Silicon-containing trifunctional and tetrafunctional cyanate esters: Synthesis, cure kinetics, and network properties

Abstract

The synthesis and physical properties of new silicon-containing polyfunctional cyanate ester monomers methyl[tris(4-cyanatophenyl)]silane and tetrakis(4-cyanatophenyl)silane, as well as polycyanurate networks formed from these monomers are reported. The higher crosslinking functionality compared to di(cyanate ester) monomers enables much higher ultimate glass transition temperatures to be obtained as a result of thermal cyclotrimerization. The ability to reach complete conversion is greatly enhanced by cocure of the new monomers with di(cyanate ester) monomers such as 1,1-bis(4-cyanatophenyl)ethane. The presence of silicon in these polycyanurate networks imparts improved resistance to rapid oxidation at elevated temperatures, resulting in char yields as high as 70% under nitrogen and 56% in air in the best-performing networks. The water uptake in the siliconcontaining networks examined is 4-6 wt % after 96 h of immersion at 85 C, considerably higher than both carbon-containing and/or di(cyanate ester) analogs. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 767-779

Organic Crystal Engineering of Thermosetting Cyanate Ester Monomers: Influence of Structure on Melting Point

“…This dicyanate is one of the most widely studied, and the sample in our laboratory was consistent with the previously reported melting point of 356.0 ± 0.2 K, heat of fusion of 100 ± 9 J/g, and purity of 99.2 - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 6 99.4%. 27 These results are in general agreement with other studies. 5, [16][17][18][19][20][28][29][30][31][32][33][34] The siliconcontaining analog of BADCy, bis(4-cyanatophenyl)dimethylsilane, or SiMCy, was synthesized in our laboratory according to a previously published procedure 27 that closely follows the original synthesis reported by Wright.…”

“…27 The silicon-containing analog of ESR-255, tris(4-cyanatophenyl)methylsilane, also known as SiCy-3, was synthesized at AFRL with a reported melting point of 391.3 ± 0.1 K, heat of melting of 74 ± 2 J/g, and purity of 99.21 ± 0.04%. 27 Scheme 1 shows the chemical structures for BADCy, SiMCy, ESR-255, and SiCy-3. while the other is only available in printed form.…”

Bis-phenylethynyl polyhedral oligomeric silsesquioxanes: new high-temperature, processable thermosetting materials

“…1 A continuous service temperature of 370 C is widely recognized as a very important technical challenge for organic matrix composites. 2 Some thermosetting systems, such as polycyanurates, 3,4 poly-(benzoxazines), 5 and phenylethynyl-endcapped poly-(oligoimides) 6 have approached that benchmark, but few resins possess the requisite combination of processability, mechanical properties, and thermo-oxidative stability. Those that can be utilized in service over 300 C have nite lifetimes, especially in the presence of oxidizing species, and exhibit poor processability, requiring solvents for ber impregnation and high pressures to promote ow.…”

Thermal and oxidative behavior of a tetraphenylsilane-containing phthalonitrile polymer

“…15,23 The inclusion of silicon linkages has been reported to improve oxidative stability and flammability of high-temperature polymers. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] As oxygen and free radicals cleave carbon-silicon (C-Si) bonds, siloxy units are formed. These siloxy moieties may interact to produce an inert phase, which can reduce the rate of degradation of the surface and the rate of diffusion of oxygen into the bulk.…”

“…[50][51][52] Silicon linkages have also been incorporated in other high-temperature materials. Specifically, the addition of silicon linkages has been shown to improve the oxidative stability of polymers similar to phthalonitriles, including cyanate esters [24][25][26] and polyimide materials. [29][30][31][32][33][34][35][36][37][38][39] In many of these polymers reported in literature, the silicon linkage is attached to the aromatic backbone via a methylene bridge.…”