Synthesis and characterization of cyanate ester and its blends with bisphenol dicyanate ester


Samikannu Rakesh and Muthusamy Sarojadevi

A new keto-ene functionalized 1, 5-bis (4-hydroxyphenyl)penta-1,4-dien-3-one (HPDO) was prepared from p-hydroxy benzaldehyde and acetone using boric acid as a catalyst. The prepared bisphenol was converted into 1,5-bis (4-cyanatophenyl) penta-1,4-diene-3-one (CPDO) by reacting with cyanogen bromide (CNBr) in the presence of triethylamine. The synthesized bisphenol and the dicyanate ester were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H-NMR and 13C-NMR) and elemental analysis (EA) techniques. CPDO was then blended with a commercial bisphenol-A dicyanate ester (BADCy) at different ratios (100:0, 75:25, 50:50. 25:75, 0:100) and the cure characteristics were studied. CPDO was found to be cured at a lower temperature than BADCy. The cyanate ester blends were cured at 373 K (30 min) → 423 K (30 min) → 473 K (60 min) → 523 K (3h). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the thermal properties. DSC studies show that the cure (peak) temperature of CPDO with and without a catalyst was found to be 408 K and 466 K respectively. The initial degradation temperature of the cured resins was found to be in the range from 701 K to 705 K. The Limiting Oxygen Index (LOI) value, determined by Van Krevelen’s equation, shows that these blends have good flame retardant properties. 

[1] Fang T. and Shimp D.: Prog. Polym. Sci., 1995, 61. 
[2] Fan J., Hu X. and Yue C.: J. Polym. Sci, Part B. Polym. Phys., 2003, 41, 1123.
[3] Herr D., Nikolic N. and Schultz R.: High Perform. Polym., 2001, 13, 79.     
[4] Hamerton I. and Hay J.: Polym. Inter., 1998, 47, 465.  
[5] Hamerton I. and Hay J.: High Perform. Polym.,1998, 10,163.
[6] Shimp D. and Chin B.: Chem. & Techn. Cyanate Ester Resins, 1994, 230. 
[7] Nair C., Mathew D. and Ninan K.: Adv. Polym. Sci., 2001, 155, 1.
[8] Hamerton I.: Chemistry and technology of cyanate ester. Chapman & Hall, London 1994.
[9] Rath S., Boey F. and Abadie M.: Polym. Int., 2004, 53, 857.
[10] Bao J., Li Y. and Chen X.: Chinese J. Polym. Sci.,2001, 19, 53.
[11] Zainol I., Day R. and Heatley F.: J. Appl. Polym. Sci., 2003, 90, 2764. 
[12] Gu A., Liang G., Lan L. and Zheng X.: J. Northwestern Polytechn. Univ., 1996, 14, 163. 
[13] Glauser T. and Johansson M.: Polymer, 1999, 40, 5297.
[14] Gaku M.: Polym. Mater. Sci. Eng., 1994, 71, 621.
[15] Mathew D., Reghunadhan Nair C. and Ninan K.: Polym. Int., 2000, 49, 48.
[16] Reghunadhan Nair C., Mathew D. and Ninan K.: Adv. Polym. Sci., 2001, 155, 1.
[17] Van Krevelen D.: Polymer, 1975, 16, 615.
[18] Borden D.: J. Appl.Polym.Sci., 1978, 22, 239.