Lifetime Prediction of Talc-Reinforced Virgin/Recycled Hybrid Polypropylene Composites Using the Arrhenius Model

The thermal durability of virgin/recycled polypropylene (PP) hybrid composites containing post-consumer recycled PP (PC-rPP) and end-of-life vehicle recycled PP (ELV-rPP) at various blending ratios was evaluated, with emphasis on the effect of a long-term thermal stabilizer (LTTS). The formulations were designed with a fixed talc content of 20 wt%, and the recycled series contained 50 wt% recycled feedstock. Accelerated thermal aging was conducted at 135, 145, and 155 °C to determine the time required to reach a 50% retention of the initial tensile strength. A common-slope Arrhenius model yielded an apparent activation energy (Ea,int) of 139.86 kJ/mol (95% Confidence Interval: 123.74-155.98 kJ/mol). Using the model-derived time to 50% retention (tR50) at 135 °C as a reference, direct extrapolation to 100 °C yielded tR50,100 values ranging from 5.11 to 14.04 years. At equivalent blending ratios, the rPP composites incorporating LTTS exhibited significantly extended lifetimes compared to their unstabilized counterparts. Specifically, the tR50,100 values for rPP composites with high ELV-rPP content (above 20 wt%) were comparable to that of the virgin PP (vPP) composite. To supplement the evaluation with absolute strength criteria, an 18 MPa tensile strength threshold was introduced. The resulting t18,100 values spanned 2.59-9.14 years, with all recycled formulations remaining below the performance of vPP under this criterion. These values serve as conditional comparative indices because an activation energy transfer to the 18 MPa endpoint is assumed, and direct validation at 100 °C is absent. The validity of the common-slope approximation is further limited by temperature-dependent residuals and an upper-tail departure in the normal Quantile-Quantile plot.