Rapid screening 'can help tire makers address 6PPD issues'

Hanover, Germany - Concern over the potential environmental and health impacts of 6PPD (6 p-phenylenediamine) antiozonants in tire & rubber compounds has raised the need for research in this area.

Migratable antiozonants, such as 6PPD, are critical for non-wearable areas of the tire such as sidewall and in the tread lugs, explains Erick Sharp, CEO, Ace Laboratories.

Tread surface applications are not as critical as the rubber will wear down and expose fresh antiozonant, the Ravenna, Ohio-based expert noted in written comments to ERJ.

Based, he said, on standard tire compound formulations and the mass area of a typical passenger tire, roughly 60% of the mass volume of 6PPD in a tire comes from the sidewall.

"The 6PPD in the tread is the quickest to enter the environment due to tire wear particles while the 6PPD in the sidewall migrates out over many years," said Sharp.

Indeed, according to the Ace Laboratories leader, it is estimated that much of the sidewall 6PPD migrates out as 6PPD/q during post life of the tire.

“This creates concerns for landfill run-off and secondary applications that utilise scrap tire," he said. "Our analysis on GTR has shown an average of around 50% of total 6PPD remaining."

Sharp went on to highlight how capabilities to rapidly screen new antiozonant options can help in the development of 6PPD alternatives and mitigations.

“A ‘fail fast’ approach to new solutions will speed up R&D and allow step gains to be made in addition to setting the path towards longer term replacements,” said the CEO. 

An effective approach here is a "correlative lab-scale approach" that factors in maintaining mechanical property performance and weatherability alongside toxicology of ozonated wear particles.

“We have found these screenings can be completed in five to six weeks,” reported Sharp, adding that the method “provides go/no-go directions and helps set trendlines on paths to improvement.”