Solvent-free cellulose diacetate/polycaprolactone biocomposite films: Tunable soil-burial behavior and antimicrobial activity

The persistence of conventional plastic films has increased demand for functional alternatives with controllable end-of-life behavior and less solvent-intensive manufacturing. In this study, polycaprolactone/cellulose diacetate (PCL/CDA) biocomposite films with and without carvacrol emulsion (CE) were produced by a solvent-free thermo-mechanical route. The effects of CDA and CE on morphology, interfacial interactions, crystallization, barrier and mechanical properties, antimicrobial activity, and 72-day soil-burial mass loss were evaluated. Structural characterization and molecular docking suggested composition-dependent local non-covalent interactions within the matrix, without evidence of new covalent bond formation. P95-CDA5-CE achieved the highest E. coli reduction rate of 90.53%, while P80-CDA20-CE showed a tensile strength of 3.88 N/mm² and light transmittance below 5%. The latter showed a soil-burial mass loss of 8.58% after 72 d, compared with 5.78% for neat PCL. Within the 72-d dataset, first-order kinetic fitting yielded a model-derived Dmax of 8.514% and v0 of 1.100%·d⁻¹ for P80-CDA20-CE. PCA and hierarchical clustering showed close associations among water-related properties and soil-burial behavior. Process-level comparison showed that the solvent-free film-forming route avoided DCM/acetone use for polymer dissolution, reducing fabrication-stage burdens. These findings support the development of cellulose-derived functional films for potential use in short-lifecycle antimicrobial packaging and disposable protective products.