Study of Pyrolytic Conversion of Polycarbodiimide to Glass-like Carbon Film

Abstract

We have developed a new starting polymer for glass-like carbon film; poly-carbodiimide (PCDI). The purposes of this paper are to determine the structure of the carbonized PCDI and to reveal the mechanism for the carbonization.After heat treatment at 1000°C, the total yield was ca. 75 % and the density reached 1.78g/cm3. These values are much higher than the ordinary starting resins, such asphenolic resin, cellulose and PVC. The carbonized PCDI also has higher mechanical strength and gas permeability. These properties can be explained by the high density of the crystalline and the inter-crystalline structures.The IR spectrum shows that two kinds of crosslinkage, dimer and trimer, are formed densely below 230°C in air. These crosslinkages come from reactive carbodiimide groupsin the molecular main chain of PCDI. Partial oxidation of the sample promote the formation of the trimer from the dimer and the carbodiimide groups, so that the sample becomes more heat stable.