Kinetics behind a Strategy for Modulation of Sustainable Benzoxazines: Experimental Study and Its Theoretical Verification

Abstract

A series of benzoxazine monomers with varied benzoxazine functionality from 1 to 3 (mono, bis, and tris) is prepared by reacting agrowaste‐derived cardanol with higher functionality amines. The ring opening polymerization study of cardanol‐based benzoxazine monomers is investigated by three modes, namely, solution (nuclear magnetic resonance and gel permeation chromatography), bulk (differential scanning calorimetry), and theoretical (B3LYP and 6–31+G**) calculations to analyze the role of number of benzoxazine functionality in curing behavior of the monomers. It is found that the presence of higher and close vicinity of benzoxazine functionality in the monomer promotes faster ring opening, rapid polymerization conversion, and enhancement in the average molecular weight buildup. The activation energy for the curing process is found to decrease from 144–113 kJ mol−1 from mono‐ to tris‐benzo­xazine monomer. Thermodynamically, the presence of higher benzoxazine moiety reveals the curing process is highly exergonic as supported by theoretical calculations. Free energy for successive protonation varies from −9.54 to −24.68 eV for mono‐ to tris‐functionalized monomer. The effect of number of functionality in monomer on its curing behavior – a complete study is reported to offer sustainable monomers/polymers for futuristic materials applications.

Design of thermosetting polymeric systems based on benzoxazines modified with maleic anhydride

“…The IR spectrum of BzPOH is shown in Figure . The absorbance intensities at 3420 and 2960 cm − 1 corresponding to the stretching vibrations of hydroxyl and CH 2 groups are respectively observed, as well as the characteristic bands at 1500, 1260, and 935 cm − 1 attributed to the benzoxazine ring are detected . The band at 935 cm − 1 is related to the CO stretching of the oxazine ring and the phenolic ring vibrational modes, but it is mainly associated to oxazine ring .…”

“…The band at 935 cm − 1 is related to the CO stretching of the oxazine ring and the phenolic ring vibrational modes, but it is mainly associated to oxazine ring . Moreover, the absorbance intensities at 1260 and 1500 cm − 1 are attributed to the asymmetric COC stretching and to the tri‐substituted benzene ring, respectively . The 1 H and 13C‐NMR spectra of BzPOH and the assignment of each signal are shown in Figure .…”

Curing Process of Benzoxazine Systems. An Experimental and Theoretical Study

“…For this analysis, a fine suspension of the samples was dispersed in KBr, and then pressed to form transparent KBr pellets. The FTIR spectrum showed the characteristics bands of the Bzs at 945 and 1500 cm -1 associated to the oxazine ring and to the tri-substituted benzene ring, respectively (Shukla et al, 2016;Han et al, 2017). A further band of interest was identified at 752cm -1 attributed to the N-CAr stretching (Soto et al, 2016).…”

Cardanol and Eugenol Sourced Sustainable Non-halogen Flame Retardants for Enhanced Stability of Renewable Polybenzoxazines

“…The characteristic peaks at ∼1,240 and 1,041 cm −1 corresponding to the asymmetric and symmetric stretching of C-O-C due to benzoxazine ring in C-trisapm and undergoes ring-opening FIGURE 4 | 31 P NMR spectra of EP and N 3 P 3 Cl 6 (Solvent: CDCl 3 ). reaction, which is initiated when heated at ∼200 • C ≥ 2 h (Shukla et al, 2016). Due to significant overlap of former stretch with phosphazene core vibrations, it cannot be monitored in the blends with CP/EP.…”