Patent Application
20240083067
The present disclosure relates generally to processing of fibrous plant materials, and more particularly, to waste-free (or at least waste-reduced) processing for modifying native lignin in fibrous plant materials and products resulting therefrom.
Fibrous plant materials hold the potential to replace a broad range of non-renewable and/or petroleum-based products toward a sustainable society. Recent progress on processing natural wood into high performance, low cost and sustainable structural materials opens up a promising route to replace existing structural materials (e.g., steel and other alloys) that are widely used in construction, automotive and aerospace industries. For example, densified wood prepared by partially removing lignin and hemicellulose from natural wood followed by densification exhibits a strength of 580 MPa. Nanocellulose films have also been fabricated with a strength up to 1 GPa by removing 90% of lignin, while keeping the high degree of polymerization of cellulose. However, in conventional lignin-removal techniques, the delignification process consumes a relatively large quantity of chemicals and produces a relatively large quantity of liquid waste, causing additional operating cost, energy consumption, and environmental concerns. Embodiments of the disclosed subject matter may address one or more of the above-noted problems and disadvantages, among other things.
Embodiments of the disclosed subject matter provide lignin-modified fibrous plant materials and substantially waste-free processing for lignin modification of fibrous plant materials. In some embodiments, a natural fibrous plant material (e.g., wood, bamboo, etc.) can be infiltrated or infused with one or more chemicals, for example, via native channels of the natural plant microstructure (e.g., lumina formed by cellulose-based walls of longitudinal cells of the fibrous plant material). The chemical-infiltrated plant material can then be heated to yield a softened plant material, which retains the cellulose-based microstructure of the natural plant material as well as most or substantially all lignin that was present in the starting material. In some embodiments, the retained lignin can be modified, for example, having shortened macromolecular chains as compared to native lignin.
In some embodiments, the process can produce no or minimal liquid waste (e.g., black liquor). Rather, depolymerized fragments of lignin and/or hemicellulose can be immobilized within the microstructure of the softened plant material. In some embodiments, most or substantially all of the chemicals used to produce the modification can be reacted with lignin and hemicellulose during the heating, for example, to generate a softened plant material with a neutral pH. In some embodiments, the softened plant material can be subject to densification (e.g., via pressing) and/or drying to yield a structural material with desired mechanical properties (e.g., increased strength, increased flexibility, anisotropic elasticity, etc.). In some embodiments, any fluid produced by the processing (e.g., fluid squeezed out during densification and/or evaporated fluid or vapor escaping during drying) can be substantially-free of any chemicals used to produce the modification and/or salts resulting therefrom.
In one or more embodiments, a method can comprise infiltrating a piece of natural fibrous plant material with one or more chemical solutions. The method can further comprise after the infiltrating, subjecting the piece of natural fibrous plant material with the one or more chemical solutions therein to a first temperature of at least 80° C. for a first time so as to produce a softened piece of fibrous plant material. A content of modified lignin in the softened piece can be at least 90% of a content of native lignin in the piece of natural fibrous plant material. The modified lignin retained in the softened piece can have shorter macromolecular chains than that of the native lignin in the fibrous plant material.
In one or more embodiments, a structure can comprise a densified piece of fibrous plant material. The densified piece of fibrous plant material can have a density of at least 1.0 g/cm3 and modified lignin therein. The modified lignin can have shorter macromolecular chains than that of native lignin in natural fibrous plant material.
In one or more embodiments, a structure can comprise a dried piece of fibrous plant material. The dried piece of fibrous plant material can have modified lignin therein and can retain open lumina of a native microstructure of natural fibrous plant material. The modified lignin can have shorter macromolecular chains than that of native lignin in the natural fibrous plant material.
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.
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.
For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods and systems should not be construed as being limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present, or problems be solved. The technologies from any embodiment or example can be combined with the technologies described in any one or more of the other embodiments or examples. In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are exemplary only and should not be taken as limiting the scope of the disclosed technology.
Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. Additionally, the description sometimes uses terms like “provide” or “achieve” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms may vary depending on the particular implementation and are readily discernible by one skilled in the art.
