Comparative Screening of Ethyl Cellulose Grade, Casting Solvent, Plasticizer, and Nanofiller Effects on Solvent-Cast Film Properties

Conventional flexible food packaging often relies on multilayer structures based on non-biodegradable petrochemical materials to achieve the required barrier performance, generating persistent waste and making recycling difficult. Replacing these systems with simpler cellulose-derived alternatives remains challenging, particularly because moisture protection is difficult to achieve with inherently hygroscopic materials. Ethyl cellulose (EC) is a rare cellulose derivative that is hydrophobic, thermoplastic and, being an ether rather than an ester, hydrolytically stable. Yet much of the foundational knowledge of EC film formation comes from pharmaceutical coating, where permeability is deliberately engineered rather than suppressed, and where each study varies one parameter in its own matrix. However, their relative effects have rarely been compared using the same film-preparation and testing conditions. We prepared different EC film formulations at a fixed EC concentration of 5 wt.% and systematically varied commercial grade, solvent system, plasticizer, or nanofiller while maintaining consistent casting and testing conditions. Solvent system and plasticizer formulation produced significant differences in water vapor transmission rate (WVTR), whereas commercial EC grade and nanofiller type and loading did not significantly affect WVTR. Plasticizer formulation produced the widest variation in mechanical properties, with tensile strength ranging from 4 to 49 MPa, compared with 12–34 MPa across the solvent systems. Apparent MnSEC showed no consistent relationship with film performance; notably, the highest-MnSEC grade exhibited the lowest tensile strength among the seven commercial grades. Tributyl citrate and glycerol at 0.1 wt.% jointly gave the best strength–elongation balance; ZnO- and SiO2-filled films showed the highest mean mechanical values but none differed significantly from the unfilled control.