Two-stage degradation

This two-stage degradation of methyl ketones to carboxylic acids containing one fewer carbon atoms cannot be realized in all cases, but only when the acetyl group is attached to a quaternary carbon as in pinacone and a series of aryl methyl ketones of the acetophenone type. 

From TGA traces (see Figure 3.4) it can be readily seen that the cnred resins are much less thermally stable than Teflon or polycarbonate (PC). There is also an indication of a two-stage degradation for the cured DER 331 resin. From DTA traces for cured and uncured resins, it is shown that the characteristic exothermic peak between 300-380 °C is at least partially caused by some reaction of the epoxy group. 

Figure 1. Schematic representation of a polymeric metal complex (left) and two stage degradation mechanism, at the metal center via macroligand dissociation (center) and along the polymer backbone (right).

Researches on thermal degradation of purified and well-defined (R)-hydroxyl-to-isopropyl ester PCL have proposed a two-stage degradation mechanism - Scheme 18( 1) displays the cis-elimination mechanism and Scheme 18(2) shows the nnzipping process 852663 a.l53. ... 

A commercial technology (69), the SABRE process, treats contaminated water and soil ia a two-stage process by adding a readily degradable carbon and an inoculum of anaerobic bacteria able to degrade the contaminant. An initial aerobic fermentation removes oxygen so that the subsequent reduction of the contaminant is not accompanied by oxidative polymerization. 

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