Properties of pyrolytic network products from bis(phthalonitrile) polymers

Network bis(phthalonitrile) polymers were prepared by thermal polymerization of 4, 4'-(4, 4'biphenylyienedioxy)diphthalonitrile (BPPN) or the mixture of BPPN and tetracyanobenzene (TCB) in the presence of amine coreactants. The pyrolysis of these polymers was performed in a nitrogen atmosphere at temperatures stepwise elevated at an interval of 50°C. The thermal degradation began at about 450°C and was accelerated with increase of temperature. In the pyrolysis between 600 and 650°C, remarkable increases in density and elastic modulus were accompanied with a simultaneous sharp drop in resistivity. From results of X-ray, Raman, FT-IR, and 13C CP-MAS NMR measurements, it was found that the two-dimensional partially carbonized structures containing a considerable amount of nitrogen were formed for the pyrolyzates pyrolyzed at 500-700°C. In the pyrolysis between 80 0 and 900°C, the planar cyclic structures formed at the temperature of 600'-650°C were partially broken into the three-dimensional networks of amorphous carbon with the progress of carbonization. The highly carbonized pyrolyzate of moulded sheets was found to have a density of I.65 g/cm3, an elastic modulus of 27 GPa, and a resistivity as low as 0.02 Ωcm.