Plasticization of poly(lactide) with blends of tributyl citrate and lowmolecular weight poly(D,L-lactide)-b-poly(ethylene glycol) copolymers

摘要

Polylactide (PLA) is a potential candidate for the partial replacement of petrochemical poly-mers because it is biodegradable and produced from annually renewable resources. Char-acterized by its high tensile strength, unfortunately the brittleness and rigidity limit itsapplicability. For a great number of applications such as packaging, fibers, films, etc., it isof high interest to formulate new PLA grades with improved flexibility and better impactproperties. In order to develop PLA-based biodegradable packaging, the physico-mechanical proper-ties of commercially available PLA should be modified using biodegradable plasticizers. Tothis end, PLA was melt-mixed with blends of tributyl citrate and more thermally stable lowmolecular weight block copolymers based on poly(D,L-lactide) and poly(ethylene glycol) ofdifferent molecular weights and topologies. The copolymers have been synthesized using apotassium based catalyst which is expected to be non toxic and were characterized byutilization of TGA, GPC and NMR techniques. The effect of the addition of up to 25 wt% plasticizer on the thermo-mechanical proper-ties of PLA was investigated and the results were correlated with particular attention to therelationship between properties and applications. To confirm the safety of the catalyst used for the preparation of the copolymers, in vitrocytotoxicity tests have been carried out using MTS assay and the results show their bio-compatibility in the presence of the fibroblast cells. Compost biodegradation experiments carried out using neat and plasticized PIA haveshown that the presence of plasticizers accelerates the degradation of the PLA matrix.