Investigation of processing, thermal, and mechanical properties of a new composite matrix‐benzoxazine containing aldehyde group

A new benzoxazine aldehyde group containing monomer 3‐phenyl‐6‐formyl‐3, 4‐dihydro‐2H‐1, 3‐benzoxazine (Ald‐B) was synthesized via the Mannich reaction of formaldehyde, p ‐hydroxybenzaldehyde, and aniline. The viscosities and curing behavior of the resins were studied. The results indicated that Ald‐B has an initial viscosity lower than 0.110 Pa s at 90°C and the maximum temperature of the exotherm was at 196°C. Dynamic mechanical analysis (DMA) of the copolymer of Ald‐B and methylenedianiline‐type bis‐benzoxazine (B‐BOZ) showed only one T g of 251°C and high crosslink density in the matrix. The thermal stability of the copolymer was improved noticeably and the char yield at 800°C is 68.4%. The tensile strength and flexural strength of this resin cast are 72 and 137 MPa, respectively.