Molecular and macromolecular structure changes in polyamide 11 during thermal oxidation - Kinetic modeling

Abstract

The oxidation kinetics of unstabilized polyamide 11 thin film under oxygen pressures up to 2.0 MPa was studied by means of ferrous ion method for hydroperoxides titration, size exclusion chromatography (SEC) for molar weight measurements and in situ FTIR monitoring for carbonyl build up. Oxidation was shown not to be limited by oxygen diffusion which militates in favor of the use of a simple kinetic model for simulating experimental data. The kinetic parameters of this model were estimated from literature for initiation and propagation, and from selective experiments such as aging under several oxygen pressures for the estimation of the termination rate constants, or exposures under inert atmosphere to investigate the solid state polymerization effects and tentatively check the boundary conditions of the model. The kinetic model simulates satisfyingly the overall experimental results using the minimal number of adjustable parameters (except for some reactions difficult to be experimentally isolated and studied).