With increasing focus on the environmental impact of traditional tire additives, new materials are being explored to ensure safety and sustainability without compromising performance.
The tire industry is one of the largest consumers of rubber compounds and the raw materials that go into them. Every year, more than 8.5 million tons of carbon black are used in tire manufacturing, alongside thousands of tons of other additives and fillers. Many of these materials pose risks to the environment and living organisms. Among them, the antiozonant 6PPD has raised particular concern.
Replacing 6PPD
6PPD is a chemical compound used to protect rubber from cracking and degradation caused by ozone exposure. However, when exposed to atmospheric ozone, it forms 6PPD-quinone, a toxic substance harmful to both humans and certain aquatic organisms. As global regulatory bodies begin to tighten restrictions and sustainability expectations rise, the tire industry is seeking safer, more effective alternatives.
Collaborative Research at Black Donuts
To address this challenge, Material Development Engineer Justus Rantala conducted his Master’s Thesis at Black Donuts in collaboration with Tampere University, under the supervision of Essi Sarlin (Tampere University) and Jouni Lepistö (Black Donuts). The research explored possible replacements for 6PPD, experimentally evaluating several candidates in rubber tire compounds. Of the materials tested, 77PD emerged as the most promising, delivering an ozone protection comparable to 6PPD when properly formulated.
The compounds were tested for rheological, mechanical, and ozone-resistance properties under both static and dynamic conditions, with comparative analysis against a 6PPD reference compound and a control compound without antiozonants.
Key Findings
The results showed that changing the antidegradant affected nearly all properties of the rubber compound. While several materials required formulation adjustments to achieve comparable performance, a few emerged as particularly promising. The study also assessed non-traditional materials.
Nanographene showed potential as both a reinforcing filler and partial antiozonant, improving mechanical performance while possibly reducing reliance on chemical additives. K Stoff R, a wax-based compound, offered surface-level protection and could complement primary antiozonant more effectively than typically used waxes. Renewable Functional Filler (RFF), tested as both an antiozonant and a substitute for carbon black, maintained the compound’s protective qualities while improving sustainability. Additionally, octyl gallate and Irganox 1520, both known antioxidants, demonstrated limited antiozonant properties.
Among these, 77PD, a phenylene-diamine-based compound, demonstrated the closest overall performance match to 6PPD. It provided comparable ozone resistance and, in some conditions, even outperformed 6PPD.
Advancing Material Research
Although no single compound fully matched the performance of 6PPD, the results suggest that 77PD, at the right concentration, could offer a viable and more environmentally friendly path forward for tire manufacturing. When optimized in dosage and formulation, 77PD may serve as a direct substitute for 6PPD.
This summary is based on research by Justus Rantala, completed as a Master’s Thesis at Tampere University in collaboration with Black Donuts Oy (2025). The experimental work was supported by ACE Laboratories (USA) and Black Donuts’ in-house R&D team, including Jarkko Mällinen and Antti Suonio.
The findings were also featured in the October 2025 issue of Tire Technology International, highlighting the growing importance of sustainable-material innovation within the global tire community.
Black Donuts’ InTire Labs continues this work through advanced research on bio-based and recycled materials with a reduced environmental footprint compared to conventional alternatives, using modern testing equipment and simulation tools to validate performance across full tire applications. The lab’s customized testing capabilities help clients develop next-generation rubber compounds that meet both regulatory and performance requirements. Through collaborations like Rantala’s thesis, InTire Labs reinforces Black Donuts’ long-term commitment to sustainable innovation, regulatory readiness, and measurable performance improvement across the tire value chain.
Reference:
Rantala, J. (2025). Assessment of the current status of the rubber antiozonant 6PPD and exploration of alternative options. Master’s Thesis, Tampere University.
Available at: https://trepo.tuni.fi/handle/10024/227524
