Thermo-oxidative Degradation of Polyesterimides, Polyamidoimides, Aliphatic-Aromatic Polyamides

5 Thermo-oxidative Degradation of Polyesterimides, Polyamidoimides, Aliphatic-Aromatic Polyamides [7, 21, 40-43] 

Structure of polyphthalamides PPA-1 and PPA-2 represents alternation of aliphatic and aromatic sequences. 

TPA amide is formed by thermo-oxidation in melt and at low-temperature solid-phase oxidation. Light yellow crystals of TPA amide and TPA mixture occur and accumulate on the surface of mould samples during accelerated heat ageing at temperatures of 150-200 °C. TPA is a typical product of hydrolysis by macrochain ends. From our point of view, TPA amide product is of greater interest. Recall that analogous products (relative to polymer structure) were already observed in investigation of thermo-oxidative transformations of other APH. For example, pyromellite diimide, was identified in thermooxidation of PAI [7, 21] and classical polyimide Capton , and 2,2 -(l,4-phenylene)-bis-(phenylpyrazine), is formed by poly(phenylquinoxaline) ageing [7]. 

From our point of view, a specific feature of thermo-oxidation of aromatic and aliphatic-aromatic heterochain polymers is displayed in TPA amide formed during PPA thermooxidation. Unfortunately, this feature is insufficiently discussed in the literature yet. Three hypotheses were put forward in discussion of PDI formation at PAI thermo-oxidation  

Sequential burning of (oxidation) of aliphatic fragments from both sides of the imide cycle. 

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