Relationship between morphology, properties and degradation parameters of novative biobased thermoplastic polyurethanes obtained from dimer fatty acids

Biobased thermoplastic polyurethanes (TPUs) obtained from dimer acid-based polyols, 4,40-diphenyl- methane diisocyanate and 1,4-butanediol were synthesised by using a two-step prepolymer process. The effect of dimer acid-based polyols on the processing parameters was investigated. A full thermal, mechanical and thermo-mechanical characterisation of TPUs synthesised with different hard segment (HS) contents was also carried out. Thermogravimetric analysis showed the presence of three degra- dation steps which varied between the different TPU structures depending on the HS content. Colour tests showed substantial differences between TPU samples which were related to degradation param- eters. Initial degradation temperatures were lower than the polyol’s one and decreased with increasing HS contents. Tensile tests showed high deformation at break for these elastomeric TPU samples, except for the sample with 40 wt% of HS. Finally, rheology studies revealed that the melting temperature generally decreased with higher HS contents.