Chemical Degradation of Waste Polyethylene Terephthalate and Its Application in Developing Asphalt Additives

To address the low resource-recovery efficiency of waste polyethylene terephthalate (PET) and the shortage of high-performance eco-friendly asphalt modifiers, PET-derived functional additives were fabricated in this work via zinc-acetate-catalyzed alcoholysis of waste PET followed by repolymerization of the obtained degradation fragments. Owing to the diverse origins of waste PET feedstock, noticeable fluctuations in molecular-weight parameters are commonly encountered. Nevertheless, waste PET can be effectively depolymerized into relatively low-molecular-weight derivatives under the proposed catalytic alcoholysis conditions. This study systematically investigated the effects of different PET degradation pathways on the molecular architecture, molecular-weight distribution, and thermal stability of as-prepared PET-derived asphalt additives. It further uncovers the intrinsic structure–performance relationships between molecular characteristics and critical asphalt properties, including rheological behavior, interfacial adhesion, high-temperature rutting resistance, and low-temperature elastic recovery. Homogeneous alcoholysis conducted at 220 °C enables efficient depolymerization of waste PET to yield derivatives with tailorable molecular weights. The resultant amphiphilic alcoholysis products can reduce asphalt viscosity and ameliorate water stability, rendering them promising warm-mix anti-stripping additives. By contrast, repolymerized PET derivatives are capable of constructing cross-linked networks within asphalt matrix, which substantially boost the high-temperature modulus and fatigue resistance of modified asphalt. Distinct from conventional physical blending approaches that are plagued by inferior interfacial compatibility and marginal performance improvement, this chemical modification strategy affords PET-based additives with tunable functions for different engineering scenarios. These findings provide technical support for high-value recycling of waste PET and the development of sustainable low-carbon asphalt materials.