The increasing diffusion of dispersion‑coated fiber‑based packaging has created a growing need for advanced analytical methodologies capable of assessing coating integrity and degradation during recycling. In this work, we introduce a process‑integrated method designed to detect, isolate, and characterize microplastic (MP) fragments generated from thin polymeric films during hydropulping. The approach combines controlled laboratory repulping, aligned with industrial conditions, with a multi‑stage isolation workflow based on sequential filtration and fine‑mesh screening, taking and adapting standard methodologies recognized and used within the sector.
To enhance traceability, selected coating formulations were tagged with rhodamine‑B, enabling semi‑automated MP detection through complementary imaging techniques including fluorescence microscopy, optical microscopy, and Raman spectroscopy. These instruments supported cross‑validated identification of polymeric particles and allowed characterization of fragmentation behavior down to 20 µm. For a representative 8 g/m² thin‑film coating, over 75,000 secondary MPs were recovered from solid residues, with an average equivalent diameter of 75.4 µm and a particle density of 4.7 particles/mm². The study demonstrates how this integrated platform enables the systematic evaluation of thin‑film fragmentation pathways during repulping.
Because this work represents one of the first attempts to apply such an approach to coated fiber substrates, the tests are best understood as preliminary applications of the methodology, illustrating its diagnostic potential rather than providing exhaustive environmental metrics. The framework is inherently scalable and reproducible, offering a powerful foundation for equipment benchmarking, coating‑failure analysis, and process‑control improvement across recycling and coating‑development environments.
Overall, the methodology establishes a new analytical capability for the coating community, supporting Safe and Sustainable by Design (SSbD) strategies aimed at developing next‑generation, high‑performance, and recyclability‑oriented barrier coatings.