Characterization of Erucamide Profiles in Multilayer Linear Low-Density Polyethylene and Propylene-Ethylene Copolymer Films Using Synchrotron-Based FT-IR Microspectroscopy

The diffusion of erucamide in single layer polymer films has been monitored previously using FT-IR microspectroscopy [Appl. Spectrosc., 53, 11 (1999)]. This research extends that work to multilayer films. In particular, erucamide migration is characterized in press-laminated bilayer and coextruded trilayer linear low-density polyethylene (LLDPE) films and also coextruded bilayer films of LLDPE and a propylene-ethylene copolymer (PEC). Results in bilayers and trilayers demonstrate that the erucamide prefers to migrate to a film surface rather than into an adjacent layer, even in the presence of steep concentration gradients at layer–layer boundaries. The same behavior was observed for bilayers of LLDPE and PEC where it was anticipated that erucamide may diffuse into the less dense PEC layer. Attenuated total reflectance FT-IR was also used to confirm that little or no erucamide diffused through an additive-deficient layer to reach a film–air interface in a bilayer structure. However, results clearly showed erucamide migration from a core layer through additive-deficient skin layers to reach the surfaces of a trilayer film.