Biodegradable PLA/PBS multinanolayer membrane with enhanced barrier performances

Polyester multilayer membranes with more than 2000 alternating layers of poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) were successfully prepared via a nanolayer coextrusion process equipped with a multiplying-element device. This process allows to make films consisting of very thin layers of polymers and in which a confinement effect of the semicrystalline polymer can be induced at point to significantly improve its physical properties. In this work, a homogeneous multinanolayer film of PLA/PBS was obtained without defaults or delamination, while the two polymers are immiscible. Continuous and homogeneous ultrathin layers of PBS (~45 nm) were obtained and the resulting confined structure of PBS led to an improvement of its barrier performances until 30% for oxygen, 40% for water and 70% for carbon dioxide. This improvement was explained by a decrease of the solubility coefficient and surprisingly not by the diffusion coefficient. This result was attributed to a slight orientation of the crystals in the extrusion direction and to the probable presence of an interphase between the layers of PLA and PBS.