A RESEARCH GAP FRAMEWORK FOR NON-ISOCYANATE POLYURETHANES WITH INDUSTRIAL FOCUS

Abstract

This thesis describes a study of Non-Isocyanate Polyurethanes (NIPUs), which are a next generation sustainable polymer. It replaces conventional isocyanate-based polyurethanes. It discusses the reaction mechanisms of NIPU formation, such as cyclic carbonate aminolysis, transurethanization, ring-opening polymerisation, and carbon dioxide-epoxide (CO2 epoxide) coupling and then addresses the kinetic behaviour, catalyst design and structure-property relationship of NIPU formation. Advanced material architectures such as waterborne dispersions, epoxy/NIPU hybrids, UV-curable systems, and self-healing vitrimers are also critically analysed for their mechanical, thermal, and dynamic performance. Two unresolved industrial challenges, which are foaming window control and closed-loop recycling, are analysed through comparative studies of aromatic versus aliphatic cyclic carbonates and multi-dynamic bond networks (disulfide, imine, acetal) which enable solvent-free recyclability. The thesis further highlights toxicological profiles, circular-economy integration, and bio-composite development using natural fibres (jute, flax, hemp, bamboo) which are reinforced with bio-based NIPU matrices. Finally, three conceptual innovations are proposed: a Reactive CO₂ Dual-Function (RCDF) platform for simultaneous carbon fixation and polymerisation, lignin-derived bifunctional carbonate macromonomers for high-performance coatings, and NIPU-based bio adhesive hydrogels for wound closure and tissue repair. Collectively, this work forms a basis for a combined approach for transitioning NIPU chemistry from laboratory synthesis to scalable, circular, and non-toxic industrial applications.