EVALUATION OF THE BIODEGRADABILITY OF COPOLYESTERS CONTAINING AROMATIC-COMPOUNDS BY INVESTIGATIONS OF MODEL OLIGOMERS

Model oligo esters of terephthalic acid with 1,2-ethanediol, 1,3-propa nediol, and 1,4-butanediol have been investigated with regard to their biodegradability in different biological environments. Well-character ized oligomers with weight-average molar masses of from 600 to 2600 g/ mol exhibit biodegradation in aqueous systems, soil. and compost at 60 degrees C. SEC investigations showed a fast biological degradation of the oligomer fraction consisting of 1 or 2 repeating units, independe nt of the diol component used for polycondensation, while polyester ol igomers with degrees of polymerization higher than 2 were stable again st microbial attack at room temperature in a time frame of 2 months. A t 60 degrees C in a compost environment chemical hydrolysis also degra des chains longer than two repeating units, resulting in enhanced degr adability of the oligomers. Metabolization of the monomers and the dim ers as well by the microorganisms could be confirmed by comparing SEC measurements and carbon balances in a ''Sturm test'' experiment. Based on these results degradation characteristics of potential oligomer in termediates resulting from a primary chain scission from copolyesters consisting of aromatic and aliphatic dicarbonic acids can be predicted depending on their composition. These results will have an evident in fluence on the evaluation of the biodegradability of commercially inte resting copolyesters and lead to new ways of tailor-made designing of new biodegradable materials as well.