Bismaleimide resins modified by an allyl ether of bio-based resveratrol with excellent halogen-free and phosphorus-free intrinsic flame retardancy and ultrahigh glass transition temperature

Abstract

Development of new allyl compounds to modify bismaleimide (BMI) resins for improving the toughness while maintaining a high thermal performance and flame retardancy is still urgent. In this study, we synthesized the allyl ether of resveratrol (AER), a bio-based allyl compound, to modify BMI resin. A series of BMI/AER resins (BA resins) were prepared by changing the molar ratio of BMI to AER. Compared with 2,2′-diallyl bisphenol A (DBA) modified BMI resins (BD resins), which has been widely used in industry, BA resins can be cured at a lower temperature. Although the toughness of cured BA resins was slightly inferior than that of cured BD resins, the cured BA resins exhibited much superior thermal performance and flame retardancy to the cured BD resins. For the BA-0.8 resin with a molar ratio of imide to allyl groups of 1:0.8, the glass transition temperature, thermal decomposition temperature of 5% weight loss, and char yield of the cured product were as high as 388 °C, 415 °C, and 48.6%, respectively. Meanwhile, the UL-94 and limit oxygen index (LOI) tests revealed an excellent flame retardancy of the cured BA-0.8 resin with V-0 level and LOI of 37.7%. The remarkable properties were attributed to AER with the tri-functionality and stiffness conjugated stilbene backbone giving the cured resins higher crosslinking density, chain rigidity and thermostability compared with DBA. This work provides a novel insight into the development of high-performance bismaleimide-based thermosetting resins with excellent halogen-free and phosphorus-free intrinsic flame retardancy.