Race to replace 6PPD

London - This year should see significant progress in the drive to find alternatives to 6PPD (6-paraphenylene-diamine) antioxidants, though advances will be incremental and system-based rather than involving any particular breakthrough chemistry.

That’s according to Erick Sharp, founder and CEO of ACE Laboratories, which is actively involved in efforts to find a safer alternative to 6PPD: focusing mainly on supporting laboratory screenings of potential alternatives and assessing the migration of chemicals from wear particles into water.

Developed to protect against oxygen, ozone and cracking, 6PPD is used widely use in tire and rubber applications. Almost all commercial tires employ the ingredient, especially in the sidewall and tread compounds.

However, leaching of 6PPD from tire wear particles has been found to be harmful to certain species of salmon and trout in the US – via transformation by-product 6PPDquinone (6PPDQ) on reaction with oxygen and ozone in the environment.

The issue has prompted regulators in the US, Europe and elsewhere to push for the phase-out of 6PPD with threats to impose restrictions on use of the long-established component of compounds used in the production of tires and rubber products.

“Through our laboratory screenings we feel there are alternatives that merit full scale evaluation,” said Sharp, while pointing out that “none of these alternatives would be considered direct replacements for 6PPD.

Indeed, few in the industry expect to see a drop-in alternative emerge any time soon, particularly as the new chemistry will have to replicate the performance of 6PPD within rubber= compounds across a wide range of processing and end-use conditions.

As Sharp of Ravenna, Ohio-based ACE Laboratories explains: “Most alternatives to 6PPD interact differently with the typical cure systems used in tire compounds.

This means the substitution also requires adjustments to the incumbent cure package.”

Meanwhile, added the US expert, most alternatives also require, at least, a dual combination of antiozonants to meet the same dynamic ozone and flex fatigue performance that 6PPD provides

“ACE has long predicted that the replacement of 6PPD would be a system replacement and not just a one-for-one material replacement,” Sharp continued in a written statement to ERJ.

There has been encouraging progress in this area, with the development of methodology to analyse chemical migration from wear particles into water.

According to Sharp, this has been “highly beneficial” in understanding how 6PPD and 6PPDq reach peak concentrations in water streams and “allowed for the assessment of other solutions such as torturous path barriers and molecular weight modification.”

Asked about likely areas of progress in 2026, Sharp expects that the industry will see a lot of work on system changes as well as on evaluating full anti-degradant and cure systems.

“There have been recent industry claims of an even closer offset being developed,” he added. “I expect we will see data and evaluations start on that technology as well.

“Now that option “Now that options are advancing, we should see more clarity on timelines and expectations for regulators. Any new findings in human impact studies could greatly impact timelines and requirements.”

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