Detection of elastic strain in an amorphous polymer by X-ray scattering

Abstract

For crystalline solids, the displacement of diffraction peaks with applied elastic strain is the basis of one method of measuring internal stress^1,2. The effect has been exploited for both metals³ and crystalline polymers⁴. Hitherto, the diffuse character of diffraction peaks obtained from non-crystalline materials has discouraged similar measurements on them. Working with atactic polymethyl methacrylate (a-PMMA) as an example of non-crystalline polymer glasses (which can sustain elastic strains up to several per cent before plastic yield or fracture), a displacement of the most intense diffraction peak has been observed in response to applied elastic strain. This peak corresponds to intermolecular correlations in the polymer^5,6.