Effects of Primary Aromatic and Primary Aliphatic Amines on the Formation of Cardanol-Based Benzoxazine Monomers Based on Fourier-transform Infrared and Raman Spectroscopy

High-performance benzoxazine monomers are presenting an interesting challenge in polymer science. The demand for natural phenols, such as cardanol is growing due to shrinking petroleum resources and rising concerns about environmental sustainability. This analysis examines the effects of aromatic and aliphatic amines on the formation of cardanol-based benzoxazine monomers. During the analysis, four benzoxazine precursors prepared from cardanol-aniline (C-an), cardanol-furfurylamine (C-fu), cardanol-laurylamine (C-la), and cardanol-stearylamine (C-sa) were separately reacted with paraformaldehyde via a Mannich condensation reaction mechanism. The functional groups and crystallinity degree of the benzoxazine monomers were investigated using nonlinear Gaussian deconvolution of the fourier transform infrared (FTIR) and Raman spectra. The results indicated cardanol-based benzoxazine synthesized with furfurylamine contained a higher number of oxazine rings than that with aniline, laurylamine, and stearylamine. The Raman spectral analysis showed that the double bond in the carbon structure of the furan ring derived from furfurylamine occurred at the Raman shift of 1505 cm-1. Consequently, the double bond in the carbon structure of the benzene ring originated from aniline and occurred at the Raman shift of 1600 cm-1. The benzoxazine monomer synthesized with furfurylamine showed a degree of crystallinity of 54.49%, signifying a higher number of benzoxazine molecules due to the reactivity of the furan rings in the oxazine ring formation process.