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US-12624502-B2 - Lignocellulosic bioplastics and composites, and methods for forming and use thereof

US12624502B2US 12624502 B2US12624502 B2US 12624502B2US-12624502-B2

Abstract

A solid lignocellulosic bioplastic can be formed from a biomass comprising an intertwined structure of lignin, hemi-cellulose, and cellulose. The lignin in the biomass can be dissolved such that the cellulose is fibrillated. After the lignin dissolution and cellulose fibrillation, the lignin can be regenerated in situ. The regenerated lignin can be deposited on and can form hydrogen bonds between the fibrillated cellulose, so as to form a slurry of lignin-cellulose solids in solution. The slurry can then be dried to form the bioplastic. In some embodiments, the lignin is dissolved by immersing the biomass in a first chemical. The lignin can then be regenerated in situ by addition of a second chemical to the first chemical.

Inventors

  • Liangbing Hu
  • Chaoji CHEN
  • Qinqin XIA

Assignees

  • UNIVERSITY OF MARYLAND, COLLEGE PARK

Dates

Publication Date
20260512
Application Date
20210916

Claims (18)

  1. 1 . A method comprising: (a) subjecting a biomass to a first chemical treatment by immersing the biomass in a first solution comprising a deep eutectic solvent that comprises choline chloride and oxalic acid, the biomass comprising an intertwined structure of lignin, hemicellulose, and cellulose, the intertwined structure being comprised of microbundles having a cross-sectional diameter of at least 50 μm, the first chemical treatment being effective to dissolve the lignin in the biomass and to fibrillate the cellulose into microfibrils, nanofibrils, or both microfibrils and nanofibrils; (b) after (a), adding one or more second chemicals to the first solution and then mechanically agitating for a predetermined time such that at least some of the dissolved lignin is in situ regenerated, the regenerated lignin being deposited on the cellulose microfibrils and/or nanofibrils and forming hydrogen bonds between adjacent ones of the cellulose microfibrils and/or nanofibrils; (c) after (b), removing the deep eutectic solvent from the first solution while retaining the regenerated lignin and cellulose microfibrils and/or nanofibrils in the first solution so as to form a slurry of lignin-cellulose solids in solution; and (d) after (c), drying the slurry to form a solid lignocellulosic bioplastic from the lignin-cellulose solids, the bioplastic comprising an interconnected network formed by the cellulose microfibrils and/or nanofibrils bound together by the regenerated lignin.
  2. 2 . The method of claim 1 , further comprising: after (c) and prior to (d), depositing the slurry in a mold or cast, wherein the mold or cast defines a shape of the lignocellulosic bioplastic after (d).
  3. 3 . The method of claim 1 , further comprising: after (c) and prior to (d), depositing the slurry using a printhead or additive manufacturing nozzle, wherein locations of the depositing define a shape of the lignocellulosic bioplastic after (d).
  4. 4 . The method of claim 1 , wherein the biomass comprises wood, bamboo, grass, hemp, or reed.
  5. 5 . The method of claim 1 , wherein, after (a): the lignin in the slurry has β-O-4 ether bonds cleaved as compared to native lignin in the biomass prior to (a); hydroxyl groups of the lignin are more phenolic than before (a); and a —COO functional group of the cellulose has a negative charge.
  6. 6 . The method of claim 1 , wherein: after (a), each of the microfibrils and/or nanofibrils has a cross-sectional dimension less than or equal to 300 nm.
  7. 7 . The method of claim 1 , wherein: at least 90% of lignin in the biomass prior to (a) is retained in the slurry after (c); and less than or equal to 10% of hemicellulose in the biomass prior to (a) is retained in the slurry after (c).
  8. 8 . The method of claim 1 , wherein: (c) the drying of (d) comprises pressing the slurry while removing the one or more second chemicals therefrom.
  9. 9 . The method of claim 1 , further comprising: prior to (d), adding a polymer or a precursor thereof to the first solution, wherein, after (d), the solid bioplastic is a hybrid structure formed by a combination of lignin-cellulose solids and the polymer.
  10. 10 . The method of claim 9 , wherein the polymer comprises a natural resin or rosin, polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), polycarbonate (PC), polyethylene glycol (PEO), polyamide (PA), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyacrylonitrile (PAN), polycaprolactam (Nylon 6), poly(m-phenylene isophthalamide) (PMIA), poly(p-phenylene terephthalamide) (PPTA), polyurethane (PU), polypropylene (PP), high-density polyethylene (HDPE), polystyrene (PS), polycaprolactone (PCL), polybutylene succinate (PBS), polyglycolide (PGA), acrylonitrile butadiene styrene (ABS), polymethylsilane (PMS), or any combination of the foregoing.
  11. 11 . The method of claim 1 , wherein after (c) and prior to (d), a content of lignin-cellulose solids in the slurry is in a range of 5 wt % to 20 wt %, inclusive.
  12. 12 . The method of claim 1 , wherein the one or more second chemicals comprises water.
  13. 13 . The method of claim 1 , wherein the removing of (c) comprises filtering to separate the deep eutectic solvent and at least some of the one or more second chemicals from the first solution.
