Poly(L-lactide)/ZnO nanocomposites as efficient UV-shielding coatings for packaging applications

Poly(L-lactide) (PLLA)/ZnO nanocomposites have been developed as efficient UV-shielding coatings for packaging applications. ZnO have been selected as the most suitable UV-shielding material over 10 different metallic nanoparticles. Results reveal a nucleating effect of ZnO in which PLLA crystallization half time is reduced from 7.4 to 4.7 min with only 0.05 wt % ZnO. UV-vis spectroscopy confirms the UV-shielding effect in PLLA/ZnO nanocomposites, where the ultraviolet spectrum is blocked by 61.2% for a concentration as low as 0.45 vol %, while the 95.9% of the visible radiation passes through the material. A schematic representation explaining obtained UV-shielding effect is constructed based on the photon mean free path reduction as ZnO concentration increases. Water contact angle increased from 81 degrees up to 91 degrees for the 5 wt % nanocomposite, which would result beneficial in view to develop materials for packaging applications. Dynamic mechanical analysis exhibits a T-g increase with nanoparticle loading arising from the chain confinement caused by the presence of ZnO interacting surfaces. (C) 2015 Wiley Periodicals, Inc.