Multivariate Evaluation of Nanocopper–Perlite Reinforced Carboxymethyl Cellulose Films for Sustainable Food Packaging

The growing environmental burden associated with petroleum-based plastics has intensified research into biodegradable alternatives for food packaging. Carboxymethyl cellulose (CMC) is a promising biopolymer due to its renewability, transparency, and film-forming ability; however, its high hydrophilicity and poor moisture barrier performance limit broader application. In this study, the individual and combined effects of nanocopper (0.05 wt%) and perlite (1 wt%) on the physicochemical, surface, optical, and water vapor barrier properties of glycerol-plasticized CMC films were systematically investigated. Composite films were prepared by solution casting and characterized using atomic force microscopy (AFM), contact angle measurements, water vapor permeability (WVP), solubility, moisture content, color analysis, and scanning electron microscopy (SEM). Univariate statistical analyses were complemented by multivariate techniques, including principal component analysis (PCA), hierarchical cluster analysis (HCA), MANOVA, PERMANOVA, and partial least squares regression (PLSR), to elucidate structure–property relationships. The incorporation of nanocopper increased surface hydrophobicity and altered optical properties, while perlite reduced moisture content and modified surface morphology, consistent with its porous mineral structure. The combined nanocopper–perlite system exhibited lower water solubility, improved structural homogeneity, and distinct multivariate property profiles relative to single-filler and control films. Film thickness emerged as the dominant predictor of WVP in the regression and PLSR models applied in this study, whereas AFM-derived roughness parameters showed limited direct influence on moisture transport. Multivariate analyses consistently indicated formulation-driven clustering, identifying perlite as the primary contributor to global property shifts, with nanocopper exerting secondary, property-specific effects. Overall, these results demonstrate that low-loading hybrid mineral–metal fillers can be used to tailor the performance of CMC-based films, providing a promising strategy for the rational design of biodegradable packaging materials with tunable moisture resistance and functional properties.