Moisture Barrier of Polylactic Acid/Graphene Nanocomposite Films

Moisture barrier properties of nanocomposite films of polylactic acid (PLA) and graphene nanoplatelets (GNP) were studied. Polylactic acid is a bioderived and biodegradable polymer which can be a substitute for conventional polymers as a packaging material if its barrier properties can be improved. Graphene nanoplatelets were dispersed in the PLA matrix via melt-blending to act as moisture barriers. Moisture permeability was measured as a function of graphene concentration using MOCON® water vapor transmission equipment. It was found that at a loading of only 1.2 vol% GNP, the water vapor permeability was reduced by 35% compared to neat PLA. This result is better than that observed with PLA/clay nanocomposites under identical conditions. Graphene nanoplatelets are severely agglomerated, and TEM pictures show large areas through which diffusion can occur without any hindrance. An explanation is presented to account for the observed behavior.