Synthesis and Characterization of Cyanate Ester Functional Benzoxazine and Its Polymer

Abstract

The first benzoxazine incorporating cyanate ester group in its structure has been synthesized. The polymerization process investigated by differential scanning calometry (DSC) exhibits two clearly separated exotherm maxima, corresponding to cyanate ester trimerization and benzoxazine, respectively. The nature of each exotherm is studied by Fourier transform infrared spectroscopy (FT-IR). The activation energies for cyanate ester trimerization and benzoxazine ring-opening polymerization are determined by both Kissinger's and Ozawa's methods. Furthermore, both exothermic temperatures observed are lower than those of the published values of benzoxazine and dicyanate ester blends. Thermal properties such as glass transition temperature and char yield are studied by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Those properties are found to be outstanding compared to the reported properties of general benzoxazine resins and polymerized blends of benzoxazine and dicyanate ester, offering a polymeric matrix for composite satisfying many requirements for such a material.

Biobased Benzoxazine Derived from Daidzein and Furfurylamine: Microwave‐Assisted Synthesis and Thermal Properties Investigation

“…Usually,t he peak temperaturei nt he DSC exothermic curve is taken as an indicatort oe valuate the curing reactivity.T he lower the temperature of the peak, the highert he reactivity of the system. Based on the literature survey, [5] the exothermic peak standing for the typical oxazine ring opening polymerization was usually observed at 240-260 8C. The relativelyl ower polymerization temperature of Dz-f might be due to the "cooperativea ctivation effect" of benzopyrone and furan, which was also reported in previous work.…”

“…[1][2][3] Nevertheless, traditional polybenzoxazine has demonstrated obviouss hortcomings, such as ah igh curing temperature, relativelyl ow crosslink density,a nd high brittleness. [4,5] To improve their performance, the design and synthesis of multifunctional benzoxazine precursors is the usual strategy.T he bisphenolc ompounds, such as bisphenol A, [6] bisphenol F, [7] and bisphenol S [8] were the commonr aw materials for benzoxazines ynthesis. Aside from this, the additional polymerizable functional groups, including allyl, [9] acetylene, [10] benzocyclobutene, [11] maleimide, [12] norbornene, [13] andc yanate ester, [14] have also been introduced into the molecular architectures to further improve their properties.…”

Examining the effect of hydroxyl groups on the thermal properties of polybenzoxazines: using molecular design and Monte Carlo simulation

“…Polybenzoxazines are a class of thermosetting phenolic resins that gained great interest because of their unusual set of competitive properties. [1][2][3][4][5][6] They combine various outstanding properties of high performance thermosets like high thermal stability, 7 high char yield, 8 high glass transition temperature (T g ), 9 near-zero volumetric change during polymerization, 10 good mechanical 11 and dielectric properties, 12,13 low water absorption 14 and low ammability. 15 The most attractive characteristic of polybenzoxazines is their extraordinarily rich molecular design exibility and versatility in molecular structure.…”

Synthesis of novel tri‐benzoxazine and effect of phenolic nucleophiles on its ring‐opening polymerization

“…Various efficient catalytic systems have been employed to fasten the ring‐opening polymerization at low temperature, mainly includes Lewis acids such as metal halides, acetylacetonato complexes of transition metals of the fourth period, p ‐toluene sulfonates, and so forth; however, in most cases, a complete conversion was achieved only by heating from 150 to 180 °C for several hours . Furthermore, development of benzoxazines with special side groups, such as carboxylic [curing maxima ( T p ): 180 °C], phenolic hydroxyl ( T p : 165 °C), methylol (ortho T p : 196 °C; para T p : 231 °C; meta T p : 214 °C), allyl (almost a complete conversion attained by heating at 150 °C for 10 h, whereas 22% unreacted remains in benzoxazine without allyl moiety), hydroxyethyl (complete conversion attained by heating at 150 °C for 6 h), formyl ( T p : 205 °C), cyanate ester ( T p : 213 and 229 °C), and so forth, has been reported to reduce the curing temperature of monofunctional benzoxazine ( T p : 261 °C) to some extent, due to their catalytic nature on cationic ring‐opening polymerization of oxazine. However, a bifunctional benzoxazine still requires a high temperature for a complete polymerization (200–250 °C) even with such end groups …”