Rational design and synthesis of novel benzoxazine resins with excellent thermal and flame - Retardant properties

Benzoxazine resins, a type of thermosetting resin, have drawn increasing research attention due to their advantages in flame retardancy, heat resistance, and waste - free curing. However, balancing multiple advantageous properties like high residual carbon content, low curing temperature, and excellent flame retardancy remains a challenge in their application. In this study, four benzoxazine resin materials were rationally designed and synthesized using inexpensive and readily available 2,4 - dihydroxybenzaldehyde as the starting material. Among them, Poly(EHD – 3apa) stands out with remarkable performance. It has a low curing temperature of 186.1 °C, which can be attributed to the catalytic effect of hydroxyl and aldehyde groups in its structure. Poly(EHD – 3apa) also exhibits high thermal stability, with a heat resistance index (HRI) value of 284, and a high char yield of 67 %. Its outstanding flame retardancy is demonstrated by an LOI value of 40, well above the self - extinguishing material standard. MCC testing and vertical burning tests further confirm its excellent flame - retardant properties. These results indicate that Poly(EHD – 3apa) shows great potential for applications in high - performance composite materials.