Antioxidants abiotic degradation

A good deal is now known about the kinetics of abiotic peroxidation and stabilisation of carbon-chain polymers and it is possible in principle to extrapolate to the time for ultimate oxidation from laboratory experiments. As already indicated, the key determinant of the time to bioassimilation is the antioxidant and if this is chosen to optimize the service life, bioassimilation can also be achieved as in the case of wood, straw, twigs, etc. It seems that straw is a particularly appropriate model for the biodegradation of the polyolefins since, like the polyolefins, it fully bioassimilated in biologically active soil over a period of about ten years. The most important conclusion from recent work is that nature does not depend on just one degradation mechanism. Abiotically initiated peroxidation is just as important, at least initially as biooxidation. 

Nocardia [23] and P. aeruginosa were shown to break the cis-PI chain by an oxidative mechanism since aldehyde groups were found to accumulate during microbial degradation. This is always the first product formed during the abiotic peroxidation of cis-Fl and the evidence suggests that the bacteria initiate a radical-chain peroxidation, which is inhibited by antioxidants. This will be discussed further in the context of poyolefin biodegradation. 

It will be seen in Section 4 that the rate of the abiotic and hence the biodegradation process can be readily controlled by antioxidants whereas no comparable control process has yet been developed for hydro-biodegradable polymers. A second conclusion was that starch plays no part in the biodegradation of a polyethylene matrix until the latter has been extensively peroxidised in the presence of transition metal ions. Similar conclusions have been reached by Wool [56] who showed that in the absence of PE degradation in starch-PE blends, biodegradation is controlled by the rate of migration... 

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