always so. In the 1950s, the best antioxidant available was BHT BHT butylated hydroxytoluene, an antioxidant used in foods, cosmetics, pharmaceuticals, and petroleum products. BHT n. A crystalline phenolic antioxidant used to preserve fats and oils, especially in foods. , a low-molecular weight phenolic phe·no·lic adj. Of, relating to, containing, or derived from phenol. n. Any of various synthetic thermosetting resins, obtained by the reaction of phenols with simple aldehydes and used as adhesives. type that was fugitive and unable to provide long-term protection. Work on more permanent and effective high-molecular-weight hindered phenolics originated around 1955 at Geigy Chemical's Industrial Chemicals Div. (today's Ciba Specialty Chemicals “Ciba” redirects here. For the pre-1971 company, see Novartis. Ciba Specialty Chemicals is a chemical company based in and near Basel, Switzerland. It was formed as the non-pharmaceuticals elements of Novartis were spun out in 1997, following the merger in the ). In early 1963, Geigy launched its new Irganox family, including grades 1076 and 1093, which were initially targeted for PP but with the expectation that they would find use in ABS, HIPS, PVC PVC: see polyvinyl chloride. PVC in full polyvinyl chloride Synthetic resin, an organic polymer made by treating vinyl chloride monomers with a peroxide. , acetal acetal /ac·e·tal/ (as´e-t'l) 1. any of a class of organic compounds formed by combination of an aldehyde molecule and two alcohol molecules. 2. , polyesters, and nylons. Not long after came Irganox 1010, considered the "Cadillac" of antioxidants at the time. It was instrumental in making PP a huge commercial success by extending product lifetimes in higher-heat applications such as food packaging and automotive components. From the 1970s on, many improved hindered phenolic antioxidants arrived from companies like CibaGeigy, American Cyanamid (now Cytec), Great Lakes Chemical (now Chemtura), Uniroyal (now Chemtura), Ashland Chemical, and Mayzo. They soon proved valuable in other polymers such as PE and rubber-modified polymers like HIPS, ABS, and TPEs. Phenolic antioxidants are also widely used in engineering polymers such as PET, polycarbonate, and nylons. These resins have high processing temperatures and are generally designed to be exposed to heat. |
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