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Spectral analysis of the infrared radiation emitted from thin films of resin transferred from the surface of high performance aerospace carbon fibreepoxy composite prepregs and heated to the cure temperature allows the cure chemistry and kinetics to be monitored in real time. Quantitative spectra with excellent signal‐to‐noise ratio are obtained by heating a thin resin film on a platinum hotplate fitted to the external optics of a Fourier transform infrared (FTIR) spectrometer and referencing the resulting emission (with the platinum emission subtracted) to a graphite black body at the same temperature. The resulting spectra are identical to absorption spectra and the quantitative features of the analysis are demonstrated by the appearance of isosbestic points during the curing reactions, so indicating that concentration profiles of the reacting species may be obtained. From the initial rate of amine and epoxy consumption, activation energies of 75kJ mol−1 were obtained for both functional groups in the uncatalysed resin 4,4′‐tetraglycidyl diamino diphenyl methane (TGDDM) with 27% 4,4′‐diaminodiphenylsulfone (DDS), while values of 74 and 89kJ mol−1 were obtained for amine and epoxy consumption from the TGDDM/DDS prepreg catalysed with boron trifluoride monoethylamine (Hercules 3501–6), consistent with homopolymerization occurring in the prepreg as well as amine–epoxy addition. Analysis of the FTIR emission at 177°C of resin from prepreg aged up to 90h at 23°C and 55% relative humidity shows a lowering of epoxy and amine concentration and a higher rate of cure, consistent with the formation of catalytic species. This technique may be used to monitor changes in surface properties such as tack and resin transfer, in addition to changes in the cure profile of the aged epoxy propreg.

Abstraa:A model for the heterogeneous oxidation of polypropylene (PP) is proposed in which it is considered that there is a small initial fraction, po, of oxidizing centres which have a high local rate of oxidation. Within these zones there is a free radical chain reaction producing secondary oxidation products, volatiles and chemiluminescence (CL) from peroxy radical termination reactions.These zones progressively spread (rate coefficient b/s-') and the free radical reactions die away within the volume of the original zones, producing a measurable concentration of oxidation products (rate coefficient a h 1 ) . Analysis of the CL-time curve as representing the instantaneous infectious, fraction, pi, in the spreading model enables the parameters p,, b and OL to be determined and profiles of the remaining fraction @, ) and dead or oxidized fraction (pd) constructed. Analysis of CL curves from 1200C to 150°C gives an activation energy for spreading in PP particles of 96kTlmol. Both single particles and groups of particles of different types of PP have been examined and evidence is presented of rapid surface spreading of oxidation from particle to particle.One of the contradictions in the study of the oxidation of polyolefins has been the success in applying a homogeneous free radical kinetic description of oxidation (typical of liquid hydrocarbons) to a solid polymer which, while above its glass transition temperature, is still well below the melting point. The kinetic analysis is usually based on oxygen uptake data or product accumulation curves measured spectroscopically (e.g. by infrared carbonyl index), which show features of an autoaccelerating chain reaction with an induction period, an exponential increase to a steady oxidation rate, followed by a decrease in rate at high extents of oxidation (ref 1). Models of various levels of complexity have been used to extract rate coefficients which may then be used to predict oxidation rates at different temperatures (ref 2 ).Investigations of the structure and morphology of solid polyolefins during oxidation have revealed that this apparently 'homogeneous' macromolecular oxidation has resulted in 0

The versatility of FTIR spectrometry was explored by considering a variety of samples drawn from industrial applications, materials science and biomedical research. These samples included polymeric insulators, bauxite ore, clay, human hair and human skin. A range of sampling techniques suitable for these samples is discussed, in particular FTIR microscopy, FTIR emission spectroscopy, attenuated total reflectance and photoacoustic FTIR spectrometry. The power of modern data processing techniques, particularly multivariate analysis, to extract useful information from spectral data is also illustrated.