Synthesis and characterization of a novel high-performance benzoxazine from benzaldehyde-based bisphenol

In this work, a new type of benzaldehyde-based bisphenol (BPBA) was successfully synthesized which in turn was converted into a structurally modified and moderately low-temperature-cure benzoxazine (BPBA-Bz) using three different amino compounds (aniline, allyl amine, and furfuryl amine) and formaldehyde at appropriate conditions. The molecular structure of these benzoxazines was confirmed by FTIR, H-1 NMR, and C-13 NMR. The curing behavior and thermal stability of the benzoxazines were analyzed using differential scanning calorimetric and thermogravimetric analysis, respectively. Data obtained from thermal analysis infer that the synthesized benzoxazines were found to possess a comparatively lower cure temperature (T-p) and enhanced glass transition temperature (T-g), thermal stability, and char yield than those of conventional benzoxazines. In addition, the influencing effect of catalysts on the reduction in curing temperature of benzoxazines was studied with different phenolic compounds viz 4-hydroxyphenyl maleimide, imidazole core bisphenol, and monohydroxy imidazole (MHI) to utilize them in the form of adhesives, sealants, encapsulants, and matrices with other substrates for different applications. Among the different catalysts used, MHI was found to be the most efficient in reducing the cure temperature which brings down the polymerization temperature to 171 degrees C from 229 degrees C. Further, the effect of improvement of thermal stability and flame retardant behavior were studied by blending bismaleimide-based cross-linkers namely 4, 4 '-diaminodiphenylsulfone-based bismaleimide (BMI-S) and 4, 4 '-diaminodiphenylmethane-based bismaleimide (BMI-M). From the data resulted, it is concluded that the blends of structurally modified BPBA-based benzoxazines with BMI possess an significantly improved thermal stability and char yield than those of conventional benzoxazines and can be conveniently used in the form of encapsulants, sealants, adhesives, and matrices in the fields of automobile and microelectronic applications for better performance and improved longevity.