Biodegradable poly(lactic acid)-based hybrid coating materials for food packaging films with gas barrier properties

The inclusion of biodegradable poly(lactic acid) (PLA) as an organic component into the inorganic silica networks was attempted to prepare environmentally friendly hybrid coating materials with improved gas barrier properties by using sol–gel method. The PLA film obtained by melt extrusion casting process was used as a substrate for coating with prepared PLA/SiO2 hybrids. Interfacial attraction between the organic and the inorganic phases in the hybrid was promoted by employing 3-isocyanatopropyltriethoxysilane (IPTES) as a silane coupling agent. Phase interaction, morphologies, crystallization behavior, and optical transparencies for the prepared hybrids were investigated not only to evaluate the phase compatibility, but also to present an evidence for the gas permeation behavior through the hybrid coated PLA film. The incorporation of the silica component at appropriate level of content substantially increased the resistance to gas permeation. The films retained high transparency, with optical transmittance of over 92%, and showed oxygen and water vapor barrier properties improved by 69.7% and 45.7%, respectively, over those of neat PLA film. Aging process improved the barrier properties of the hybrid coatings due to created dense network structures.