The disclosure of numerical ranges should be understood as referring to each discrete point within the range, inclusive of endpoints, unless otherwise noted. Unless otherwise indicated, all numbers expressing quantities of components, molecular weights, percentages, temperatures, times, and so forth, as used in the specification or claims are to be understood as being modified by the term “about.” Accordingly, unless otherwise implicitly or explicitly indicated, or unless the context is properly understood by a person skilled in the art to have a more definitive construction, the numerical parameters set forth are approximations that may depend on the desired properties sought and/or limits of detection under standard test conditions/methods, as known to those skilled in the art. When directly and explicitly distinguishing embodiments from discussed prior art, the embodiment numbers are not approximates unless the word “about” is recited. Whenever “substantially,” “approximately,” “about,” or similar language is explicitly used in combination with a specific value, variations up to and including 10% of that value are intended, unless explicitly stated otherwise.
Directions and other relative references may be used to facilitate discussion of the drawings and principles herein but are not intended to be limiting. For example, certain terms may be used such as “inner,” “outer,” “upper,” “lower,” “top,” “bottom,” “interior,” “exterior,” “left,” right,” “front,” “back,” “rear,” and the like. Such terms are used, where applicable, to provide some clarity of description when dealing with relative relationships, particularly with respect to the illustrated embodiments. Such terms are not, however, intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” part can become a “lower” part simply by turning the object over. Nevertheless, it is still the same part, and the object remains the same.
As used herein, “comprising” means “including,” and the singular forms “a” or “an” or “the” include plural references unless the context clearly dictates otherwise. The term “or” refers to a single element of stated alternative elements or a combination of two or more elements unless the context clearly indicates otherwise.
Although there are alternatives for various components, parameters, operating conditions, etc. set forth herein, that does not mean that those alternatives are necessarily equivalent and/or perform equally well. Nor does it mean that the alternatives are listed in a preferred order, unless stated otherwise. Unless stated otherwise, any of the groups defined below can be substituted or unsubstituted.
Unless explained otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one skilled in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, suitable methods and materials are described below. The materials, methods, and examples are illustrative only and not intended to be limiting. Features of the presently disclosed subject matter will be apparent from the following detailed description and the appended claims.
The following are provided to facilitate the description of various aspects of the disclosed subject matter and to guide those skilled in the art in the practice of the disclosed subject matter.
Fibrous plant material: A portion (e.g., a cut portion, via mechanical means or otherwise) of any photosynthetic eukaryote of the kingdom Plantae in its native state as grown. In some embodiments, the fibrous plant material comprises wood (e.g., hardwood or softwood), bamboo (e.g., any of Bambusoideae, such as but not limited to Moso, Phyllostachys vivax, Phyllostachys viridis, Phyllostachys bambusoides, and Phyllostachys nigra), reed (e.g., any of common reed (Phragmites australis), giant reed (Arundo donax), Burma reed (Neyraudia reynaudiana), reed canary-grass (Phalaris arundinacea), reed sweet-grass (Glyceria maxima), small-reed (Calamagrostis species), paper reed (Cyperus papyrus), bur-reed (Sparganium species), reed-mace (Typha species), cape thatching reed (Elegia tectorum), thatching reed (Thamnochortus insignis), or grass (e.g., a species selected from the Poales order or the Poaceae family). For example, the wood can be any type of hardwood or softwood, such as, but not limited to, basswood, oak, poplar, ash, alder, aspen, balsa wood, beech, birch, cherry, butternut, chestnut, cocobolo, elm, hickory, maple, oak, padauk, plum, walnut, willow, yellow poplar, bald cypress, cedar, cypress, douglas fir, fir, hemlock, larch, pine, redwood, spruce, tamarack, juniper, and yew. Alternatively or additionally, in some embodiments, the plant material can be any type of fibrous plant composed of lignin, hemicellulose, and cellulose. For example, the plant material can be bagasse (e.g. formed from processed remains of sugarcane or sorghum stalks) or straw (e.g., formed from processed remains of cereal plants, such as rice, wheat, millet, or maize).
Contiguous piece: A single continuous piece of fibrous plant material (e.g., a continuous piece of wood taken from a single tree) and subject to processing, as contrasted with a single piece formed by joining or layering multiple subpieces (e.g., laminate). In some embodiments, the contiguous piece consists essentially of the fibrous plant material (e.g., formed from the single continuous piece of plant material, but optionally including a surface coating or additives, for example, to improve weatherability or provide hydrophobicity).
