Dye Diffusion in Polymer Films Subjected to Supercritical CO₂: Confocal Raman Microscopy and Modelling

Abstract

Summary: Poly(ethylene terephthalate) films impregnated with Disperse Red 1 from a supercritical CO2 solution were studied using confocal Raman microscopy. Depth profiles of films dyed for different periods of time were measured using the oil immersion approach and concentration‐depth plots of the relative dye concentration were generated. A one‐dimensional Fickian diffusion model was used to evaluate the diffusion coefficient of the dye from the Raman microscopy data using a non‐linear least squares regression. The calculated diffusion coefficient at 200 bar and 80 °C was 6.75 ± 1.01 × 10−14 m2 · s−1.Typical example of Raman spectra acquired during depth profiling.imageTypical example of Raman spectra acquired during depth profiling.

Raman and Infrared Imaging of Dynamic Polymer Systems

“…Upon removal from the loading conditions, each system exhibited measurable increases in the depth of penetration over time by either the dye or the chlorinated polyolefin, respectively. The uptake of dye by PET followed a Fickian diffusion profile and the estimated diffusion coefficient of the dye was consistent with literature values of similar species 66. The presence of solvent in the PP/EPR blend system appeared to induce dissolution of the EPR domains during the loading process 67.…”

“…Loading can be accomplished by swelling the substrate with a solvent mixture that contains the species to be loaded. Confocal Raman microscopy has been used to assess the loading of an azeo dye into the surface of a PET film66 and the loading chlorinated polyolefins into poly(propylene)–ethylene propylene rubber (PP/EPR) blends 67. Upon removal from the loading conditions, each system exhibited measurable increases in the depth of penetration over time by either the dye or the chlorinated polyolefin, respectively.…”

Supercritical fluid dyeing of synthetic and natural textiles – a review

“…The first phenomenon can be described by Fick's law of diffusion as PET is above its glass transition temperature when immersed in the plasticising supercritical solvent [101,102]. The diffusion coefficient of disperse dyes in PET films and fibres in the presence of scCO 2 ranges from 10 -11 to 10 -15 m 2 /s [86,91,[101][102][103][104], values which are from one to three orders of magnitude higher than the corresponding values determined during conventional aqueous dyeing of hydrophobic textiles [101,105]. This is connected to the swelling and plasticising action of scCO 2 that acts as a 'molecular lubricant' [106], enhancing the dye mobility in the amorphous regions of the polymer.…”

Sorption of C. I. Disperse Red 60 in polystyrene and PMMA films and polyester and Nylon 6 textiles in the presence of supercritical carbon dioxide

“…West et al [28] measured dye partitioning and diffusion coefficient in supercritical fluids using the in situ UV-VIS spectroscopy. Fleming et al [29] measured dye diffusion in PET films in supercritical CO 2 using confocal Raman microscopy. The corresponding diffusion coefficient at 20.0 MPa and 353.2 K was 6.75±1.01×10 −14 m 2 /s.…”