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Modification of Solventless‐Synthesized Benzoxazine Resin by Phthalonitrile Group: An Effective Approach for Enhancing Thermal Stability of Polybenzoxazines
Author(s) -
Liu Yuqi,
Yin Ren,
Yu Xinye,
Zhang Kan
Publication year - 2019
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201800291
Subject(s) - phthalonitrile , thermogravimetric analysis , thermal stability , differential scanning calorimetry , polymer chemistry , fourier transform infrared spectroscopy , materials science , polymerization , epoxy , maleimide , chemical engineering , chemistry , polymer , organic chemistry , composite material , physics , phthalocyanine , engineering , thermodynamics
Although the solventless method for synthesizing benzoxazine resins has the advantage of low cost, the impurities involved in the products such as oligomers and original phenols significantly weaken the properties of polybenzoxazines. Herein, the commercialized BA‐a (benzoxazine derived from bisphenol‐A, aniline, and formaldehyde) resin obtained from a solventless method is modified by phthalonitrile through the reaction between phenol groups and 4‐nitrophtahlonitrile. The structures of obtained resins have been confirmed by 1 H and 13 C nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR). In addition, the ring‐opening polymerization behavior of each resin has been studied by differential scanning calorimetry and in situ FTIR. Furthermore, the thermal properties of the cross‐linked thermosets were measured by thermomechanical analysis and thermogravimetric analysis. The phthalonitrile‐functionalized benzoxazine resin shows a low polymerization temperature with the maximum of exothermic peak centered at 218.7 °C, and its corresponding polybenzoxazine exhibits excellent thermal stability, with a high Td 5 value (346 °C) and high char yield (42.78%).