CHROMATOGRAPHIC FINGERPRINTING AS A MEANS TO PREDICT DEGRADATION MECHANISMS

The degradation products of polymers are identifiable by chromatograph y. The degradation product patterns (or ''fingerprints'') formed depen d on the type of polymer, the degradation mechanism(s), and also the t ype of additive present in the material. The chromatographic fingerpri nt of biotically aged degradable low-density polyethylene (i.e., LDPE + starch + prooxidant) shows, in particular, the absence of low molecu lar weight carboxylic acids, which suggests an assimilation of these c arboxylic acids by the microorganisms. The degradation products of nat ural polymers are usually intermediates that are used again in the ana bolic cycles. It is possible to transfer the terminology from the natu ral polymers, where the catabolism of natural polymers consists of thr ee stages, and apply this also to the degradable synthetic polymers, D uring stage I the natural polymers degrade to their major building blo cks (e.g., amino acids, glycerol, hexoses, pentoses, etc.), during sta ge II these products are collected and converted to a smaller number o f even simpler molecules [e.g., acetyl-coenzyme A (CoA)]. In stage III , finally, the acetyl-CoA enters the citric acid cycle, where energy i s gained in parallel with the release of CO, and H2O.