SYNTHESIS AND CHARACTERIZATION OF POLYURETHANE DERIVED FROM RENEWABLE SOURCES

Abstract

The increasing environmental concerns and health hazards associated with conventional polyurethanes (PUs) have driven the exploration of sustainable and non-toxic alternatives. This thesis focuses on the synthesis and characterization of non-isocyanate polyurethanes (NIPUs) derived from renewable sources, aiming to address the limitations of traditional PUs while enhancing their functional properties. Initially, NIPU foams were synthesized using xylose and dimethyl carbonate, with citric acid serving as a bio-based crosslinker. This innovative approach not only reduced the dependency on fossil fuels but also improved the flame retardancy of the foams under mild reaction conditions. The foams exhibited superior thermal stability and mechanical properties, as evidenced by comprehensive characterization techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). Building on this, the synthesis methodology was further refined through a one-pot process, eliminating the need for sophisticated reaction setups and harsh conditions. This simplification aimed to make the production of porous NIPU materials more scalable and environmentally friendly. The resulting materials demonstrated enhanced flame retardancy and structural integrity, confirmed by solid-state NMR and Powder X-ray Diffraction (PXRD) analyses. The research then progressed to the development of NIPU blends with poly(vinyl alcohol) (PVA), focusing on their rheological, thermal, and mechanical properties. These blends exhibited unique viscoelastic behavior and improved thermal stability, highlighting their potential for advanced material applications. The study of these blends was pivotal in understanding the interactions between NIPU and PVA, providing insights into the design of sustainable polymer composites. ix ix Furthermore, the thesis explored the synthesis of NIPU-based hydrogels for environmental and biomedical applications. Utilizing water as a solvent, these hydrogels were synthesized under mild conditions, overcoming the challenges posed by traditional methods that require organic solvents. The hydrogels demonstrated remarkable efficacy in dye removal, achieving high removal efficiencies for crystal violet and malachite green dyes. Additionally, their potential for drug delivery was investigated using cefadroxil as a model drug, showcasing their capability to effectively release pharmaceutical agents. Overall, this research presents a comprehensive study on the synthesis, characterization, and application of NIPUs derived from renewable sources. It highlights the feasibility of producing environmentally friendly and high-performance polyurethanes, paving the way for future developments in sustainable materials. The findings of this thesis contribute significantly to the field of polymer science, offering innovative solutions to the challenges posed by conventional PUs and opening new avenues for their application.