Uniroyal chemicals bob mazaika4/9/2023 ![]() Radical naps for peroxy (COO *) andĪlkoxy (CO *) radicals are the familiar amines and phenols. Most conventional antioxidants either trap the oxy radicals orĭecompose the hydroperoxides (COOH). The structure of the polymer determines how much energy can beĪlso, carbon radicals (C *) are highly energetic, and few materialsĬan effectively trap out these intermediates. If the polymer absorbs too much energy, the bond will break. Initiation really depends on the strength of the carbon-carbonīond. In the oxidation process, as indicated in figure 2. Tensile X elongation product, is often used as the most sensitiveĪntioxidants are materials that can interfere with any of the steps Following the change in tensile strength, or the ![]() Natural rubber and butyl rubber are two polymers thatĭegrade by reversion. Unimolecular cleavage to lower molecular weight fragments, which isĬalled reversion. During aging, tertiary alkoxy orĬarbon radicals are generated which undergo beta scission, or Scission is favored in polymers that areīranched or have many side groups. Limitations in this publication, only elongation change is presented,īut the complete suite of properties measured can be obtained byĬontacting the authors to request the references listed.Ī few polymers tend to undergo reversion or chain scission in the Typically, for these rubber polymers, including EPDM, the change inĮlongation is a most sensitive indicator of aging. TheĬreation of new crosslinks leads to hardening and embrittlement. Two free radicals canĬombine to terminate each other, which results in a new crosslink. Generated, suggested by the heavier arrows. Hydrogen from the polymer backbone to form yet more carbon radicals.Įach time through the cycle, additional free radicals are Will decompose under heat to form two more free radicals: an alkoxy Generate another carbon radical and a hydroperoxide. Peroxy radicals can abstract a hydrogen from the polymer backbone to In the presence of oxygen, peroxy radicals are formed. Shown in figure 1, the carbon radicals enter into a cyclic oxidation Polymer bonds to form carbon radicals to start the aging process. Any form of energy-heat, light or mechanical stress can break The aging of polymers (and people) occurs through a free radical SaidĪnother way, compared to changes observed at a service temperature ofġ50C for EPDM, it would take about 8,000 times as long to see a Reaction rate occurs between room temperature and 70C. Oxygen reacts with the polymer the rate approximately doubles for eachġ0C increase in temperature. Heat can greatly increase the rate at which Oxygen combined with the polymer can seriously degrade the physical Rubber articles are susceptible to aging. APA style: Compounding EPDM for heat resistance.Compounding EPDM for heat resistance." Retrieved from MLA style: "Compounding EPDM for heat resistance." The Free Library.
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |