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A. Niekraszewicz

Degradable copolymers of ethylene terephthalate

Polimery 1993, No 8-9, 399

DOI: dx.doi.org/10.14314/polimery.1993.399


The possibility of modifying polyethylene tercphthalatc) (PET) with L-lactic acid or with oligo(oxyethylene)diols with the aim of enhancing the hydrolytic degradability of PET was presented. By such modification biodegradable, cheap and environmentally safe polymeric materials arc to be prepared, suitable for conventional applications as well as for special purposes (in medicine, pharmacy, agriculture etc.). Copolyesters were prepared by ester— ester exchange between PET and poly(L-lactic acid) or by polycondensation reaction of PET and lactide. Depending on the conditions of synthesis and on substrates used, ethylene terephthalate/L-lactic acid copolyesters were prepared containing 5—40 mass-% of L-lactic acid residues. Some selected copolyesterethers containing 30—50 mass-% of oligoether sequences and copolycsters containing 10—40 mass-% of L-lactic acid residues were investigated in respect for their hydrolytic degradability in buffer solutions of appropriate pH values at 60°C. The hydrolytic stability was evaluated indirectly on the basis of weight loss and changes in appearance of samples after various periods of keeping them in a buffer solution as well as from the reduction in relative viscosity of polymer solution. A relationship between the content of oligoether blocks or L-lactic acid residues in the respective copolymers and their hydrolytic degradability was observed.

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