William T. K. Stevenson

The stability of polymers in low earth orbit

Abstract Most organic polymers and some on polymeric materials such as silver or pigments suffer appreciable surface damage in the form of erosion or oxidation when exposed to the low earth orbit (LEO) environment encountered on shuttle flights. Surfaces facing the direction of flight suffer the most damage because of ram effects. Typical thickness losses for plastic films (eg. epoxy, Kapton, Mylar) can be 5 – 10μm. The aggressive chemical nature of the LEO environment (including atomic oxygen and O + ions), aided by the high collision energies of the gases with forward facing surfaces, are thought to be responsible for the erosion and oxidation.

A spectroscopic study of the carbonisation of poly(acrylonitrile) and poly(acrylonitrile-co-acrylic acid)

Abstract The advantages and limitations of modern infra-red (ir) and solid state 13 C nuclear magnetic resonance (NMR) spectroscopic techniques are described for the characterisation of poly(acrylontrile) (PAN) and poly(acrylonitrile-co-acrylic acid) after various thermal treatments. The thermal treatments were chosen to model the pre-oxidation and carbonisation steps in the production of carbon fibres from PAN. Infra-red is particularly useful in following reactions of nitrile groups and the production of carbonyl species. Nuclear magnetic resonance spectroscopy is particularly valuable in following aromatisation processes. Both techniques are more limited by problems in spectral assignments than by difficulties in obtaining spectra. At high carbonisation temperatures (>500°C) 13 C NMR is restricted by the reduction in the amount of hydrogen available for the effective use of cross polarisation techniques.

Infrared spectroscopy of carbon-filled polymers

Application de la spectrometrie IR a reflexion interne a la caracterisation de caoutchoucs EPDM renforces de noir de carbone et de resines epoxyde charges de carbone