New bio-based thermoplastic polyurethane elastomers from isosorbide and rapeseed oil derivatives

Thermoplastic polyurethanes (TPUs) from fatty acids dimer-based polyester polyols, 4,4'-methylene bis(phenyl isocyanate) (MDI) and isosorbide (ISO) as chain extender were successfully synthesized by a two-stage synthesis. TPUs obtained from isosorbide were compared to the model 1,4-butanediol (BDO)-based materials. Differential scanning calorimetry revealed the phase-separated structure of these materials that displayed a typical thermoplastic elastomer behavior by dynamic mechanical analysis. Samples were further analyzed by transmission electronic microscopy, atomic force microscopy and compression set; hardness and water uptake were also monitored. Isosorbide was found to slightly increase the glass transition and melting temperatures of MDI-based hard segments, and to slightly decrease the stability and quality of phase segregation. This resulted in an increase in rubber modulus and hardness, shape retention, in a slight increase in the temperature of the a relaxation of the soft segment domains and in a characteristic microphase morphology. Moreover the use of the rather hydrophobic fatty acid-based soft segment allowed to keep the water uptake at a rather low level, in spite of the presence of isosorbide in the formulation.