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Application of diffuse reflectance spectrophotometry (DRS) in the investigation of stable and semi-stable products of radiolysis in solid state radiation chemistry creates the possibility of spectrophotometric measurements in the case of opaque objects of investigation, e.g. virgin polypropylene in powder. The main advantages of the method are: (1) the object of investigation may be used in any physical shape (hardly transpartent films, opaque powders); (2) The measurement is non destructive; (3) No solvents which could influence transients and final products of radiolysis are necessary; (4) Only optical spectra (200–1000 nm) of intermediate species and final products created during irradiation are observed, since unirradiated sample is used as the reference; (5) the method is complementary to EPR, because it shows spectra of not paramagnetic species, which do not give EPR signals. Numerous spectra of irradiated polypropylene have been recorded, some of them have been identified as due to peroxides. Other remain to be identified or are waiting to be subject of working hypotheses. The new approach is in the phase of beginnings, and collected material is not equivalent in volume to the information gained by other methods. Discussion draws attention to the fact of variety of transient and final products of polypropylene radiolysis, caused by complicated nature of the irradiation object and heterogeneity of ionizing energy dissipation in the shape of ca 30% of energy deposited in multi-ionization spurs. |
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