Aging Resistance Improvement of Rubber–Plastic-Based TPE-Modified Asphalt System with Different Plastic Types

This study evaluated the aging resistance of bitumen modified with integrated rubber–plastic thermoplastic elastomers (TPEs). Surface-activated low-Mooney reclaimed rubber was compounded with recycled high-density polyethylene, low-density polyethylene, or polypropylene by twin-screw reactive extrusion using a maleic anhydride-grafted styrenic block copolymer compatibilizer. Reference binders contained styrene–butadiene–styrene (SBS), rubber alone, or individual polyolefins. Aging comprised the rolling thin-film oven test, pressure aging vessel conditioning of oven-aged residues, and ultraviolet exposure. Dynamic shear rheometry, Fourier transform infrared spectroscopy, and atomic force microscopy characterized rheological, chemical, and topographic changes. The largest rutting factor and carbonyl aging indices occurred after sequential oven and pressure aging under the selected conditions. The TPE-modified binders showed lower rutting factor and carbonyl aging indices and smaller relative roughness increases than the SBS reference under each protocol. Among the three TPE formulations, the low-density polyethylene composite had the lowest rutting factor aging indices, whereas the high-density polyethylene composite had the lowest carbonyl aging indices and relative roughness increases after pressure and ultraviolet aging. These findings support the laboratory aging-resistance potential of integrated TPEs, with improved interfacial compatibility providing a plausible explanation. The approach offers a route for the high-value utilization of waste rubber and plastics.