Polyethylene fibres Spectra

Table 2. Laser-Raman spectrum of oriented polyethylene fibres...

Figure8.6 Raman spectrum in the region 1080-1 lS0cm for an experimental high-m ulus gel-spun polyethylene fibre (after [S9]). The Raman band has been fitted to two Gaussian curves, (a) Fibre undeformed (b) at a strain of 4.06%...

Polyethylene. The Raman spectrum of polyethylene has been known for some years and all the bands have been identified seemingly unambiguously. Recently the spectrum has been recorded using stretched large-diameter fibres as a sample. The spectra were recorded with the fibre bundled vertically, horizontally and end-on in a Cary 81 spectrometer. The arrangements are illustrated in Fig. 3. The electric vector of the helium-neon laser is set vertically and therefore in the first orientation (a), the fibre axis and electric vector are parallel. 

Using this approach, dichroism is found in the spectra which enable one to distinguish modes where the vectors are parallel or perpendicular to the fibre axes. The type of dichroism typical in these experiments is illustrated in Fig. 4. If one accepts the principle that the Raman band will be maximized in intensity when the electric vector of the source and the movement vectors of the atoms in the normal mode are parallel, it is possible to assign the Raman spectrum of polyethylene to fundamental... 

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