Physical properties and enzymatic hydrolysis of poly (L-lactide)-TiO2 composites

Amorphous poly(L-lactide) (PLLA) composite films with titanium dioxide (TiO2) particles were prepared by solution-casting using methylene chloride as a solvent, followed by quenching from the melt. The effects of surface treatment, volume fraction, size, and crystalline type of the TiO2 particles on the mechanical properties and enzymatic hydrolysis of the composite films were investigated. The tensile strength of the PLLA composite films containing TiO2 particles except for anatase-type ones with a mean particle size of 0.3-0.5 mum was lowered and the Young's modulus became higher with increasing the content of TiO2 particles. The tensile strength of the composite films containing anatase-type TiO2 with a mean particle size of 0.3-0.5 mum at contents of 20 wt % or less was almost the same as that of the pure PLLA film. The enzymatic hydrolysis of PLLA matrix was accelerated by the addition of the hydrophilic anatase-type TiO2 particles (nontreated or Al2O3 treated) with a mean particle size of 0.3-0.5 mum at relatively high contents such as 20 wt %. On the other hand, the enzymatic hydrolysis of PLLA matrix was inhibited by composite formation with the hydrophobic rutile-type TiO2 particles (Al2O3-stearic acid treated, or ZrO2-Al2O3-stearic acid treated). These results suggest that the mechanical properties and enzymatic hydrolyzability of the PLLA can be controlled by the kind and amount of the added TiO2 particles. (C) 2005 Wiley Periodicals, Inc.