Synthesis and Characterization of Low-Cost Cresol-Based Benzoxazine Resins as Potential Binders in Abrasive Composites

Abstract

<jats:p>A series of cresol-based benzoxazines were synthesized for potential application as a polymer matrix in abrasive composites. The chemical structures of the obtained benzoxazine resins were investigated in detail using Fourier transform infrared spectroscopy (FTIR) and hydrogen-1 as well as carbon-13 nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR) with an additional analysis using two-dimensional NMR techniques (2D NMR 1H-1H COSY, 1H-13C gHSQC and gHMBC). Structural analysis confirmed the presence of vibrations of -O-C-N- at ~950 cm−1 wavenumber, characteristic for an oxazine ring. The thermal properties of benzoxazine monomers were examined using differential scanning calorimetry (DSC) analysis. The polymerization enthalpy varied from 143.2 J/g to 287.8 J/g. Thermal stability of cresol-based benzoxazines was determined using thermogravimetry (TGA) analysis with additional analysis of the amount of volatile organic compounds (VOC) emitted from the synthesized benzoxazines during their crosslinking by static headspace coupled with gas chromatography technique (HS-GC). The amount of residual mass significantly differed between all synthesized polybenzoxazines in the range from 8.4% to 21.2%. The total VOC emission for benzoxazines decreased by 46–77% in reference to a conventional phenolic binder. The efficiency of abrasive composites with the benzoxazine matrix was evaluated based on abrasion tests. Performed analyses confirmed successful synthesis and proper chemical structure of cresol-based benzoxazines. All the experiments indicated that benzoxazines based on different cresol isomers significantly differ from each other. Good thermal performance and stability of the abrasive composites with the polybenzoxazine matrix and significantly lower VOC emission allow us to state that benzoxazines can be a promising and valuable alternative to the phenolics and a new path for the development of modern, eco-friendly abrasives.</jats:p>

Surface Modification of Kombucha Bacterial Cellulose for High Water and Water Vapor Barrier: Enhanced Properties through Enzyme Etching and Cardanol‐Silane Coating

“…Furthermore, the presence of benzene ring vibration in CBS was detected at 752 cm À1 , and transmittance band of benzene at 960 cm À1 , showing EKBC was successfully coated, which is consistent with results reported by Zakirov et al [41] In contrast, due to KBC low solubility in most of the common solvents, FTIR spectrum of cured CBS was used to study the ring-opening effect instead; transmittance peak at 950 cm À1 disappeared, indicating the ring opening of oxazine ring (O-C-N). Likewise, peaks at 1230 and 1630 cm À1 representing C─O─C bonds reduced; overall, crosslinking between CBS can be seen and the curing results are similar with Jamrozik et al [42] Feng et al [43] and Zhu et al [44] Through SEM-EDX, increment in silica and carbon was observed, showing that carbon-rich CBS was attached to the surface of EKBC elementally (Table 1). The increase in coating concentration increased the amount of nitrogen, carbon, and silica but the amount of oxygen only subtly changed comparing the surface of 2% and 4% CBS/KBC, suggesting that although more CBS is available for adhesion, hydroxyl groups on KBC surface are not evenly available.…”

Improved dispersion of reduced graphene oxide in benzoxazine composites via electrostatic interaction with M‐cresol

“…Multiples of aromatic protons were detected between 6.63 and 7.27 ppm. [ 16 ] The proton peaks of in‐situ synthesized rGO/mC‐A are identical to the 1 H‐NMR spectra of the solution blending rGO/mC‐A system (Figure 1G) and pure mC‐A (Figure S3). These results indicate that the interaction between m‐cresol and rGO does not affect the synthesis of the benzoxazine monomer, that the in‐situ synthesis of rGO/mC‐A can be achieved, and that there is no electrostatic interaction between the benzoxazine synthesized in‐situ and rGO.…”

“…The FT‐IR spectra of the in‐situ synthesized rGO/mC‐A (Figure 2D) after each curing cycle were compared to those of solution mixed rGO/mC‐A (Figure S6A) and pure mC‐A (Figure S6B). In the spectra of the in‐situ synthesized rGO/mC‐A (Figure 2D), the characteristic absorption bands at 947 cm −1 (CON vibration), 1030 and 1243 cm −1 (symmetric and antisymmetric vibration of COC), and at 1495 cm −1 (characteristic peak of benzene ring) [ 16 ] gradually decreased after 1 h of curing from 160°C, indicating the ring‐opening reaction of mC‐A.…”

Lignin-Based Water-Soluble Polymers Exhibiting Biodegradability and Activity as Flocculating Agents

“…The crosspeaks of K 1 and K 7 represent methylene linkages connecting the α-aminoand ε-amino groups of L-lysine, respectively, to the aromatic rings in lignin, and their presence indicates that both amino groups in L-lysine participate in the Mannich reaction. The NMR spectra for K-pine (Figure 3b) and K-corn stover (Figure 3f) also include the cross-peaks characteristic of benzoxazines, 51,52 B α , as shown in green. These heterocyclic structures can be produced from the condensation of the amino groups of the grafted L-lysine, aromatic hydroxyl groups, and residual, unreacted formaldehyde.…”