Conditionally Degradable Polyester-Based Containers A Comprehensive Mechanistic Framework for Long-Term Use Stability and Environmentally Triggered Degradation Without Persistent Micro- and Nanoplastic Formation

The accumulation of plastic packaging waste and the pervasive presence of micro- and nanoplastics in natural environments have become defining environmental challenges of the twenty-first century. Beverage containers based on polyethylene terephthalate (PET) exemplify this dilemma: they provide excellent mechanical performance, chemical inertness, and food safety during use, yet persist for decades after disposal, undergoing fragmentation rather than true degradation. Fragmentation-driven weathering processes produce micro- and nanoplastic particles that remain chemically intact and biologically inaccessible, thereby extending the environmental lifetime of polymer-derived matter. In response, a wide range of biodegradable, compostable, and oxo-degradable plastics has been proposed. However, many of these systems suffer from premature degradation during use, dependence on narrowly defined industrial composting conditions, or degradation pathways dominated by oxidative embrittlement and uncontrolled fragmentation. These mechanisms often accelerate microplastic generation rather than eliminating it. The central limitation of such approaches lies not in insufficient degradation speed, but in the incorrect sequencing of degradation mechanisms, where mechanical disintegration precedes chemical depolymerization. This preprint presents a comprehensive mechanistic and materials-design framework for conditionally degradable, bio-derived polyester containers engineered to remain chemically and mechanically stable during industrial processing, commercial distribution, and extended domestic reuse, while undergoing chemically mediated degradation only after disposal under specific environmental conditions. The framework explicitly defines compositional criteria for degradable containers that minimize the likelihood of persistent micro- and nanoplastic formation by prioritizing controlled chain scission and subsequent bioassimilation over oxidative fragmentation. By integrating polymer architecture, additive logic, degradation kinetics, and environmental trigger synergy, this work provides a theoretical foundation for the development and evaluation of next-generation packaging materials with environmentally meaningful end-of-life behavior.