Environmentally friendly approaches for tailoring interfacial adhesion and mechanical performance of biocomposites based on poly(lactic acid)/rice straw

In the present research, plant-based biocomposites containing poly(lactic acid) (PLA) and rice straw (RS) as an annually renewable agricultural waste were studied. To enhance the properties of these filled systems, two environmentally friendly pulping methods were applied to remove the non-cellulosic components of RS and fibrillate the fibers. In addition, two reactive compatibilizers based on functional epoxy and maleic anhydride groups were incorporated into the biocomposites, using a reactive extrusion process. By pulping the RS fibers and modifying the PLA/lignocellulosic filler interface, the plant-based biocomposites with enhanced performance were attained. Furthermore, the elastic modulus, tensile strength, tensile toughness, impact strength, hardness, density and Vicat softening point of PLA and filled PLA system with untreated RS were improved. The impact resistance, tensile strength and elastic modulus of neat PLA were enhanced by 40 %, 160 % and 100 % for the modified biocomposites containing the environmentally friendly RS pulps. The obtained results showed that, these biocomposites had even higher mechanical performance than the PLA biocomposites containing RS pulp obtained through common soda-pulping method. The reasons behind these improvements are the partial pulping of RS, as well as the chain extension of PLA macromolecules and PLA grafting onto the lignocellulosic fiber surfaces induced by the reactive compatibilizers.

New Functional Bionanocomposites by Combining Hybrid Host-Guest Systems with a Fully Biobased Poly(lactic acid)/Poly(butylene succinate-co-adipate) (PLA/PBSA) Binary Blend

In this study, we have developed innovative polymer nanocomposites by integrating magnesium-aluminum layered double hydroxide (LDH)-based nanocarriers modified with functional molecules into a fully biobased poly(lactic acid)/poly(butylene succinate-co-adipate) (PLA/PBSA) matrix. These LDH-based hybrid host-guest systems contain bioactive compounds like rosmarinic acid, ferulic acid, and glycyrrhetinic acid, known for their antioxidant, antimicrobial, and anti-inflammatory properties. The bioactive molecules can be gradually released from the nanocarriers over time, allowing for sustained and controlled delivery in various applications, such as active packaging or cosmetics. The morphological analysis of the polymer composites, prepared using a discontinuous mechanical mixer, revealed the presence of macroaggregates and nano-lamellae at the polymer interface. This resulted in an enhanced water vapor permeability compared to the original blend. Furthermore, the migration kinetics of active molecules from the thin films confirmed a controlled release mechanism based on their immobilization within the lamellar system. Scaling-up experiments evaluated the materials' morphology and mechanical and thermal properties. Remarkably, stretching deformation and a higher shear rate during the mixing process enhanced the dispersion and distribution of the nanocarriers, as confirmed by the favorable mechanical properties of the materials.