Efficient Computational and Experimental Probes for Kinetic Scavenging in Rubber Antiozonants

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.