EVOLUTION OF CRYSTALLINITY IN PHOTODEGRADED POLYETHYLENE FILMS STUDIED BY FT-RAMAN SPECTROSCOPY

FT-Raman spectroscopic studies of photodegraded polyethylene films have enabled the evolution of the crystallinity process to be measured. Commercial polyethylene films of M(W)=90000 were exposed in a weathering UV-chamber under known conditions of exposure time and radiant energy. The spectral profiles were modelled using Fourier methods. The relative amounts of the orthorrombic crystalline phase, alpha(c) the amorphous phase, cia and the interphase, alpha(b), were calculated using Raman bands at 1416 cm(-1) characteristic of the crystalline phase and the bands at 1080, 1305 cm(-1), characteristic of the amorphous phase. The interphase content can be calculated from the relationship alpha(b)= 1-(alpha(c)+alpha(a)). It was found that the weathering process affects only the relative intensities of the bands attributed to crystalline and amorphous fractions; the crystalline content increases at the expenses of the amorphous fraction. These results are discussed in terms of the changes in the intermolecular forces caused by radiation exposure.