Green Additives in Chitosan‐Based Bioplastic Films: Physical, Mechanical, and Chemical Properties

Abstract

To switch to alternatives for fossil‐fuel‐based polymer materials, renewable raw materials from green resources should be utilized. Chitosan is such a material that is a strong, but workable derivative from chitin, obtained from crustaceans. However, various applications ask for specific plastic properties, such as certain flexibility, hardness and transparency. With different additives, also obtainable from green resources, chitosan‐based composites in the form of self‐supporting films, ranging from very hard and brittle to soft and flexible were successfully produced. The additives turn out to belong to one of three categories, namely linear, non‐linear, or crosslinking additives. The non‐linear additives could only be taken up to a certain relative amount, whereas the uptake of linear additives was not limited within the range of our experiments. Additives with multiple functional groups tend to crosslink chitosan even at room temperature in an acidic medium. Finally, it was shown that dissolving the chitosan in acetic acid and subsequently drying the matrix as a film results in reacetylation compared to the starting chitosan source, resulting in a harder material. With these findings, it is possible to tune the properties of chitosan‐based polymer materials, making a big step towards application of this renewable polymer within consumer goods.

Green Additives in Chitosan‐based Bioplastic Films: Long‐term Stability Assessment and Aging Effects

“…[1][2][3] Those might be currently readily available and likewise cheap, but their availability is rapidly declining and, even worse, they are one of the main emitters of global greenhouse gases. [4][5][6][7] Therefore, research aims at the discovery of green biomass-based alternatives for currently used materials by utilizing waste material that would otherwise be burned, landfilled, or end up in the sea. [1,[6][7][8][9] One such biopolymer that gains increasing attention because of its non-toxic, biodegradable properties is chitosan; the main derivative of the second most abundant polysaccharide chitin.…”

“…[4][5][6][7] Therefore, research aims at the discovery of green biomass-based alternatives for currently used materials by utilizing waste material that would otherwise be burned, landfilled, or end up in the sea. [1,[6][7][8][9] One such biopolymer that gains increasing attention because of its non-toxic, biodegradable properties is chitosan; the main derivative of the second most abundant polysaccharide chitin. [10] The polymer as such is mainly derived from byproducts from the fishing industry, about 10 12 to 10 14 tons of chitin are annually produced from living organisms in the ocean (e. g., shrimps, lobsters, and crabs) alone, making it widely available.…”

“…[6,7,10,[14][15][16] When cast as a film, chitosan shows inheriting properties well-suited as protecting materials, such as low permeability towards the air, as well as binding properties towards itself and certain substrates. [6] Nevertheless, to make chitosan-based materials competitive to established synthetic polymers, we need to be able to tune the material properties in a wide range, from stretchable to rigid, and from soft to hard, which we established in our previous work. [6] Additionally, the lifetime of the material is of equal or even greater importance.…”

“…[6] Nevertheless, to make chitosan-based materials competitive to established synthetic polymers, we need to be able to tune the material properties in a wide range, from stretchable to rigid, and from soft to hard, which we established in our previous work. [6] Additionally, the lifetime of the material is of equal or even greater importance. [17] As chitosan is intrinsically biodegradable, the long-term stability of fossil-based materials is hard to achieve.…”

“…[21] In general, though, abiotic degradation of plastic polymers precedes biodegradation and is initiated thermally, hydrolytically, or by UV light in the environment. [22] In this work, the stability of chitosan-based bioplastic alternatives, reported in recent work, [6] is investigated for 400 days, making use of different analytical methods (Figure 1). The dissolved chitosan is mixed with different kinds of additives, namely glycerol (GLY; red), [23][24][25] sorbitol (SOR; green), [24][25][26] polyethylene glycol (PEG; dark blue), [27][28][29] lactic acid (LAC; light blue), [24] citric acid (CA; yellow), [24,30] Tween 20 (T20; orange), [24,31] and Tween 80 (T80; violet) [32] and cast into large films.…”