Correlation between polypropylene microstructure, cold plasma interaction and subsequent luminescent emission

Preliminary results on the effect of polymer structure on the plasma-induced luminescence of polypropylene are reported. The spectral features of the light emission following plasma treatment at liquid nitrogen temperature have been analysed on commercial and laboratory-made polypropylene films of different structure. We observed that, for the less crystalline sample, the magnitude of the chemiluminescent component, which peaks at 400nm, was initially lower than for the others, but that it was less sensitive to the accumulation and the duration of the treatments. This feature has been explained by the formation of more isolated carbonyl groups in the case of this sample, which would result from a deeper penetration of active species created by the plasma discharge, or a larger fraction of amorphous regions associated with a larger proportion of oxygen in the bulk. A parallel effect was seen in the luminescent component ascribed to charge recombination on conjugated chromophores, with wavelength emission in the range 500–600nm. © 1998 SCI.