SUPERCRITCAL FLUID POLYMER PROCESSING: A CONFOCAL RAMAN MICROSCOPIC INVESTIGATION

Abstract: This study evaluates the dyeing of polymers under high-pressure and supercritical (sc) CO2 conditions using confocal Raman microscopy. The effects of the dyeing conditions are evaluated in terms of morphological alterations to the host polymer matrix and the distribution of the impregnated dye as a function of depth. The impregnation of polymers with doping solutes is performed in a ‘solvent-free ’ manner with the use of scCO2. The application of scCO2 technology in polymer processing is an attractive alternative to conventional methods largely due to the ease of removal of CO2 following processing. Of particular promise is the use scCO2 to replace water in the industrial dyeing of textile fibres. The polymeric materials employed in the textile industry are generally polyesters and specifically poly(ethylene terephthalate) is widely used. Much information is needed regarding the effects of the processing conditions on polymer morphology and the dye distribution. Confocal Raman microscopy promises to be a premier tool to investigate the processed polymers and thus a tool to guide process optimisation. Confocal Raman microscopy enables a material to be z-sectioned, whereby Raman spectra are acquired as a function of depth in a non-destructive manner. The Raman spectra of PET processe