Depth-profiles of structure in single- and multilayered commercial polymer films using grazing-incidence X-ray diffraction

Abstract

Grazing-incidence X-ray diffraction is used to analyze the variation in structural features—such as crystalline index and crystallite size-perfection (CI and CSP)—with depth in several commercially relevant mono- and multi-layer polymer films. The CI and CSP at the casting-roll surface of a melt-cast and biaxially oriented nylon 6 (N6) film is the same as in the bulk, but the air-exposed surface has lower CI and CSP than the bulk. These differences are attributed to the influence of the initial crystallization behavior at the two surfaces (roll-surface poorly ordered than the air-surface) on the eventual crystallinities observed after drawing. In a bilayer laminate of poly(chlorotrifluoro ethylene) (PCTFE), and poly(ethylene–ethyl acrylate) (EEA), the CI is lower but the CSP of PCTFE appears to be higher at the interface between PCTFE and EEA. The technique was able to find differences in the PE unit cell volume within the PE layer at the air/PE and PE/N6 interface in a three-layer film (PE/N6/PE). The method was also used to monitor the variation in preferred orientation with depth in the aluminum layer deposited on polymer films in a multilayered structure, as well as to examine the thin surface coatings.