All-Natural Sustainable Packaging Materials Inspired by Plant Cuticles

New sustainable composite materials inspired by plant cuticles have been fabricated by impregnation of fibrous cellulose substrates with a naturally occurring polyhydroxylated fatty acid (9,10,16-trihydroxypalmitic or aleuritic acid) and subsequent polymerization of the latter into polyaleuritate. A two-step preparation method is used, comprising of spraying and hot-pressing. The hot-pressing temperature is critical for the extent of polymerization of polyaleuritate and its alteration allows fine tuning of the mechanical properties, opacity, wettability, and water adsorption of the developed composite materials. The cellulose substrate controls other characteristics such as water permeability and thermal conductivity. Addition of carnauba wax into the polyaleuritate matrix results in improvement of water and oxygen barrier properties. Best results in terms of mechanical resistivity, transparency, water resistance, and low values of oxygen permeability are obtained for samples fabricated using hot-pressing temperature of 200 degrees C and with a final formulation of 80.6% of cellulose, 17.7% of aleuritic acid, and 1.7% of carnauba wax. Comparison of the composite properties with common plastics confirms that these plant cuticle-like materials can become promising alternatives to petroleum-based macromolecules for packaging applications.