Aromatic polyamides. V. Substituent effect on thermal properties

摘要

AbstractSome wholly aromatic polyamides derived from unsubstituted and chloro‐ and nitro‐substituted diamines have been studied from the viewpoint of their thermal stability, thermo‐oxidative stability, and thermal transitions. General relationships between thermal stability of a polymer and its chemical structure are described. Decrease in thermal stability of poly(1,3‐phenyleneisophthalamide) and poly(1,4‐phenyleneterephthalamide) due to substituents has been explained and supported in part by infrared spectral data. The effect of electron‐withdrawing substituents such as chloro and nitro in increasing the thermo‐oxidative resistance of the polyamides is pointed out. The thermal transitions (TgandTm) of these polymers are also reported. All the polyamides exhibit a broad exothermic peak in the 630–700°C temperature range, which probably corresponds to reactions (crosslinking and cyclization) responsible for the high char yield