New polyurethanes containing cycloaliphatic units in the hard segments. The influence of the microstructure on the thermo-mechanical and surface properties

New linear and cross-linked polyurethanes with cycloaliphatic units and renewable cross-linkers (Span 20 and Tween 20) were obtained by two steps polyaddition reaction. The degree of microphase separation was calculated by FTIR-ATR spectroscopy with higher values for the linear polyurethane with the highest hard segment content (0.88) and lower values for the cross-linked polyurethane with Tween 20 as cross-linker (0.35). The results were in accordance with the DSC analysis. The linear or cross-linked character of the polyurethane structure influenced the thermal, mechanical, and surface properties. The obtained polyurethanes had good thermal stability, with a 5% mass loss at 321 degrees C (HMC 1) and 329 degrees C (HMC 2) for linear polyurethanes and 330 degrees C (HMC 3) and 342 degrees C (HMC 4) for the cross-linked ones. The morphology and wettability of the cycloaliphatic polyurethanes presented different behavior depending on the amount of the hard segment content and also the chemical structure of the cross-linker. Linear polyurethanes were characterized by a globular morphology and hydrophobic character, while the use of Tween 20 as cross-linker led to a fibrillar morphology with a low water contact angle (62 degrees). Mechanical measurements showed that all polyurethanes present elastomeric behavior with high tensile strength values for the linear polyurethanes (33 MPa for HMC 1 and 39 MPa for HMC 2) and lower values of tensile strength for the cross-linked ones (12 MPa for HMC 3 and 11 MPa for HMC 4), but high elongation at break for all samples (780%-1100%).