Attenuated total reflectance infrared (ATR-FTIR) spectroscopy was used to characterize the functional groups of the synthesized STPUs and also to investigate the hydrogen-bonding formation.
DSC thermograms of the synthesized STPUs and the PTEG were obtained on a Mettler Toledo DSC 822e calorimeter by cooling the sample from room temperature to -100[degrees]C by liquid nitrogen and then heating the sample to 250[degrees]C at a heating rate of 20 [degrees]C/min, under an inert nitrogen atmosphere.
It is known that in MDI-based STPUs the free carbonyl groups of the urethane bond show absorbance bands at 1731-1733 [cm.
In the absorption range of carbonyl group (C=0), the urethane carbonyl band appears at different wavenumbers, depending on whether the free electron pair of the amine group is conjugated with the [pi] bond of the carbonyl group in HDI-based STPUs (1682 [cm.
In general, synthesized STPUs showed properties comparable to petroleum derived polyurethanes [28, 36].
The effect of the different STPUs microstructure on their macroscopic behavior is also reflected in their hardness.