Bio-based hydrophobic epoxy-amine networks derived from renewable terpenoids

Carvacrol and p-cymene are sustainable and versatile starting materials for the preparation of hydrophobic monomers. These molecules can be readily derived from pine resin or produced from other sustainable feedstocks via a biosynthetic approach. A hydrophobic epoxy monomer [bis(2-isopropyl-5-methyl-4-(oxiran-2-ylmethoxy)phenyl)methane, 3] with methyl and isopropyl substituents on the aromatic rings was synthesized from carvacrol. A bisaniline [4,4'-methylenebis(5-isopropyl-2-methylaniline, 4] was then synthesized from p-cymene. Using a cured epoxy-amine network prepared from the diglycidyl ether of bisphenol A (DGEBA) and 4,4'-methylenedianiline (MDA) as a baseline system, three additional networks were prepared from DGEBA:4, 3:MDA, and 3:4. The cured epoxy-amine networks were tested for moisture uptake as well as changes in thermomechanical properties after exposure to boiling water for several days. Incorporation of the bio-based monomers resulted in up to 53% lower water uptake compared to the baseline system. The bio-based resins also showed greater resistance to degradation under hot-wet conditions, with wet-T-G knock-downs as low as 8% as compared to a 19% decrease for the baseline system. These results show that the unique functionality of the renewable bisphenol and aniline used in this study can result in materials with improved hot/wet performance as compared to conventional thermosetting resins. (C) 2016 Wiley Periodicals, Inc.