Biodegradation of Lignocellulose-Polyester Composite Films in Freshwater and Seawater Conditions

Developing biodegradable material alternatives is crucial to address the fossil-based plastic pollution in marine ecosystems. Natural biodegradable polymers like cellulose exhibit potential plastic alternatives. However, their susceptibility to water and moisture poses challenges when blending with hydrophobic polymers. Thus, chemical modification is often required to enhance cellulose dispersion in hydrophobic polymer matrices, which may hinder its inherent biodegradability. In this study, the aquatic biodegradation and degradation mechanisms of lignocellulose-polyester composite films under aerobic conditions were for the first time explored in simulated freshwater and real seawater environments. The composite films were produced by blending cellulose nanofibrils (CNFs) with polycaprolactone (PCL), a hydrophobic polyester, using lignin nanoparticles (LNPs) as an interfacial compatibilizer. The structural and morphological changes of the composite films were studied using Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). Despite the use of LNPs (poorly degradable in aquatic conditions) and the composite films’ hydrophobicity, the presence of up to 25 wt% PCL and 5wt% LNPs did not prevent the composites from achieving > 85% biodegradation within 42 days, in both fresh water and seawater conditions. The incorporation of CNFs increased the water uptake capability of PCL which helped to increase the films’ porosity, in turn enhancing the film degradation process. This study confirmed that hydrophobizing nanocellulose with biodegradable polyesters and LNPs can preserve the nanocellulose’s inherent coveted biodegradability. Hence, this sustainable approach to developing bio-based composites supports responsible material development, disposal, and end-of-life management. Graphical abstract: (Figure presented.)