CURING BEHAVIOR AND HIGH TEMPERATURE PROPERTIES OF PHTHALONITRILE COPOLYMERS

摘要

Phthalonitrile blends composed of 4,4′-bis(3,4-dicyanophenoxy)biphenyl (biphenyl PN) andrnoligomeric n=4 phthalonitrile (n=4 PN), biphenyl PN and diglycidyl ether of bisphenol A epoxyrn(epoxy), and n=4 PN and epoxy have been prepared and thermally cured with an aromaticrndiamine curing additive. The miscibility of the 50:50 blend compositions was investigated byrndifferential scanning calorimetry. A single glass transition temperature (T_g) was observed forrneach blend which suggests miscibility in the amorphous phase. The dynamic mechanicalrnproperties and the thermal stability of the cured biphenyl PN/epoxy and the biphenyl PN=4 PNrncopolymers were evaluated with varying biphenyl PN content. The measurements showed thatrnfor the cured biphenyl PN/epoxy copolymers the T_g and the thermal stability were increased withrna higher biphenyl PN concentration and with a higher cure temperature. Stepwise isothermalrnaging of the biphenyl PN/epoxy and the biphenyl PN=4 PN copolymers determined that bothrnhad excellent thermo-oxidative stability when heated to a maximum temperature of 343 ℃.