Polyethylene Raman spectroscopy

Raman spectrum [INFRARED TECHNOLOGY AND RAMAN SPECTROSCOPY - RAMAN SPECTROSCOPY] (Voll4) Low density polyethylene pDPE)... 

In this review the definition of orientation and orientation functions or orientation averages will be considered in detail. This will be followed by a comprehensive account of the information which can be obtained by three spectroscopic techniques, infra-red and Raman spectroscopy and broad line nuclear magnetic resonance. The use of polarized fluorescence will not be discussed here, but is the subject of a contemporary review article by the author and J. H. Nobbs 1. The present review will be completed by consideration of the information which has been obtained on the development of molecular orientation in polyethylene terephthalate and poly(tetramethylene terephthalate) where there are also clearly defined changes in the conformation of the molecule. In this paper, particular attention will be given to the characterization of biaxially oriented films. Previous reviews of this subject have been given by the author and his colleagues, but have been concerned with discussion of results for uniaxially oriented systems only2,3). 

In this review recent theoretical developments which enable quantitative measures of molecular orientation in polymers to be obtained from infra-red and Raman spectroscopy and nuclear magnetic resonance have been discussed in some detail. Although this is clearly a subject of some complexity, it has been possible to show that the systematic application of these techniques to polyethylene terephthalate and polytetramethylene terephthalate can provide unique information of considerable value. This information can be used on the one hand to gain an understanding of the mechanisms of deformation, and on the other to provide a structural understanding of physical properties, especially mechanical properties. 

Another polymer symposia was organised by IUPAC in 1947 in Liege. At this conference, the discussion included synthesis and technology of polymers like polyethylene, nylon, polyester. New characterisation methods such as x-ray scattering, x-rays, electron microscope, osmometry, nmr, IR, Raman spectroscopy, etc. were now available for characterisation of polymers. These methods become essential because of increasing complexity of new polymers. 

R.R Paradkar, S.S. Sakhalkar, X. He and M.S. Ellison, Estimating crystallinity in high density polyethylene fibers using online Raman spectroscopy, J. Appl. Polym. Sci., 88, 545-549 (2003). 

S.S. Cherukupalli and A.A. Ogale, Online measurements of crystaUinity using Raman spectroscopy during blown film extrusion of a linear low-density polyethylene, Polym. Eng. Sci, 44, 1484—1490 (2004). 

Fourier transform NMR spectroscopy, polyethylene thermal oxidation, 695 Fourier transform-Raman spectroscopy hydroperoxides, 692 nitrile hydrolysis, 702 see also Raman spectroscopy Four-memhered peroxides, 164, 1212-13 FOX (Xylenol Orange-ferric complex) assay hydrogen peroxide determination, 628, 632, 657, 658... 

Tanaka, H. and Takemura, T. Studies on the high-pressure phases of polyethylene and polytetrafluoroethylene by Raman spectroscopy. Polymer J. 12, 355 (1980)... 

Paradkar, R.P. Sakhalkar, S.S. He, X. 8t Ellison, M.S. Estimating Crystallinity in High Density Polyethylene Fibers Using Online Raman Spectroscopy /. Appl. Polym. Sci. 2003, 88, 545-549. 

In this study, Raman spectroscopy and pattern-recognition techniques were used to develop a potential method to differentiate common household plastics by type [87-89], which is crucial to ensure the economic viability of recycling. The test data consisted of 188 Raman spectra of six common household plastics high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), and polyvinylchloride... 

The study of polymer surfaces would certainly greatly benefit from HREELS contributions, electron-induced vibrational spectroscopy being often presented as the surface counterpart of the classical optical infra-red and Raman spectroscopies. However, the first HREEL spectra from polymer surfaces were published only in 1985 for thin organic films (2), in 1986 for a real insulating thick polyethylene... 

Commercially available polyethylene fiber has a degree of crystallinity between 70 and 80% and a density 0.97 gcm . There is a linear relationship between density and crystallinity for polyethylene. A 100% crystalline polyethylene will have a theoretical density, based upon an orthorhombic unit cell, of about lgcm . A totally amorphous polyethylene (0% crystallinity) will have a density of about 0.85gcm . Khosravi et al. (1995) used nitric acid attack on gel-spun polyethylene fibers to observe structural imperfections such as fold, molecular kinks and uncrystallized regions. Raman spectroscopy has been used to study the deformation behavior of polyethylene fiber. This technique gives peaks for the crystalline and amorphous states of polyethylene (see Chapter 9). 

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