Abstract
Multifunctional bioplastics have been prepared by amorphous reassembly of cellulose, hemicelluloses (xylan), and hydrolyzed lignin. For this, the biopolymers were dissolved in a trifluoroacetic acid–trifluoroacetic anhydride mixture and blended in different percentages, simulating those found in natural woods. Free-standing and flexible films were obtained after the complete evaporation of the solvents. By varying xylan and hydrolyzed lignin contents, the physical properties were easily tuned. In particular, higher proportions of hydrolyzed lignin improved hydrodynamics, oxygen barrier, grease resistance, antioxidant, and antibacterial properties, whereas a higher xylan content was related to more ductile mechanical behavior, comparable to synthetic and bio-based polymers commonly used for packaging applications. In addition, these bioplastics showed high biodegradation rates in seawater. Such new polymeric materials are presented as alternatives to common man-made petroleum-based plastics used for food packaging.
Highlights
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants
It is a natural composite material made of robust cellulose fibers that are embedded in a matrix of both hemicelluloses and lignin
One of the most common subgroups of hemicelluloses are xylans whose chemical structure is made up of β1,4-linked xylopyranosyl residues with side branches of αarabinofuranose and α-glucuronic acids
Summary
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. The main components of wood are cellulose, hemicelluloses, lignin, and different extractives such as aliphatic/alicyclic compounds (terpenes, fatty acids, and alcohols), phenolic compounds, sugars, and alkaloids.[1] Cellulose is the most abundant renewable polymer on earth, with a total annual biomass production of 1.5 × 1012 tons It is composed of very long linear polymer chains of D-glucopyranosyl linked by β-1,4-. Depending on the type of plant biomass, xylan can have different side groups and can be chemically modified by acetylation It contributes to the cross-linking of cellulose microfibrils and lignin through ferulic acid residues, in grasses, and through lignin-carbohydrate complexes in higher woody plants.[3−5] Xylans are commercially used in different activities, including bread and livestock industries and as a natural food sweetener and second-generation fuel, to mention a few.[6] Lignin is the second most abundant natural polymer after cellulose, with an annual production of ∼500 million tons.[7] It is considered as the polymer matrix that provides rigidity, compressive strength, and protection against water from the external environment to the cell wall. It is used in different applications, for instance, as a filler in composite plastic materials, cosmetics, and fire retardants and as feedstock for biofuel production.[8]
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