Polyurethane based on modifi ed soybean oil
Authors:   Institute of Macromolecular Chemistry of the NAS of Ukraine, 48 Kharkivske Highway, Kyiv 02155, Ukraine, Robota Liudmyla , AKHRANOVYCH OLENA ,   Institute of Macromolecular Chemistry of the NAS of Ukraine, 48 Kharkivske Highway, Kyiv 02155, Ukraine, BRYKOVA OLEKSANDRA ,   Institute of Macromolecular Chemistry of the NAS of Ukraine, 48 Kharkivske Highway, Kyiv 02155, Ukraine, SAVELIEV YURII ,   Institute of Macromolecular Chemistry of the NAS of Ukraine, 48 Kharkivske Highway, Kyiv 02155, Ukraine
Published: December 2024

New polyurethanes with more than 70 % plant-derived polyol content were prepared using soybean polyol (SP) as a diisocyanate extender castor oil precursor, and aqueous dispersions using SP (1 and 5 wt.%) mixed with polyoxytetramethylene glycol (PF) as the polyester component. Soybean polyols reactive in urethane formation reactions were obtained by hydroxy functionalization of epoxidized soybean oil (ESO) with diethanolamine without the use of a catalyst. Comparative IR spectroscopic studies of their structure with the structure of the starting materials revealed incomplete amidation of ESO with preservation of the glycerol backbone and incomplete hydroxylation of oxirane fragments of ESO, leading to the formation of a mixture of polyols of appropriate composition and structure, which are chemically diethanolamidoamines of fatty acids of soybean oil (DEAAHSO). The physical-mechanical properties, water absorption level and resistance to alkaline and acidic environments of the polyurethanes obtained were studied as a function of SP content and the nature of diisocyanate. An increase in the SP content (0.1–0.75 wt.%) in PU based on hexamethylene diisocyanate (HDI) is accompanied by a decrease in both tensile strength from 8.3 to 3.2 MPa and elasticity with an increase in water absorption from 0.4 to 2.6%. The weight loss of PU with the increase of SP content in its composition decreases both in alkaline and acidic environments. Compared to PU based on HDI, its analog based on toluene diisocyanate (TDI) with a similar content (2.5 wt.%) of soybean polyol has improved properties due to the effect of the nature of the isocyanate and, according to the results of an IR spectroscopic study, an increased level of intermolecular association of its polar fragments. The tensile strength is 3.5 times higher than the analog and is 19.9 MPa with a 3.2-fold reduction in elasticity, and water absorption is 50% lower with no weight loss in aggressive environments. The film-forming, aggregation-stable aqueous PU dispersions containing 1–5 wt.% of soybean polyol in the oligomeric diol were prepared. The particle size of the dispersed phase increased from 74 to 212 nm with increasing SP content from 1 to 5%, and the tensile strength at 1 wt.% content increased almost twofold compared to the matrix and is 13.1 MPa. An increase in the SP content from 1 to 5 wt.% contributes to a decrease in water absorption, which is 2.4 times greater than that of the matrix and amounts to 6.4 wt.%, which may be a consequence of a disruption of the intermolecular interaction level. At the same time, the stability increases in the alkaline environment and decreases in the acidic environment. The factor regulating the level of hydrophobicity of the films surface made on the basis of IPU is the presence in their composition of amidoamines of fatty acids of soybean oil, the content of which is manifested by an increase in the indicators of contact angles of surface wetting, which are 64–67° in comparison with the matrix, where the indicator is 39°.