  14. 14 . The method of claim 13 , further comprising: (e) after (c), separating the deep eutectic solvent from the one or more second chemicals, wherein: the separated deep eutectic solvent is reused to dissolve lignin in another biomass; the separated second chemicals are reused in another first solution for in situ regeneration of lignin; and the separating of (e) comprises filtration, distillation, or both.
  15. 15 . The method of claim 1 , further comprising: after (d), pressing the solid lignocellulosic bioplastic to form a densified bioplastic.
  16. 16 . The method of claim 1 , wherein: the one or more second chemicals comprises water; during the first chemical treatment of (a), the first solution is maintained at a first temperature of at least 90° C. for a first time; and the predetermined time for the mechanically agitating in (b) is 0.5-4 hours, inclusive.
  17. 17 . The method of claim 16 , wherein the first temperature is about 110° C.
  18. 18 . The method of claim 1 , wherein: the first chemical treatment of (a) is also effective to dissolve the hemicellulose in the biomass; and after (b), at least part of the hemicellulose remains dissolved in the first solution.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application claims the benefit of U.S. Provisional Application No. 63/079,287, filed Sep. 16, 2020, entitled “Bio-based Composite Materials and Methods of Making the Same,” which is incorporated by reference herein in its entirety. FIELD The present disclosure relates generally to biomass-derived materials, and more particularly, to lignocellulosic bioplastics and composites, and methods of forming and using such materials. BACKGROUND Bioplastics are plastic materials at least partially formed from renewable biomass sources (e.g., plant or animal material). When made from different biomass feedstocks, bioplastics can reduce the reliance on fossil fuels and diminish greenhouse gas emissions. While some bioplastics may be biodegradable, other bioplastics may not be biodegradable or biodegrade at a rate similar to fossil-fuel derived plastics. Conventional bioplastics can be synthesized using delignification, chemical crosslinking, or modification of natural fibers. However, these approaches can employ toxic chemicals and involve complex processing steps associated with high manufacturing costs. Moreover, conventional bioplastics may have sub-optimal mechanical strength and stability upon exposure to water, for example, due to weak interfacial bonding and the hydrophilicity of cellulose and/or hemicellulose therein. Embodiments of the disclosed subject matter may address one or more of the above-noted problems and disadvantages, among other things. SUMMARY Embodiments of the disclosed subject matter system provide an in situ lignin regeneration strategy to synthesize a high-performance bioplastic from lignocellulosic biomass. In this process, the native structure of the biomass can be deconstructed to form a homogeneous cellulose-lignin slurry that features nanoscale entanglement and hydrogen bonding between the regenerated lignin and cellulose micro/nanofibrils. The resulting lignocellulosic bioplastic exhibits high mechanical strength, excellent water stability, UV-light resistance, and improved thermal stability. Furthermore, the lignocellulosic bioplastic has a lower environmental impact as it can be easily recycled or safely biodegraded in the natural environment. In one or more embodiments, a method comprises dissolving lignin in a biomass. The biomass can comprise an intertwined structure of lignin, hemicellulose, and cellulose. As a result of the lignin dissolution, the cellulose in the biomass can be fibrillated. The method can further comprise, after the lignin dissolution, in situ regenerating the lignin such that the regenerated lignin is deposited on and forms hydrogen bonds between the fibrillated cellulose. As a result, a slurry of lignin-cellulose solids in solution can be formed. The method can also comprise, after the lignin regeneration, drying the slurry to form a solid lignocellulosic bioplastic. In one or more embodiments, a bioplastic can comprise fibrillated cellulose and regenerated lignin. The fibrillated cellulose can be in a form of microfibrils or nanofibrils having a cross-sectional dimension less than or equal to 300 nm. The regenerated lignin can be deposited on and can form hydrogen bonds between the fibrillated cellulose so as to form an interconnected network. The regenerated lignin and the fibrillated cellulose can be derived from a same biomass that had an intertwined structure of native lignin, hemicellulose, and cellulose. The regenerated lignin can be chemically modified as compared to the native lignin in the biomass. Any of the various innovations of this disclosure can be used in combination or separately. This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The foregoing and other objects, features, and advantages of the disclosed technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments will hereinafter be described with reference to the accompanying drawings, which have not necessarily been drawn to scale. Where applicable, some elements may be simplified or otherwise not illustrated in order to assist in the illustration and description of underlying features. Throughout the figures, like reference numerals denote like elements. FIG. 1 is a simplified schematic diagram illustrating various aspects of forming a lignocellulosic bioplastic, according to one or more embodiments of the disclosed subject matter. FIG. 2A is a simplified cross-sectional view of an exemplary bioplastic structure, according to one or more embodiments of the disclosed subject matter. FIG. 2B is a simplified cross-sectional view of another exempl