Mitigation of ozone-induced adhesion loss in tire cords: influence of temperature and light

Environmental factors such as ozone, temperature, humidity, and UV light can influence the adhesion performance of RFL-coated polyester (PET) tire cords to rubber. Here, the combined effects of ozone, UV irradiation, temperature, and rubber compound chemistry were investigated using H pull-out testing supported by ATR-FTIR, SEM/EDX, and wettability analyses. Mild heat–humidity conditioning (30 min) caused only limited adhesion loss; the maximum reduction was from an indexed value of 100 to 94.6 at 40 °C/80% RH. UV irradiation alone (254 nm) did not measurably reduce adhesion. In contrast, ozone + UV exposure caused pronounced degradation: the indexed H pull-out force decreased from 100 to 46 after 10 min and to 35 after 30 min (ozone concentrations ∼0.4 ppm and ∼1.2 ppm, respectively). Temperature strongly governed ozone sensitivity: under 0.2 ppm O3 (5 min), adhesion deterioration was most severe within a 150–200 °C window, followed by partial recovery above 200 °C up to 240 °C. Rubber compound formulation significantly affected retention under combined aging: relative to the HRH-free compound (22% adhesion drop), adding methylene donors improved performance, with HMT retaining 95%, and HMMM increasing the indexed force to 112% under ozone (∼1.2 ppm) + UV exposure. Surface analyses confirmed oxidation and heterogeneity in the RFL layer after ozone + UV: EDX showed oxygen increased from 20.02 at.% to 25.74 at.%; water contact angle decreased from 91.4° to 84.1°, while surface energy increased from 23.7 to 26.8 mN/m. Overall, the study identifies a critical thermal window for ozone-driven adhesion loss and demonstrates that formulation (notably HMMM) and UV-free environments can mitigate degradation.