ISSN:
0003-3146
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Comparative investigations of the polymeric residues remained after degrading polystyrene by heat or by UV irradiation reveal numerous profound changes of the structural and molecular parameters of the polymer when subjecting it to either of these main types of degradation.The polymeric residues of the commercial and of the prepared polystyrene samples were investigated in view of the following characteristics: discolouration, IR, UV and 13C NMR spectra, DSC-analysis, GPC-elution curves and X-ray patterns.The results show pronounced heterogeneity of the degradative reactions occuring in the framework of the thermal and photochemical degradation of polystyrene, including the existence of crosslinking processes and producing thus very inhomogeneous polymeric material.The presumption of the existence of different mechanism paths occuring in various polystyrene structural fractions was confirmed and further promoted, especially from the standpoint that the lower-molecular fractions of the polymer should behave more sensitively against the degradative attacks.Many-sided meanings of the informations obtained by analysing degraded polystyrene samples allow to postulate the present degradative mechanism by comparing among them various types of de gradative processes.The gained informations about the locations and ranges of absorption bands in UV, IR and 13C NMR spectra, as well as the complementary evidence from other determinations enabled the claim that polystyrene thermo-oxidative degradation would preferentially take place in the way to produce acetophenone structures near the chain ends. In the initial degradation periods this would be related with substantial lowering of the molecular mass.The photo-oxidative degradation mechanisms cause the build-up ketone and aldehyde structures and ring-opening reactions concurrent with chain crosslinking reactions.Comparing long-wave and short-wave UV irradiations of polystyrene does not only show the existence of inequal induction times, but additionally the presence of two sets of similar reactions leading to the production of many oxidized structures.The investigations would show that oxidative polystyrene degradation is a very complex phenomenon in which the prefered courses of chemical reactions are in the relations to the initial reaction steps, namely they do depend on structures formed in the early stages of the thermal and photo-degradative processes.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/apmc.1985.051370116
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