Scanning force microscopy of bulk-filled uniaxially oriented poly(ethylene terephthalate) films

Bulk-filled uniaxially oriented poly(ethylene terephthalate) film surfaces have been investigated by scanning force microscopy. Comparison with additive-free films shows that the addition of filler particles during manufacture increases the final surface roughness of the films. Filler particles at or near the surface are accompanied by deep depressions aligned in the direction of draw. Raised plate-like features oriented diagonally to the draw direction are present on all the films. Lateral Force Microscopy shows that this overlayer region is of lower friction and phase imaging shows that it is of higher phase shift than the surrounding polymer. The observations imply that the raised material is more crystalline than the surrounding background.