Preparation of biodegradable succinic anhydride esterified lignin-based polyvinyl alcohol film with improved mechanical and thermal properties

In this study, a biodegradable SA esterified lignin-based PVA (SELP) film was created from the purified lignin, polyvinyl alcohol (PVA) and succinic anhydride (SA) under the catalysis of N,N-dimethylbenzylamine through three-step process. The chemical and crystalline characterization of SELP film was implemented to analyze the esterification of SA on the lignin macromolecule and PVA backbone. The research results confirmed the double esterification of lignin and PVA with SA. It was found that the introduction of lignin not only effectively regulated the surface morphologies of SELP films, but also greatly elevated their mechanical strength and thermal stability. Compared with SEP film, the elongation at break and toughness of SEL₅₀P film were raised by 803.4 % and 2130.8 % to 1216.05 ± 5.97 % and 23.2 ± 2.04 MJ/m³, respectively. The largest increase in the tensile strength (5829.4 ± 5.34 kPa) was acquired for the SEL₂₀P film having 20 % lignin dosage. Although in high humidity conditions, SEL₅₀P film also displayed prominent tensile strength (8.12 ± 0.92 MPa) and satisfactory toughness (21.53 ± 2.01 MJ/m³). Meanwhile, even after soaking in water for 24 h, SEL₅₀P film still showed excellent tensile resilience performance. More importantly, SEL₅₀P film has good biodegradability, which can be completely degraded into CO₂ and H₂O by natural microorganisms within 3 months.