Effect of chain extenders on the hydrolytic degradation of soybean polyurethane

This publication highlights the effect that different chain extenders (CEs) have on the structure-property relationships of soy-based polyurethanes that have been exposed to hydrolytic degradation for 480 and 960 h at 80 degrees C. Gel content, crosslinking densities, surface energy, atomic force microscopy, dielectric, and dynamic mechanics were used for monitored structural changes. Polyurethanes (PU) is composed of a structure with minor phase separation when a chain extender is not used, maintaining all properties over time. However, when a chain extender, butane-1.4-diol (BDO), ethane-1.2-diol (MEG) our (2-hydroxypropoxy)-propane-2-ol are added, it is noted that there is a more significant degradation in the flexible domains, modifying the fraction between the initial rigid (HS)/soft (SS) segment that makes the polymer stiff and brittle. The hydrolysis degradation generates new Fourier transform infrared bands relative to urea (1640 cm(-1)) and amide (1800 cm(-1)). The reduction in band intensity of the C=O-free at 1730 cm(-1), while increasing the intensity of C=O-bonded at 1710 cm(-1) indicated a higher phase separation degree. After 960 h the T-gS decreased, while the T-gH was practically unchanged. The higher polarization observed in the PUs with BDO and MEG samples indicates the increased phase separation resulting in hydrolytic degradation.