Probing the Concentration Profiles of Additives in Polymers by IR Microspectroscopy: The Diffusion of Cyasorb UV531 in Polypropylene

Abstract

The recent advancement in FT-IR microspectrometry has provided a convenient way to probe the concentration profiles of additives in polymers. This technique opens up intriguing prospects for investigating additive/polymer or polymer/polymer interaction. In this work, the diffusion of a UV stabilizer, UV531, in polypropylene was selected to illustrate the applications of an IR microscope to monitor the concentration profiles of additives in polymers. In addition, a nonlinear least-squares fitting program was written to obtain diffusion coefficients from concentration profiles based on a theoretical model of the diffusion process. Because IR spectroscopy is functional-group specific, this technique is relatively insensitive to the presence of impurities or other additives in studying additive diffusion in polymers. The sensitivity, the aperturing capability, and the high spatial resolution of FT-IR microprobes make it possible to characterize a wider range of diffusion experiments in a shorter period of time than can be done using traditional techniques.

Using Synchrotron-Based FT-IR Microspectroscopy to Study Erucamide Migration in 50-μm-thick Bilayer Linear Low-Density Polyethylene and Polyolefin Plastomer Films

“…Hsu et al reported on the use of FT-IR microspectroscopy (FT-IR/ mS) to map the concentration pro le of a UV stabilizer in 520-mm-thick polypropylene plaques. 16 In their experiments, they placed powdered stabilizer in contact with a neat plaque, allowed the stabilizer to diffuse into the plaque for a prescribed period of time, and then calculated the additive diffusivity based on the measured concentration pro le. In contrast to those mass-sorption (or ''diffusion in'') experiments, we wanted to track the proles of additive diffusing out of the polymer, which mimics the behavior in comm ercial lm.…”

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

“…A technique that has been used successfully to map concentration profiles in thicker films is known as FTIR microspectroscopy (FTIR-mS). In this method, a specimen is microtomed, mounted in a microcompression cell, and placed on a microscope stage such that one sees an endview of the film [4][5][6][7]. The microscope's aperture system and objective are then used to focus the infrared beam on the specimen.…”

Evaluating Bulk-to-Surface Partitioning of Erucamide in LLDPE Films Using FT-IR Microspectroscopy

“…However, the focus of our research is on the use of FT-IR m icrospectroscopy (FT-IR-m S) 7±9 to map the concentration pro® le of an erucamide slip agent in linear low-density polyethylene (LLDPE). Hsu et al 10 reported the use of this technique to m easure the extent to which a UV stabilizer penetrated into initially additive-free plaques of polypropylene (so-called``diffusion in' ' studies). From their results, Hsu et al were able to calculate diffusion coef® cients.…”