Influence of bleached and unbleached bagasse cellulose on the rheology of PVA-based bio-composites

The increasing demand for environmentally friendly food packaging materials has driven the development of bio-based polymers reinforced with natural fibers. Poly (vinyl alcohol) (PVA) is widely studied for its film-forming ability, transparency, biodegradability, and suitability for food-contact applications. Cellulose derived from agricultural by-products, such as sugarcane bagasse, represents an abundant and renewable reinforcement that can enhance the structural and functional properties of polymer-based systems. Few studies have systematically investigated PVA composites reinforced with cellulose extracted from sugarcane bagasse via alkaline treatment, and even fewer have compared bleached and unbleached fibers obtained through a controlled extraction process. Since fiber surface chemistry can influence dispersion, polymer-fiber interactions, and processing behavior, such comparisons remain important. Therefore, this study aims to systematically investigate the influence of bleached and unbleached bagasse-derived cellulose on the rheological behavior of PVA-based suspensions. Cellulose was extracted using alkaline treatment, with or without hydrogen peroxide bleaching, and incorporated into PVA solutions at concentrations of 2 wt% and 4 wt%. Steady shear and oscillatory rheological measurements were performed (plate-plate geometry, 1 mm gap, 25 °C). The incorporation of cellulose induced a transition from near-Newtonian to shear-thinning behavior and increased the elastic contribution, particularly at higher fiber loading. Bleached cellulose tended to promote a more homogeneous dispersion and slightly more stable viscoelastic behavior, although further structural characterization would be required to confirm this observation. These rheological changes are relevant for processing operations such as film casting and coating. Overall, this study provides insight into the role of bagasse-derived cellulose in modifying the rheological behavior of PVA systems and highlights its potential for the development of bio-based materials for packaging applications.