Fate of Aromatic Sequences and Risk Assessment

A major point of criticism for aliphatic-aromatic copolyesters is the final degradability of the aromatic sequences in the polymers. In such statistical copolyesters there are domains in the polymer chains, where several aromatic dicarboxylic acids are linked with the alcohol component, without being interrupted by an aliphatic dicarboxylic acid. The distribution of sequence lengths depends on the ratio of aliphatic and aromatic dicarboxylic acids, and can be calculated for an ideal random copolymerisation using (Equation 10.1)  

Warjnj fraction of the aromatic dicarboxylic acid (in mol%) located in sequences of the length n. 

As an example, the distribution of the sequence lengths for a BTA 45 55 copolyester (45% terephthalic acid in the acid component) are listed in Table 10.4. 

Length of aromatic sequence (number of repeating units) Fraction of terephthalic acid monomers in the sequences of length n (mol% of terephthalic acid monomers) 

Reproduced with permission from U. Witt, R-J. Muller and W-D. Deckwer, Journal of Environmental Polymer Degradation, 1996, 4, 1, 9. 1996, Springer 

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