PREDICTION OF LIFETIME OF POLY(2-HEXYNE) FILMS THROUGH THE KINETICS OF THERMOOXIDATIVE DEGRADATION FROM THERMOGRAVIMETRIC AND MOLECULAR-WEIGHT DATA

Substituted polyacetylenes suffer from important degradation in contac t with air at moderately high temperatures, making them useless since some mechanical properties are lost. To predict the lifetime a kinetic study of the thermooxidative degradation process for poly(2-hexyne) i s presented. Thermogravimetry and GPC have been used to analyse some v ariables representative of polymer degradation, namely weight loss due to emission of volatiles, oxygen uptake and molecular weight evolutio n. The weight of the samples presented an initial increase (due to oxi dation) followed by a quasi-linear decrease (due to volatilization). A mechanism considering both phenomena has been proposed and modelled, resulting in a kinetic equation which satisfies the whole degradation process. The evolution of weight loss has also been related to the cha in scission, obtaining a linear dependence in agreement with the propo sed degradation kinetic model. However, accurate quantification of oxy gen uptake presented some problems so that this variable can only be c onsidered as a qualitative indication of the degradation level.