Synergistic effect of silver nanoparticle content on the optical and thermo-mechanical properties of poly(L-lactic acid)/glycerol triacetate blends

Monodispersed silver nanoparticles (Ag-NPs) were synthesized by chemical reduction in aqueous medium and transferred in chloroform to be redispersed in the plasticized matrix of poly(l-lactic acid) (PLA) by melt compounding. PLA nanocomposites were prepared using a combination of Ag-NPs in amounts of 0.01, 0.025, 0.05, 0.075 and 0.1% in weight, with 10 pph (parts per hundred) of glycerol triacetate (GTA) to be characterized by UV-Vis and Fourier transformed infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Optical properties showed that PLA nanocomposites have monodispersed Ag-NPs due to the intense SPR (surface plasmon resonance) absorption band at 414 nm, with a calculated particle size of similar to 30 nm. The crystallinity is gradually raised at a maximum level (21.1%) compared to the pure PLA (2.3%) and T (g) drastically decreased from 61 to 36.8 A degrees C when Ag-NPs are incorporated in the plasticized PLA matrix. These results were consistent with the enhanced elastic modulus in DMA analysis, explained from the viewpoint of a good nanofiller dispersion and crystallization behavior, providing a stable and ordered crystal (alpha-form) in agreement with FTIR and DSC analysis. Finally, the outcomes indicate a synergistic effect between Ag-NPs and the plasticizer GTA, due to the nucleating effect of the monodispersed Ag-NPs and the mobility chain promoted by the plasticizer in the macromolecular arrangement of the PLA.