Green synthesis of chitin/lignin based-polyurethane composites

Polyurethanes (PU) are still among the most promising high-performance materials in industrial applications. Nevertheless, the development of sustainable and efficient materials is an ongoing challenge for the plastics industry. In recent years there has been growing interest in utilizing natural materials such as chitin and lignin as additives in polyurethane foam production. This study focuses on the utilization of sustainable chitin–lignin filler for polyurethanes with the aim of producing sustainable, cost-effective, and efficient foam materials. A chitin–lignin filler was prepared using a mechanochemical approach, and flexible polyurethane foams (FPUFs) were synthesized with varying amounts of chitin–lignin additive. The resulting foams were characterized using various analytical techniques, including scanning electron microscopy, compression testing, tensile strength analysis, and measurements of surface free energy and contact angle. Possible interactions between the filler and PU were analyzed by means of FTIR spectroscopy. The results show that the addition of chitin–lignin filler improved the mechanical properties (in comparison to pristine chitin and lignin as filler), with a significant reduction in the compression set of the polyurethane foams, a crucial property in the production of seat foams. Synergy was observed between chitin–lignin filler in PU foam. Overall, the study demonstrates the potential of chitin–lignin as a sustainable and efficient natural filler that can be effectively applied on the industrial scale. The combination of these two biopolymers led to a polyurethane composite with better mechanical properties. Additionally, the use of biopolymers (chitin and lignin) as a filler for FPUFs is one of the options for the management of waste materials, which is in line with the idea of sustainable production.