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.

Automated summary

This study investigates the effect of different chain extenders on the structure-property relationships of soy-based polyurethanes during hydrolytic degradation. It is found that the addition of chain extenders accelerates the degradation of flexible domains, resulting in a stiffer and more brittle polymer. Hydrolytic degradation also leads to the formation of new infrared absorption peaks and increased phase separation.