Reduction or Replacement of 6PPD through Improved Ozonation-related Crack Resistance with MOLECULAR REBAR

The primary purpose of an antiozonant and antioxidant like 6PPD is to mitigate the cleavage of polymer chains in a tire. However, over time the 6PPD depletes resulting in polymer chain degradation, subsequently followed by the development of surface level microcracks. These microcracks coalesce with use and time forming larger cracks that often result in premature failure of the tire, well before its tread life is finished. MOLECULAR REBAR® (MR) carbon nanotubes have been proven to impart significant abrasion, tear, and crack propagation resistance properties to elastomers. These unique properties are due to the dispersion of individual nanotubes of MR, which when coupled with chemical functionality, results in a well-bound, high aspect ratio, high surface area filler. With the use of MR nanotubes, ozonation-related microcrack propagation will be lessened, preventing coalescence of microcracks, and thus reducing larger crack occurrence. With this additional reinforcement in a tire compound, the quantity of 6PPD used can be reduced, or 6PPD can be replaced with a less effective, but environmentally safer antiozonant- like 77PPD. Treating the effects of polymer ozonation, rather than the preventing the initial ozone degradation, is a unique approach that can be implemented commercially more quickly than the evaluation of a new small-molecule antiozonant- which may require exhaustive environmental testing, in addition to the rubber compound tests. Molecular Rebar Design, LLC will determine what type of carbon nanotube surface functionality is most effective at preventing crack propagation, and then formulate tire sidewall elastomer compounds with those nanotubes while varying the type and quantity of antiozonant present in the sidewall compounds. These rubber compounds will undergo ozone aging to simulate real-world conditions, whereafter the aged samples will be tested for differences in crack resistance, lifetime, tear strength, and intrinsic strength. These experiments will culminate in a sidewall compound formulation that is less environmentally damaging than incumbent compounds that utilize a full loading of 6PPD. The resultant experimental compound will be designed to have the same, or better, expected lifetime as an incumbent sidewall compound.