Localised thermal analysis of a packaging film

A scanning probe microscope fitted with a fine platinum wire active heating element was used to examine the topography of a 300 mu m thick cross-secti on of a seven-layer polyolefin laminate designed for a food packaging appli cation. Localised thermomechanical analysis was carried out by positioning the probe over selected regions and heating the wire whilst detecting the c hange in cantilever deflection using the microscope stage. Different grades of polyethylene and a poly(ethylene-vinyl alcohol) barrier layer could be identified by softening behaviour at a resolution of 10 mu m or better - ev en in cases where there were no obvious changes in image contrast. (C) 1999 Elsevier Science B.V. All rights reserved.