Thermal properties of ZnO and bimetallic Ag-Cu alloy reinforced poly(lactic acid) nanocomposite films

Poly(lactic acid) (PLA)-based nanocomposite films were prepared by incorporating zinc oxide (ZnO) (< 50 and < 100 nm) and bimetallic Ag-Cu alloy (< 100 nm) nanoparticles (NP), and polyethylene glycol as a plasticizer via a solvent casting method. Thermal properties of the nanocomposites films were investigated using differential scanning calorimeter and thermogravimetric analyzer. The addition of 20 % PEG to the neat-PLA decreased the glass transition temperature (T (g)) significantly from about 60 to 17 A degrees C, whereas the melting temperature (T (m)) did not drop significantly. Metallic nanoparticles increased the T (g); however, Ag-Cu alloy exhibited a greater increase than ZnO nanocomposite films. Particle size of ZnO NP did not show significant difference in the T (g) values of the films. The T (m) value of the nanocomposite films was not influenced by the NP. The addition of plasticizer initiated the crystallization (cold and melt) of the PLA/PEG blend, which was substantially improved by the incorporation of NP in the composite films, in particular, 1 mass% loading. Non-isothermal crystallization was significantly affected by the cooling and heating rates. Thermogravimetric analysis data indicated that only Ag-Cu alloy could improve the thermal stability of nanocomposite films. Furthermore, nanoparticles significantly influenced the UV barrier and the transmittance of plasticized films.