Efficient Computational and Experimental Probes for Kinetic Scavenging in Rubber Antiozonants

Abstract

Since the discovery of 6PPD quinone and its severe toxicity to aquatic organisms, the development of safer 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 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 35 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.