Photodegradation polymer morphology

Rabello, M.S. White, J.R. The role of physical structure and morphology on the photodegradation behaviour of polypropylene. Polym. Degrad. Stab. 1997, 56, 55-73. 

Figure 18.21a, b illustrates the extent to which the judicious stabilization is able to protect PO resins and their blends from the thermo- or photodegradation. As they indicate, the recyclates even after five extrusions show performance within 10 % approximating that of a virgin material. Similar behavior is expected for strongly immiscible polymer blends, under the condition that the recyclates will be re-compatibilized to recover the original morphology. 

The strueture of poly(ethylene-co-carbon oxide) (1.4 wt% CO) was studied by 50.3 MHz carbon-13 NMR spectroscopy [296]. With model compounds, assigments of new structures and previously undetected products of photodegradation and photo-oxidation in the solid state were made. Four per cent of the CO groups were aecounted for as ethyl ketones with the remainder being randomly distributed along the polymer backbone ehain. Evidence was presented for the formation of cis, trans-cyclobutanols. A novel a-branched ketonic structure was also found. The reactivity of ketonic groups is affected by polymer matrix morphology. 

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