Role of Weathering on the Disintegration of Compatibilized Polymer Blends and Their Release of Microplastics

The increasing environmental presence of microplastics and nanoplastics constitutes a critical concern for environmental integrity and public health, with notable repercussions across aquatic systems, terrestrial ecosystems, and both human and animal health. These particles—defined by their dimensions of less than 5 mm—mainly originate from direct production (primary microplastics) or from the breakdown of larger plastic materials (secondary microplastics) via degradation and fragmentation processes. Polymer blends currently represent an acknowledged contributor to this phenomenon, as they incorporate both a dispersed phase, already in the microplastic size range, and a continuous matrix that, upon degradation, generates further microparticles, thus acting as both primary and secondary sources of microplastics (and nanoplastics). Despite this, the actual behavior of polymer blends—especially those based on polyolefins and polyesters—remains underexplored. In the present study, two types of polyolefin/polyester blends, one with a compatibilizing agent and one without, were subjected to mechanical fragmentation and photo‐oxidative degradation in order to replicate the most common microplastic formation pathways. The results revealed that exposure to photo‐oxidation significantly increases the release of microplastics, whereas compatibilization markedly decreases this release, both in pristine and weathered samples. These results underscore the critical role of morphological characteristics and compatibilization strategies in influencing microplastics generation.