Technical Lignin Valorization in Biodegradable Polyester-Based Plastics (BPPs)

Abstract

Synthetic plastics have been reshaping the planet since the early 20th century. They have brought plenty of conveniences to our lives; meanwhile, plastic wastes discarded into the environment are resistant to biodegradation, accumulating in soil, water, and even in organisms. Biodegradable polyester-based plastics (BPPs), such as polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS), polycaprolactone (PCL), and poly(β-hydroxybutyric acid) (PHB) are considered to be ecofriendly and sustainable alternatives and have thrived rapidly in the past few decades. However, the applications of BPPs have been limited by their high prices compared to conventional plastics, while blending with lowcost fillers has been deemed to be a facile and efficient solution to the foregoing issues. Technical lignin, a class of biodegradable aromatic polymers, has been extracted/isolated at a large scale as a coproduct in the conventional paper-making and the emerging lignocellulosic biorefinery industries. The economically competitive BPP composites reinforced by coproduct lignin could not only facilitate the lignin valorization but also improve the economic viability of the lignocellulosic biorefinery. At present, the key obstacle lies in the incompatibility between lignin and BPPs resulting from self-aggregation and thermal condensation of lignin due to its polyhydroxy aromatic structures. Herein, we overviewed a series of effective approaches to promote the interaction between lignin and BPPs by adding plasticizers and blocking the hydroxyl groups. Furthermore, lignin can act as functional fillers endowing lignin/BPP composites favorable versatilities and expanding their applications in the fields of flame retardant packaging, food packaging, medical materials, outside packaging, and mulching films. In the end, we review the developments of lignin/BPP blending composites in the future and propose current problems that need to be solved.

Recent advances in lignin-based carbon fibers (LCFs): precursors, fabrications, properties, and applications

“…4, and a detailed description of these methods and subsequent applications has been reported previously. 40 In general, chemical modifications of lignin can be categorized into two types: (1) new chemical sites can be added to lignin, such as sulfonation, nitration, amination and hydro-xyalkylation; and (2) functionalization of hydroxyl groups, such as etherification, esterification, phenolization, and alkylation/ dealkylation, which can contribute to the interfacial compatibility between lignin and polymer. Additionally, graft, copolymerization, or propargylation are also used for tailoring linear structures of lignin.…”

“…4, and a detailed description of these methods and subsequent applications has been reported previously. 40…”

Electrochemical Depolymerization of Lignin in a Biomass‐based Solvent**

“…[1][2][3] In this context, lignocellulose biorefinery has been recognized as a potential candidate to replace petroleum refinery, while being a carbon-neutral and non-food feedstock. [4][5][6][7] Lignocellulosic biomass consists mainly of cellulose, lignin, hemicelluloses, and extractives. Comprising three different phenylpropane monomer units (monolignols), lignin is the second most abundant macromolecule on earth, while its annual production is estimated in the range of 100 million tons.…”

“…Therefore, the sustainable production of fuels and valuable chemicals based on the efficient use of renewable resources has become an urgent matter [1–3] . In this context, lignocellulose biorefinery has been recognized as a potential candidate to replace petroleum refinery, while being a carbon‐neutral and non‐food feedstock [4–7] . Lignocellulosic biomass consists mainly of cellulose, lignin, hemicelluloses, and extractives.…”

Synergistic Effect of Sodium Alginate and Lignin on the Properties of Biodegradable Poly(vinyl alcohol) Mulch Films

“…16 Therefore, biodegradable films have to be produced to solve "white pollution" while offering the same performance as traditional petroleum-based films. 17 Green biodegradable mulch films have been widely studied in recent years. The biodegradable material is one that can itself be completely broken down into carbon dioxide and water by microorganisms such as bacteria, fungi, and actinomycetes.…”