Eco-friendly non-isocyanate polyurethane and carboxymethyl cellulose composite films reinforced with sodium lignosulfonate for sustainable packaging applications

Plastic pollution is a major environmental crisis. Biodegradable polymers are a viable solution to plastic waste due to their sustainable character and reduced environmental footprint. However, despite these environmental benefits, many industries are yet to adopt biodegradable polymers largely due to their high moisture sensitivity and limited mechanical performance. This study aims to develop multifunctional and high-performance green packaging materials by reinforcing sodium lignosulfonate (LS) into non-isocyanate hydroxyurethane (NIHU)/carboxymethyl cellulose (CMC) composites. Understanding the mechanism of interaction between CMC, NIHU and LS provides insights into the underlying chemistry and offers an opportunity to tailor the properties and functions of CMC-based hybrids. Structural analyses confirmed that the polyphenolic moieties of LS interacted effectively with the CMC/NIHU matrix through hydrogen bonding interactions. We showed that addition of LS changed morphology and surface chemistry without disrupting the cellulosic backbone. The synergistic interaction between the LS skeleton and the CMC/NIHU network enabled the development of exceptionally stiff hybrids with a tensile strength of up to 8.5 MPa tensile strength, a water vapor transmission rate of ~40%, DPPH radical scavenging activity of 85%, and nearly complete UV blocking. The insights gained from this study provided a better understanding on the molecular-level interactions between CMC, NIHU and LS and highlighted the potential for commercial exploration of LS-containing cellulosic materials for food packaging applications.