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

Abstract

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.