Location: Bioproducts Research
Title: Efficient computational and experimental probes for kinetic scavenging in rubber antiozonantsAuthor
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Rossomme, Elliot |
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Dong, Chen |
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McMahan, Colleen |
Submitted to: ACS Applied Polymer Materials
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/6/2024 Publication Date: 12/18/2024 Citation: Rossomme, E.C., Dong, C., McMahan, C.M. 2024. Efficient computational and experimental probes for kinetic scavenging in rubber antiozonants. ACS Applied Polymer Materials. Volume 7:1,309-318. https://doi.org/10.1021/acsapm.4c03060. DOI: https://doi.org/10.1021/acsapm.4c03060 Interpretive Summary: Globally, the largest use of natural and synthetic rubber is for tires. All rubber tires are vulnerable to degradation from oxygen, light, heat, and especially ozone. Antiozonant additives are required for tire safety and longevity, but the most-used antiozonant chemical, 6PPD, reacts with ozone to form 6PPDQ. This chemical enters waterstreams and presents a serious aquatic ecological hazard, especially to coho salmon. The USDA Rubber Lab is developing safer, biobased antioxidant alternatives, and advancing the tools and scientific understanding underlying their use. In this study, a laboratory method for screening possible replacements is proposed, and results compared to computated chemical properties, which are shown to predict in-lab performance. Technical Abstract: Since the discovery of 6PPD quinone and its severe toxicity to aquatic organisms, development of safe(r) rubber antiozonants (AO3s) has become imperative. Rubber AO3s must, by definition, protect rubber compounds against degradation due to ozone (O3), a function that is critical to long-term performance of commercial rubber products, most notably in the tire industry. Identification of candidate AO3s is a challenging problem, owing to both the susceptibility of virgin rubber compounds to ozonolysis and the stringent performance requirements for tires. While AO3s are known to protect rubber compounds through combined mechanisms of kinetic scavenging and film formation, aspects of each of these are underexplored. Herein, we develop the use of various experimental and computational metrics—gel permeation chromatography (GPC) and solution viscometry, as well as ground state density functional theory—for the quantitative determination of kinetic scavenging ability across a benchmark data set of 32 rubber antidegradants. We demonstrate an efficient screening protocol for kinetic scavengers, and discuss the implications for design of 6PPD alternatives, particularly those that have been proposed in recent literature. |