BEAM DAMAGE OF POLYPROPYLENE IN THE ENVIRONMENTAL SCANNING ELECTRON-MICROSCOPE - AN FTIR STUDY

The environmental scanning electron microscope allows the examination of virtually any specimen in a gaseous environment without the need fo r coating or drying, Experimental evidence, however, suggests that sig nificant electron beam damage occurs in hydrated specimens. It is thou ght that water molecules, ionized by the electron beam, produce hydrog en and hydroxyl free radicals which attack the organic material of the sample. In order to elucidate the beam damage mechanisms, areas of po lypropylene films were exposed to the electron beam at varying doses a nd exposure times under both hydrating and dehydrating conditions. The chemical changes occurring as a result of electron-beam irradiation w ere determined using Fourier transform infra-red microscopy. Direct in teraction of the electron beam with the polymer results in extensive c ross-linking, In the presence of water, free-radical-initiated reactio ns lead to hydrolysis and oxidation of the polymer.