Bio-based epoxy networks incorporating covalent and melamine cyanurate-type multiple hydrogen-bonding crosslinkages

Prepolymerizations of polyglycidyl ether of polyglycerol (PGPE) with equimolar amounts of melamine (ML) and isocyanuric acid (iCA) at 80 degrees C and subsequent compression molding at 130-190 degrees C yielded cured PGPE/ML/iCA resins with epoxy/active hydrogen ratios of 1/3, 2/3 and 3/3 (PGPE-MC13, 23 and 33). Their properties were compared with the PGPE cured with ML or iCA with an epoxy/active hydrogen ratio of 1/1 (PGPE-ML or PGPE-iCA). Transparency of the cured resins became worse with increasing multiple hydrogen-bonding melamine cyanurate (MC = ML + iCA) fraction. The FT-IR analysis revealed that the epoxy groups were almost consumed for all of the cured resins, and the hydrogen bonding interaction became stronger with increasing MC fraction. Although glass transition temperatures (T(g)s) of PGPE-MCs were a little lower than those of PGPE-ML and PGPE-iCA, the T-g increased with MC fraction. The 5 % weight loss temperatures of PGPE-MCs were much higher than those of PGPE-ML and PGPE-iCA. The flexural modulus for PGPE-MCs increased with increasing MC fraction, and PGPE-MC13 exhibited the highest flexural modulus among all of the cured resins.