Toward Sustainable PLA-Based Multilayer Complexes with Improved Barrier Properties
Résumé
Poly(lactic acid) or PLA is currently considered as one of the most promising substitutes of conventional plastics, with low environmental impact, especially for food packaging applications. Nevertheless, some drawbacks, such as high permeability to oxygen, are still limiting its industrial applications. The objective of this study was to highly increase the oxygen barrier performance of PLA without compromising its sustainable nature and following the principles of circular economy perspective. Coproducts coming from mill industries, such as wheat gluten proteins (WG), were used to produce PLA-WG-PLA multilayer complexes with improved barrier performance. Different technologies of industrial interest were considered: high-pressure homogenization of WG film forming dispersions, corona treatment of industrial PLA films, wet casting and spin coating for tailoring the WG coating thickness, and hot-pressing for shaping the multilayers. The impact of all these strategies on the properties (surface and bulk) and performances (barrier and adhesion) were investigated on the single constituent layers as well as on the final laminate. The most efficient complex increased more than 20 times (or 2000%) the barrier properties to oxygen and ∼20% the barrier properties to water vapor, considering application conditions (50% relative humidity and 25 °C). The low thickness (∼60 μm) of this complex also matched the requirement for flexible packaging applications. High-pressure homogenization, WG coating thickness, and hot-pressing positively and highly impacted the final properties of the multilayer, while the contribution of corona treatment was limited. This study unambiguously evidenced the potential of PLA-WG-PLA complexes as a valid sustainable substitute for high performing conventional plastics, and it could open an unexplored PLA market opportunity. In addition, it could motivate further investigations on PLA-based laminates for industrial interest, using other biopolymers from agro-industrial waste or byproducts.
Mots clés
sustainable development
Spin coating
Poly(lactic acid) PLA
Surface modification
plastic material
Hot-pressing
High-pressure homogenization
Corona treatment
Biobased and biodegradable polymers
Wheat gluten
WATER-VAPOR BARRIER
POLY(LACTIC ACID)
GLASS-TRANSITION
ANTIMICROBIAL PROPERTIES
PROTEIN ISOLATE
POLYLACTIC ACID
CARBON-DIOXIDE
EFFICIENT GAS
FILMS
OXYGEN