Preparation of a flame-retardant epoxy curing agent based on castor oil and study on the curing reaction kinetics

摘要

A novel bio-based binary acid for flame-retardant epoxy curing agent named ricinoleic acid modified with itaconic anhydride (IDDRA) was synthesized from castor oil via glycidylation, epoxy ring-opening reaction and esterification. Its chemical structure was characterized by FTIR and H-1-NMR. In order to improve the rigidity of its epoxy cured products, we prepared a series of mixed curing agents by mixing it with certain proportions of methyl nadic anhydride containing rigid groups, and then these mixed curing agents were used to cure E51 epoxy resin at certain temperature. The curing behavior of the cured materials was studied using differential scanning calorimetry. The tensile property, limiting oxygen index (LOI) and dynamic mechanical thermal properties of cured materials were all investigated. The cured epoxy materials had a relatively high tensile strength up to 34.21 MPa, and the elongation at break was up to 400.01%. The LOI values increased from 22.5 to 23.8% with the increase in IDDRA content. Dynamic mechanical analysis showed that the glass transition temperature decreased from 60.40 to 17.33 A degrees C with the increase in IDDRA content, which indicated IDDRA could improve the toughness of epoxy cured products. Curing behaviors of the IDDRA/E51 curing system were studied by using differential scanning colorimetry at different heating rates, and the curing reaction parameters were optimized by extrapolation method. The results showed that the optimized curing process conditions of the curing systems were 130 A degrees C/2 h + 160 A degrees C/3 h, and the curing degree could achieve 86.40% within 15 min at 130 A degrees C.