A Kinetic Analysis of the Thermo-Oxidative Degradation of PU/POSS nanohybrid Elastomers

Abstract

A series of polyurethane/polyhedral oligomeric silsesquioxane (PU/POSS) nanohybrid elastomers, synthesized from diphenylmethane-4,4’-diisocyanate (MDI), po- lyoxytetramethylenediol (PTMG), 1,4-butanediol (BD) and 1-(1-(2,3-dihydroxypropoxy)butyl)-3,5,7,9,11,15-isobutyl- pentacyclo-[9.5.1.13,9.15,15.17,13]-octasiloxane(PHIPOSS), have been submitted to thermal stability investigations under an oxidizing atmosphere. The polymers were prepared with differing amounts of silsesquioxane units in their hard segments (0, 4 and 10 wt. %). It was observed that POSS influenced the thermal stability of PU/POSS nanohybrid systems both in the first and second stage of the degradation process. Ozawa–Flynn–Wall and Friedman Kinetic analyses revealed that the activation energy (Ea) and pre-exponential factor (A) increased in the first stage and decreased in the second stage of the thermal degradation as a result of PHIPOSS introduction into PU elastomers. The best approximation of the f(α) function was found for the reaction of nth order with autocatalysis/n-dimensional nucleation model in case of neat PU and reaction of nth order with autocatalysis/reaction nth order model for the nanohybrid elastomers