Hutchinson researching 6PPD replacement options

Edinburgh, UK – The need to replace 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene diamine) is not just a pressing matter for the tire industry – as highlighted at RubberCon 2023 in Edinburgh.

At the conference, Marie Yrieix of Hutchinson SA reported on the French industrial rubber products 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 anti-ozonant for rubber used in many industrial applications, it has been found to generate a “highly toxic quinone”, Yrieix explained at the conference held 9-11 May.

There are many parameters to consider when seeking to substitute 6PPD, not least type of degradation – oxidation, ozone, fatigue, or a combination of these – the Hutchinson presenter set out.

A fundamental target here, she explained, is to match the effectiveness of 6PPD in trapping hydrocarbon & 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.

We will report further on the RubberCon 2023 conference in the July/August issue of European Rubber Journal magazine.