Effect of Vegetable-Derived Linoleic Acid in Passenger Car Radial (PCR) Tyre Tread, Sidewall and Ply Compound

Stearic acid, octadecanoic acid, is a primary ingredient used in the rubber industry as an activator for vulcanization. Linoleic acid, derived from vegetables, contains a similar number of carbon atoms and has a similar concentration of acid functional groups (193 mg KOH/g) with a higher unsaturation content, as indicated by its iodine number (134 g/100g) compared to stearic acid (2 g/100g). Gas chromatography mass spectrometry (GC-MS) analysis reveals the location of unsaturation at the 9th and 12th positions. When mixed with tread, sidewall, and ply compounds, linoleic acid exhibits lower activation energy (Ea) and a higher vulcanization reaction rate constant, and a higher order of the reaction compared to the control compounds. These unique properties of linoleic acid result in enhanced modulus at 300% strain with improved tensile strength. Dynamic mechanical analysis shows that the experimental tread compound achieves a higher modulus than the control compound. The fatigue properties of the experimental sidewall demonstrate a slightly longer lifespan (273 kc) compared to the control compound (268 kc), while both exhibit similar ozone protection. For the ply compound, the adhesion between the ply compound and the fabric is stronger in the experimental compound (16.25 Kgf) than in the control (15.51 Kgf).