Polymeric Schiff Bases. VII. Some Parameters in the Evaluation of the Thermal Stability of Poly(p-Xylylidene-p-phenylenediamine)

Thermogravimetric analyses of poly(p-xylylidene-p-phenylenediamine) in nitrogen, helium, and air yield stability values substantially identical to values obtained from tests in vacuo. The respective thermal stability values in nitrogen and in air are unchanged over a fourfold change in gas flow rates. Slightly lower values are found at heating rates of 5–15°C/min than at 30°C/min. Thermal stabilities are lower in oxygen than in air, but the values are still relatively high. Higher apparent thermal stability values are observed when a powder sample of 10 mg is evaluated as a single mass rather than as a fine powder. Calorimetric measurements indicate that Schiff base polymers which have been heated in nitrogen to 1000–1200°C have not been converted to graphite-type polymers. The Schiff base polymers are resistant to radiation; their stability is shown to be independent of dose rate and of the nature of the ionizing radiation.