April 14 news, recently, at the Hannover Tire Technology Expo, ACE Laboratories Company of the United States revealed its latest research results. Studies have shown that tire antidegradants based on 6PPD migrate out of silica-reinforced rubber significantly faster than carbon black reinforced rubber.
Erick Sharp, CEO of Ace Laboratories in Ravenna, Ohio, elaborated on this phenomenon in a keynote speech. He proposed that 6PPD can precipitate from wear particles in silica treaded tires at twice the average migration speed of TWP for carbon black treads. 6PPD, a chemical specifically used to protect tires from ozone and oxygen, has attracted environmental attention in recent years due to the impact of its transformation product 6PPD quinone (6PPDQ) on aquatic organisms, especially salmon.
According to the Carbon Black Industry Network, Sharp's research stems from an abnormal increase in salmon mortality in streams over the past decade, a phenomenon that coincides with the increased use of silica as a rubber filler, which is widely used to improve rolling resistance, traction and tear strength of tires. Sharp emphasized that this was the original intention of their decision to delve into the effects of chemicals associated with silica technology.
Commenting on these new findings, Sharp mentioned that several theories may explain why 6PPD mobility is higher in silica treads. One view is that due to significant differences in morphology between silica and carbon black TWP, these structural differences may increase the interaction between the TWP surface and water. Another view is that silica may provide a more convenient channel for water to enter and exit TWP, thereby accelerating the precipitation of 6PPD.
In addition, Sharp also mentioned that carbon black has a certain "carbon trapping effect" on polar materials, which may be one of the reasons for the low mobility of 6PPD in carbon black. He concluded that these factors combined may explain the higher antioxidant/antiozonant mobility in silica tread compounds.
The study also observed that the increase in mobility was not limited to 6PPD, and that other tire additives, such as zinc and sulfur, also showed similar migration patterns. Currently, Ace Laboratory is further studying the ozone oxidation of TWP in order to obtain more data on the formation of 6PPD-Q. At the same time, they are also exploring the impact of different carbon black to silica ratios in order to establish a correlation between the behaviors of the two fillers.
Sharp concluded that the research team is currently conducting an in-depth exploration to evaluate the effectiveness of various fillers and additives in blocking the "moisture highway" of silica. This research will not only help improve tire performance, but will also have a positive impact on environmental protection.
