Studied on mechanical, thermal and dielectric properties of BPh/PEN-OH copolymer

The thermosetting 4,4′-bis(3,4-dicyanophenoxy)biphenyl (BPh) was modified with the hydroxy-terminated poly(aryl ether nitrile) (PEN-OH). Two different crosslinking reactions including the polymerization of the nitrile groups and the formation of triazines were coexisted in the BPh/PEN-OH system, which depended on the different curing temperature. Moreover, along with the processing of crosslinking, the microstructure changed to plastic fracture first and then became brittle fracture (T > 320 °C), which was observed from SEM. The copolymer system showed good mechanical properties, outstanding thermal stability (over 520 °C) and high char yield (86.1% at 600 °C). Furthermore, they exhibited excellent dielectric properties. Both the dielectric constant and dielectric loss were found to be relatively stable over a wide range of frequencies ranging from 100 Hz to 200 kHz. Moreover, the dielectric stability was also found with respect to temperature.