Hutchinson: 6ppd more than a pressing issue

EDINBURGH, U.K.—The need to replace 6ppd, an antioxidant and antiozonant essential for tire performance, is more than just a pressing matter for the tire industry—as highlighted at RubberCon 2023 in Edinburgh.

At the conference, Marie Yrieix of Hutchinson S.A. reported on the French industrial rubber product maker's search for alternative ways of providing similar levels of protection against thermo-oxidation, ozonation and fatigue degradation.

While 6ppd is a highly effective antiozonant for rubber used in many industrial applications, it has been found to generate a "highly toxic quinone," Yrieix said at the conference, held May 9-11.

There are many parameters to consider when seeking to substitute 6ppd, not least type of degradation—oxidation, ozone, fatigue or a combination of these, she said.

A fundamental target here, she said, is to match the effectiveness of 6ppd in trapping hydrocarbon and peroxide radicals due to its high reactivity with ozone at rubber surfaces.

Other important factors include end-use conditions, the elastomer matrix and the potential for interactions between any replacement chemical with other compound components.

Yrieix noted that alternatives, such as IPPD (isopropyl-phenyl-1,4-phenylene diamine), DTPD, (bis(methylphenyl)-1,4-benzene diamine) and DPPD (diphenyl-p-phenylene diamine), present toxicity issues.

The search for alternatives to 6ppd, therefore, needs to be broadened out to include other diphenyl amine-based—as well as phenol-, quinoleine- and olefin-based—chemicals.

According to Yrieix, test findings have shown that "protection against fatigue degradation" represented the main challenge for the substitution of 6ppd.

The way forward, she suggested, could well require "combining different non-toxic anti-degradants" to fully protect rubber products from oxidation, ozone and fatigue degradation.