Thermal properties and crystallization behavior of poly(ether ether ketone ketone)/poly(ether biphenyl ether ketone ketone) copolymers

Thermal properties of poly(ether ether ketone ketone) (PEEKK)/poly(ether biphenyl ether ketone ketone) (PEDEKK) copolymers were investigated by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The glass transition temperature (T_g) increases from 154°C to 183°C as the content of PEDEKK units increases. The melting point (T_m) of the copolymers varied in the range between 314°C and 409°C and showed the behavior of eutectic type copolymer. From the investigation of the crystallization behavior of the copolymers, it was found that the cold-crystallization temperature (T_c′) of the amorphous copolymers assumes a maximum value for the copolymer with a mole fraction of the PEDEKK segment (n_B) of about 0.6, isothermally crystallized PEEKK and the PEEKK/PEDEKK copolymer exhibit double-melting behavior.