Lignin characteristics: In some embodiments, lignin characteristics refers to characteristics (e.g., content) of a naturally-occurring or native form of lignin in the fibrous plant material. Modified lignin characteristics can thus refer to characteristics of lignin in a section of fibrous plant material that has been in situ modified (e.g., by chemical reaction with OH−) to depolymerize lignin, with the depolymerized lignin being retained within the plant material. In some embodiments, the lignin content within the modified plant material (e.g., softened plant material) can be at least 90% (e.g., ≥95%) of the lignin content prior to said modification. Lignin content within the fibrous plant material before and after lignin modification can be assessed using known techniques in the art, for example, Laboratory Analytical Procedure (LAP) TP-510-42618 for “Determination of Structural Carbohydrates and Lignin in Biomass,” Version 08-03-2012, published by National Renewable Energy Laboratory (NREL), ASTM E1758-01(2020) for “Standard Test Method for Determination of Carbohydrates in Biomass by High Performance Liquid Chromatography,” published by ASTM International, and/or Technical Association of Pulp and Paper Industry (TAPPI), Standard T 222-om-83, “Standard Test Method for Acid-Insoluble Lignin in Wood,” all of which are incorporated herein by reference.
Moisture content: The amount of fluid, typically water, retained within the microstructure of the plant material. In some embodiments, the moisture content (MC) can be determined by oven-dry testing, for example by calculating the change in weight achieved by oven drying (e.g., at 103° C. for 6 hours) the plant material, using the equation:
Alternatively or additionally, moisture content can be assessed using known techniques in the art, for example, an electrical moisture meter or other techniques disclosed in ASTM D4442-20 (2020) for “Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-based Materials,” published by ASTM International, which standard is incorporated herein by reference.
Longitudinal growth direction (L): A direction along which a plant (e.g., tree) grows from its roots or from a main body thereof (e.g., direction L for trunk 202 from tree 200 in
Radial growth direction (R): A direction that extends from a center portion of the fibrous plant material outward (e.g., direction R for trunk 202 from tree 200 in
Tangential growth direction (T) or circumferential direction: A direction perpendicular to both the longitudinal and radial directions in a particular cut of fibrous plant material (e.g., direction T for trunk 202 from tree 200 in
Elasticity: Ability of modified plant material (consisting essentially of plant material, plant material with one or more coatings, or a composite of plant material filled with a polymer) to resist a compressive force and to return to its original shape and size when that force is removed. In some embodiments, modified plant material subjected to a microstructure-preserving drying process (e.g., freeze-drying, solvent exchange, and/or critical point drying) may be substantially elastic along the tangential direction only, while being substantially inelastic along the radial and longitudinal directions.
Black liquor: An aqueous solution of lignin residues, hemicellulose, and other inorganic chemicals employed in the processing of the natural plant material (e.g., modification of the lignin of the natural plant material to form a softened plant material).
Self-densification: Densification of a softened plant material that results from drying (e.g., air-drying) of the softened plant material, for example, from a moisture content greater than 30 wt % (e.g., 30-50 wt %, inclusive) to a moisture content less than 10 wt % (e.g., 3-8 wt %, inclusive). In some embodiments, the self-densification can be performed without any external pressing or with only minimal compression (e.g., less than or equal to 100 kPa). In some embodiments, the self-densification can be performed using a mold, clamp, or other structure designed to constrain a shape of the softened plant material as it dries, for example, to avoid, or at least reduce, any curving, bending, or other undesirable shape change of the plant material induced by the drying.
Embodiments of the disclosed subject matter provide methods for modification of lignin of natural fibrous plant materials, for example, to allow densification thereof, and structures formed from such lignin-modified fibrous plant materials. For example, during an infiltration stage 102 as shown in
Upon activation (e.g., via heating at an elevated temperature, such as 80-180° C.), the infiltrated chemicals can modify the native lignin in situ. For example, during an activation stage 118 as shown in
In some embodiments, a width, W1, of the natural fibrous plant material 104 can be at least 2 times (e.g., at least 3-5 times) a width, W2, of the densified plant material 130. In addition, the densified plant material can have an increased density as compared to the natural fibrous plant material. For example, the densified plant material may have a density of at least 1.15 g/cm3 (e.g., at least 1.2 g/cm3, or at least 1.3 g/cm3), while the natural fibrous plant material may have a density less than 1.0 g/cm3 (e.g., less than 0.9 g/cm3, or less than 0.5 g/cm3).
