Polyethylene Raman imaging

FIGURE 9.15 Raman spectra of the plastics (a) high-density polyethylene (HDPE), (b) low-density polyethylene (LDPE), (c) polyethylene terephthalate (PET), (d) polypropylene (PP), (e) polystyrene (PS), and (f) polyvinylchloride (PVC). (From Pattern Recognition, Chemometrics, and Imaging for Optical Environmental Monitoring, Siddiqui, K. and Eastwood, D., Eds., Proceedings of SPIE, 1999, pp. 103-112. With permission.)... 

The characterization of polymers often reqnires the separation of the other components, including otganic components. It is based on the nse of density gradients or organic solvents. Quantification nsing imaging is adapted for large objects, but there is a problem in the case of microparticles. In this case, the use of infrared spectroscopy (in transmission or reflection mode) which compares the spectra of samples to the spectra of a reference is the most appropriate method to characterize polypropylenes, polyethylenes and polyesters. Raman spectroscopy is sometimes used, as well as calorimetry, for the characterization of the fumes after combustion. 

Y.J. Lee, C.R. Snyder, A.M. Forster, M.T. Cicerone, W.-L. Wu, Imaging the molecular structure of polyethylene blends with broadband coherent Raman microscopy. ACS Macro Lett. 1, 1347-1351 (2012)... 

The use of a fibre-coupled confocal Raman microscope and an infrared microscope for both point mapping and global imaging in the study of spatial variations in polymer chemistry and morphology is illustrated by studies of the curing of the UV-cured acrylate coatings, crystallinity in drawn polyethylene terephthalate (PET) film, molecular orientation in PET bottles, and the analysis of a PES/PEES copolymer blended with epoxy resin and cured at elevated temperature. 8 refs. 

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