Preparation of Modified-TiO_2/PLA Nanocomposite Films: Micromorphology, Photo-degradability and Antibacterial Studies

摘要

Today bio-nanocomposites of biopolymers are from great interest from the point of view of environmentally friendly concerns (1). Among all types of PLA nanocomposites, the ones including oxides of semi-conductive materials such as TiO_2 have attracted the attention of many research centers and industries due to their photocatalytic and antibacterial properties (2). Although there seems to be a great interest about producting the nanocomposite of PLA and TiO_2 nanoparticles, but aggregation of TiO_2 nanoparticles in an organic matrix like PLA, makes it difficult to reach a homogenous film with good properties (3). Therefore, using a method in order to modify TiO_2 nanoparticles surface before introducing into the PLA matrix, seems to be necessary. In this study first, PLA chains were grafted onto TiO_2 nanoparticles surface via reactive melt mixing using a novel approach in presence of SnCl_2 as catalyst. In this step, PLA grafted chains were characterized on the TiO_2 nanoparticles using FTIR analysis. Then, PLA-grafted-TiO_2/PLA nanocomposite films with different amounts of modified TiO_2 nanoparticles, were produced using a twin screw extruder. The micro structure of nanocomposite films was characterized using SEM technique, and this way, it was observed that the dispersion state of TiO_2 nanoparticles has been greatly improved after modifying TiO_2 surface. Finally, the PLA-grafted-TiO_2/PLA nanocomposite films were put under UV irradiation, in the range of 360-420 nm, for 2 months and the weight loss of the films was followed during this period. The nanocomposite films containing modified TiO_2 nanoparticles, showed higher amount of weight loss in comparison with the film containing bare TiO_2 nanoparticles. The PLA-grafted-TiO_2/PLA nanocomposite films were also used to investigate the antibacterial properties against both gram negative and gram positive bacteria, under UV irradiation for 2 hours, using a combined method of JIS Z2801:2000 and ASTME2180-07. The