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Synthesis, characterization, and thermal properties of cyanate esters with azo linkages



A series of azo functionalized diols were synthesized through diazotization which involves the reaction of amine with phenol and 2,6-dimethyl phenol. Four different amines have been used to prepare five bisphenols. These bisphenols were converted to their corresponding cyanate esters by treatment with cyanogen bromide (BrCN) in the presence of triethylamine (Et3N). The chemical structures of the prepared compounds were characterized with Fourier Transform Infrared, 1H-NMR, 13C-NMR spectroscopy, and elemental analysis. Dynamic curing behavior was investigated using differential scanning calorimetry. The maximum curing temperature of these cyanate esters are in the range of (186–208°C). Tg values of the polycyanurate networks are in the range of 245–276°C. The thermal properties of cured cyanate ester were studied at a heating rate of 10°C min−1 in N2 atmosphere. The polymers showed excellent thermal stability (T10 was found to be in the range 405–438°C) and the percentage of char yield at 800°C were found to be 30–49. The flame retardancy of the cyanate ester resins have been studied using limited oxygen index value which is in the range of 29.5–37.1 at 800°C. POLYM. ENG. SCI., 55:47–53, 2015. © 2014 Society of Plastics Engineers