The effect of citrate ester plasticizers on the thermal and mechanical properties of poly(DL -lactide)

Citrate esters triethyl citrate, tributyl citrate, and acetyl tributyl citrate were used as plasticizers for amorphous poly(D,L-lactide) (PDLLA). The resultant compositions were analyzed by means of differential scanning calorimetry (DSC), dynamic mechanical thermal analysis, and tensile testing to investigate the properties of the blends. Glass transition temperatures (T _gs) obtained by DSC were also compared to theoretically calculated T _gs. Increasing plasticizer content decreased the resultant T _g of the blend with plasticizer efficiency enhanced as the molecular weight of the citrate ester increased. However, in blends with high plasticizer content, a lack of miscibility also occurred with increased molecular weight. Theoretical results were comparable with those obtained experimentally at compositions, which were miscible. Increasing plasticizer content increased the ductility and decreased the strength of the polymer. The addition of 10 wt % plasticizer to PDLLA decreased tensile strength by over 50% with the deterioration larger at higher concentrations of plasticizer.