Synthesis and melt-spinning of partly bio-based thermoplastic poly(cycloacetal-urethane)s toward sustainable textiles

A rigid diol with a cyclic acetal structure was synthesized by facile acetalation of fructose-based 5-hydroxymethyl furfural (HMF) and partly bio-based di-trimethylolpropane (di-TMP). This diol (Monomer T) was copolymerized with potentially biobased flexible polytetrahydrofuran and diisocyanates to prepare thermoplastic poly(cycloacetal-urethane)s. A modified one step solution polymerization protocol resulted in relatively high molecular weights (M_n ~ 41.5 -98.9 kDa). All the obtained poly(cycloacetal-urethane)s were amorphous with tuneable glass transition temperatures up to 104 °C. Thermogravimetric analysis indicated that these polymers were thermally stable up to 253 °C and had a relatively high pyrolysis char residue, which may indicate potential inherent flame resistance. Melt rheology measurements were performed to determine a suitable processing window between 165-186 °C, after which the polymer was successfully melt-spun into ~150 meters of homogeneous fibres at 185 °C. The resulting fibres could be readily hydrolysed under acidic conditions, resulting in partial
recovery of the original chemical building blocks.