An investigation on new high performance Schiff base polyurethanes

Abstract

Novel poly(urethane-azomethine-thiourea)s (PUATs) were synthesized via one-step polymerization from newly prepared diol chain extender (1,4-phenylene bis((E)-1-(4-hydroxobenzylidene)thiourea) (PBHBT)), containing C=S and –C=N– linkages, along with 1,4-phenylene diisocyanate (PDI) as hard segments and 20, 40 and 60 mol.% polyethylene glycol (PEG) forming soft segments. The prepared chain extender and polymers were characterized via elemental, Fourier transform infrared, 1H- and 13C-NMR analyses, and physical properties such as ηinh, solubility, crystallinity, flame retardancy and thermal stability were studied. According to X-ray diffraction patterns, the Schiff base polymers exhibited amorphous morphologies and their molar masses were in the range of 148 × 103–163 × 103 g mol−1. Thermogravimetric analysis indicated that PUATs with 20 and 40 mol.% PEG were fairly stable above 500°C having T10 of 511–527°C and had high glass transition temperatures about 249–251°C. In comparison with typical polyurethanes, PUATs with lower polyol content exhibited better non-inflammability, Tg values, chemical and thermal stability owing to rigid hard segment structure.