Biobased thermosetting resins composed of L‐lysine methyl ester and bismaleimide

Abstract

ABSTRACTLysine methyl ester (LME), which was generated in situ by the reaction of lysine methyl ester dihydrochloride and triethylamine in dimethyl sulfoxide (DMSO), was prepolymerized with 4,4′‐bismaleimidodiphenylmethane (BMI) at 80°C for 2 h in DMSO. Then, the formed prepolymer was precipitated in water. The obtained LME/BMI prepolymers with molar ratios of 2:2, 2:3, and 2:4 were compression‐molded at a final temperature of 230°C for 2 h to produce cured lysine methyl ester/4,4′‐bismaleimidodiphenylmethane resins (cLBs; cLB22, cLB23, and cLB24, respectively). Fourier transform infrared (FTIR) analyses revealed that the Michael addition reaction of amino groups to the CC bonds of the maleimide group occurred in addition to the homopolymerization of the maleimide group. The glass‐transition temperature (Tg) and 5% weight loss temperature (T5) of the cured resin increased with increasing BMI feed content, and cLB24 showed the highest Tg (343°C) and T5 (389°C). The flexural strengths (131–150 MPa) and moduli (3.0–3.6 GPa) of the cLBs were comparable to those of the conventionally cured resins of BMI and 4,4′‐diaminodiphenylmethane. Field emission scanning electron microscopy analysis revealed that there was no phase separation for all of the cured resins. Although cLB23 and cLB24 were not biodegradable, cLB22 had a biodegradability of 8.5% after 30 days in an aerobic aqueous medium containing activated sludge. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40379.