Imaging chemiluminescence applied to oxidation of rubber materials and polyamide

Abstract: In this thesis the heterogeneous nature of thermal oxidationof polymer materials have been investigated by imagingchemiluminescence (KL). The issues of oxidation depth profilesand physical spreading of oxidation in rubbers materials andpolyamide have been addressed.For this purpose an ICL instrument was designed showing thefollowing unique features: high sensitivity - particularly highsignal to noise ratio for small samples, high spatialresolution and a high accuracy of the in-plane temperature.With these characteristics, the spatial distribution of the CLemission from various polymer materials can be obtained inoxygen and, which has not previously been reported, in nitrogenatmosphere.An experimental method was developed to estimate theoxidation depth in HTPB tubber duringin situoxidation. Thein situoxidation depth data were correlated to oxidation depthprofiles of pre-aged samples from measurements in nitrogenatmosphere. Oxidation depth profiles in nitrogen were alsodetermined for pre-aged PA 6,6 and correlated to carbonyl indexdepth profiles obtained by FlTR microscopy. By subjetting HTPBrubber samples to static as well as dynamit-mechanical load at100&degree;C different oxidation depth profiles could beidentified.Experiments on oxidation in populations of EPDM particlesdemonstrated the presence of two separate distributions ofinitiation times for the individual particles, suggesting twodifferent initiation mechanisms. Further experiments showed acorrelation of the initiation times of adjacent particles. Thecorrelation was improved in populations with closerinterparticle distances. The results were interpreted in termsof a physical spreading of the oxidation from particle toparticle. Results from GC-MS and TG measurements indicated thepresence of volatile species released on oxidation of theparticles.A mechanism is proposed for the physical spreading ofoxidation observed, involving infectious spreading in the gasphase from heterogeneously distributed initiation sites.Keywords:Imaging chemiluminescence, oxidation, depthprofiles, physical spreading, HTPB rubber, EPDM, PA 6,6.