Synergistic dicumyl peroxide-furfural extract oil stabilization of waste polyethylene in asphalt binders: phase stability and short-term oxidative aging

Storage instability and oxidative aging limit the durable use of waste polyethylene (PE) in asphalt binders. This study evaluates a stabilization strategy combining dicumyl peroxide (DCP) crosslinking and furfural extract oil (FEO) compatibilization. Five formulations containing 7 wt% PE, with DCP contents of 0.05–0.30 wt% and FEO contents of 1.0–3.5 wt%, were screened using softening-point difference (ΔSP), separation index (SI), temperature-dependent rheological segregation rate (Rs), and fluorescence microscopy. The selected formulation (HCL; 0.30 wt% DCP and 1.0 wt% FEO) achieved ΔSP of 2.0°C and maintained Rs ≤ 0.20 from 37 to 55°C, yielding an 18°C stability-window breadth on the tested temperature grid. HCL was subsequently evaluated using an L9(34) processing array and rolling thin-film oven test (RTFOT) aging. Across nine stabilized variants, mean penetration retention was 72.28%, the mean softening-point increase was 4.78°C, and the mean empirical fracture-energy index was 1.571 J m−2. FTIR indicated attenuated carbonyl and sulfoxide development, while GPC revealed differences in molecular-weight evolution relative to the non-stabilized control. These findings suggest that DCP/FEO stabilization can improve storage stability and resistance to short-term oxidative aging under the tested conditions. Long-term durability, transferability, and scale-up require further validation.