Principles and Utilization of the Electron Beam Damage of Synthetic Polymers
The rapid decomposition of polymeric samples is a major problem in structural investigations of these materials, as the crystallographic information and mass/thickness contrast can be quickly lost. The X-ray elemental analysis can also be affected by loss of elements and often extrapolation to zero exposure is necessary. It is thus of great interest to know how quickly this decomposition occurs for a given polymer.The beam damage rate can be measured by loss of crystallinity, loss of mass or loss of elements. The measured decay curves can be approximated by a double exponential function for which only three constants are needed. This describes the behaviour of most polymers very well, however an accurate experimental evaluation of these constants is not easy. The most important and difficult parameters to measure are the initial intensity, exposure and size of the irradiated area. It is not clear why the double exponential function is suitable, if it is a chemical law or if it fits purely by coincidence.