The role of hard and soft segments in the thermal and mechanical properties of non-isocyanate polyurethanes produced via polycondensation reaction

Plenty of research is being conducted on non-isocyanate polyurethanes (NIPUs) to replace harmful diisocyanates in traditional polyurethanes (PUs). In this research, the role of different types of hard and soft segments was investigated in the production of NIPUs via the polycondensation route. Hard segments comprised ethylene carbonate or propylene carbonate with hexane-1,6-diamine, while the soft segments consisted of polyethylene glycol (1000 g/mol or 400 g/mol) or polypropylene glycol (1000 g/mol) and were polymerized in different molar ratios. The NIPUs were characterized for their thermal and mechanical properties. FTIR and solvent resistance to THF was used to evaluate the polycondensation reaction. Thermal analysis revealed mainly mixed hard and soft segments; the selection of the hard segment had an impact on the crystallinity of the mixed phase. Promising cohesive strength results as well as lap shear strengths were found on stainless steel and beech when the right selection of components was used. The best results were achieved when propylene carbonate was used as the hard segment, and polypropylene glycol (1000 g/mol) as the soft segment precursor in 1:30 molar ratio.