Characterization of Erucamide Profiles in LLDPE Films: Depth-Profiling Attempts Using FTIR Photoacoustic Spectroscopy and Raman Microspectroscopy

Abstract

This research focuses on mapping the concentration profile of erucamide in LLDPE film. Attenuated Total Reflectance (ATR) FTIR and FTIR microspectroscopy (FTIR-mS) have both been used previously to map concentration profiles in polymer films. However, ATR-FTIR spectroscopy is restricted to the near-surface region of a film while FTIR-mS works well in the film bulk but has deficiencies near film surfaces. Two other techniques, Raman microspectroscopy (R-mS) and FTIR photoacoustic spectroscopy (FTIR-PAS), reportedly work well for depth-profiling in polymers with micron or submicron resolution. Experiments were conducted with R-mS and FTIR-PAS to attempt to quantify the spatial distribution of erucamide in LLDPE film. The amide I carbonyl peak was identified from neat erucamide powder for both R-mS and FTIR-PAS. That peak was not observed with R-mS for film containing erucamide, even for films with a relatively high erucamide loading (1 wt.%). However, FTIR-PAS could detect statistically significant differences in erucamide concentration as a function of penetration depth, indicating that FTIR-PAS may be used as an effective depth-profiling tool for the erucamide-LLDPE system.