Development of wood derived bioplastics and its physico-mechanical characterization

Abstract

The global market for bioplastics is rapidly expanding, driven by the increasing demand for biodegradable polymers, especially in emerging economies. Despite only comprising 1% of the annual plastic production, bioplastics offer significant environmental benefits by reducing CO2 emissions and enabling new end-of-life management options such as composting. The development of wood-based bioplastics (lignocellulosic bioplastics) represents a sustainable alternative to traditional petrochemical plastics, addressing both environmental and waste management challenges. Utilizing lignocellulose biomass not only transforms waste into valuable materials but also supports a circular economy, fostering sustainable development and environmental stewardship. These materials, abundant and non-edible, are a major source of renewable organic matter from agricultural and industrial activities. In this background the study ‘Development of wood derived bioplastics and its physico mechanical characterization’ was formulated with objectives as to develop wood derived bioplastics and evaluate its physical and mechanical characteristics. The study comprises in two sections, development of lignocellulosic bioplastics (LCBP) and its characterization. For the production of LCBP various raw materials like mixed sawdust and Melia dubia sawdust have been used and evaluated. Among these, sawdust from Melia wood was found as a suitable raw material for producing lignocellulosic bioplastic. Starch films were produced using corn starch and glycerol as plasticizer, to compare its properties with wood derived bioplastics. The sawdust was treated with deep eutectic solvent (DES), which was prepared using choline chloride and oxalic acid to deconstruct the structure of wood and to obtain the lignocellulose slurry. When water is added to the slurry, lignin gets re-attached with the cellulose fibres, producing a dense and compact arrangement. It is later ultrasonicated using a probe ultrasonicator at 800W for 30 minutes. The slurry is then mixed with recycled cellulose fibres (RCF) obtained from recycled paper in various concentrations and hot pressing is done for 15 minutes to yield the final LCBP. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) images of LCBP showed a continuous lignocellulose matrix with dispersed cellulose fibers. Processed into micro/nanofibrils, the cellulose was encased by lignin, acting as a natural binder. The tensile strength test revealed that incorporating RCF enhanced the mechanical strength of the bioplastics. Samples with the highest RCF content exhibited the greatest tensile strength, attributed to optimal reinforcement, while those with the lowest RCF content demonstrated the weakest strength due to inadequate cellulose reinforcement. The Fourier Transform Infrared Spectroscopy (FTIR) spectrum showed similar peaks in sawdust, and lignocellulose slurry, showing the preservation of lignin even after treatment. X-ray diffraction (XRD) patterns indicated the cellulose I crystalline structure was preserved post-treatment, with the bioplastic showing a 42.43% crystallinity index which is 19.43% higher than raw wood powder. The thermal gravimetric analysis (TGA) curve showed increased thermal stability for LCBP when compared with starch film. As lignocellulose content increased, the bioplastic's water contact angle increased upto 105.30 for pure lignocellulose, indicating strong hydrophobicity. Higher lignin content also reduced water absorption due to lignin's hydrophobic nature. The biodegradability of the LCBP was studied using soil burial test and was compared with starch film and compostable plastic (ISO 17088) and found that starch film achieved 88% biodegradation in one week and was fully degraded in 14 days. LCBP showed 50% degradation in one week and 55.97% in two weeks, outperforming compostable bioplastic (1.59% degradation in two weeks). From the study it was found that the LCBP has very good physical and mechanical properties which is comparable with commercially available alternatives and shows very good degradability, thereby addressing other environmental concerns too.