One-pot synthesis of polyurethane-imides with tailored performance from castor and tung oil

Abstract

Herein, castor and tung oil-based polyurethane-imides with tailored thermal and mechanical performance were developed by a one-pot method. First, tung oil (TO) was transformed into eleostearic acid diethanol amide (EADEA) by methyl-esterification and amidation. The resulting EADEA was then mixed with castor oil (CO), N-(2-hydroxyethyl)-maleimide (HEMI) and isophorone diisocyanate to prepare biobased polyurethane-imides. The formation of Diels-Alder (DA) adducts from EADEA and HEMI during the curing process was determined by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The effect of DA adducts contents on the thermal and mechanical properties of corresponding polymers was investigated. The results show that the introduction of TO-maleimide DA adducts significantly increases the glass transition temperature, tensile strength, Young’s modulus and gel content of the resulting polyurethanes. The highest tensile strength of the resulting polymers can reach 48.2 MPa. Besides, the thermal stability was also improved with the incorporation of imide groups. This technique reported here demonstrates several advantages, such as one-pot synthesis, high bio-renewable content, low cost and tunable performance, and it is promising to find application in coatings, adhesives and so on.