In some embodiments, the infiltrated chemicals can comprise a chemical that produces hydroxide (OH−) ions in solution, for example, an alkaline chemical. Since long-term exposure of fibrous plant material to alkali can degrade the cellulose (which in turn can lead to a reduction in mechanical properties), the amount of chemicals infiltrated and/or the duration of the heating can be selected to ensure all of the alkaline chemicals within the fibrous plant material are completely reacted to obtain a neutral softened plant material. For example, after heating, some liquid 134 can be squeezed from the fibrous plant material 130 to measure the pH to determine whether the alkali has completely reacted. But such extruded liquid 134 (if any) mainly contains some inorganic salts as well as degradation products of cellulose and hemicellulose, but not black liquor. Alternatively, in some embodiments, the softened plant material can be subject to drying (e.g., air drying) after the activation stage 118 but prior to the densification stage 128, for example, to reduce a moisture content of the softened plant material and thereby avoid, minimize, or at least reduce, the production of liquid 134 during the pressing. Since excessive drying may result in a rigid or inflexible structure for the plant material that would be incompatible with densification, in some embodiments, the pre-drying can be effective to reduce a moisture content to greater than 10 wt %, for example, in a range of 10-20 wt %, inclusive (e.g., ˜15 wt %). In some embodiments, the plant material 130 after densification can have a moisture content less than 8-10 wt %, for example, in a range of 3-8 wt %, inclusive (e.g., 4-6 wt %, inclusive).
After pressing or when the fibrous plant material is otherwise subsequently dried after the chemical activation that produces the in situ lignin modification, the removal of water can immobilize the degradation products within the modified plant material. Since all (or at least most of) these substances are neutral, long-term exposure does not cause degradation of cellulose, thereby ensuring improved mechanical properties of the processed plant material. In conventional delignification, a washing step after chemical treatment is necessary, since the pH of the delignified plant material is generally higher than 13, and the delignified plant material has to be washed to achieve a neutral pH. This not only consume significant amounts of water (and thereby generates significant amounts of wastewater) but also requires substantial processing time (e.g., 72 hours to wash an 8″×4″×2.5″ block of wood). In contrast, embodiments of the disclosed subject matter avoid, or at least reduce, generation of wastewater by consuming the chemicals in the lignin modification of the fibrous plant material.
Since all chemicals are consumed to produce the in situ lignin modification, the resulting softened plant material can exhibit a neutral pH. Moreover, the production of black liquor and other wastewater can be avoided, minimized, or at least reduced as compared to conventional delignification processes. In addition, the products of degradation of the native hemicellulose and lignin are all immobilized inside the channels of the softened plant material. In other words, the processing via infiltrated alkaline chemical can modify the lignin and hemicellulose within the fibrous plant material, but without otherwise removing the lignin and hemicellulose from the fibrous plant material. As a result, the chemical content and composition of the processed plant material can be substantially the same as the starting natural plant material.
In some embodiments, the in situ lignin modification can result in a reduction in lignin content of the processed plant material by no more than 10%. For example, a content of modified lignin (e.g., on a wt % basis) in the processed plant material (e.g., softened plant material and/or densified plant material) can be at least 90% (e.g., at least 95%) of a content of the native lignin originally in the natural plant material. For example, after the in situ modification, the processed plant material can have a lignin content greater than or equal to 25 wt % for softwood, greater than or equal to 20 wt % for hardwood, or greater than or equal to 26 wt % for bamboo. Alternatively or additionally, in some embodiments, the in situ modification can result in a reduction in hemicellulose content of the processed plant material by no more than 10%. For example, a content of modified hemicellulose (e.g., on a wt % basis) in the processed plant material (e.g., softened plant material and/or densified plant material) can be at least 90% (e.g., at least 95%) of a content of the native hemicellulose originally in the natural plant material.
As noted above, in some embodiments, the natural fibrous plant material can be natural wood. Natural wood has a unique three-dimensional porous microstructure comprising and/or defined by various interconnected cells. For example,
The cut direction of the original piece of wood can dictate the orientation of the cell lumina in the final structure. For example, in some embodiments, a piece of natural wood can be cut from a trunk 202 of tree 200 in a vertical or longitudinal direction (e.g., parallel to longitudinal wood growth direction, L) such that lumina of longitudinally-extending cells are oriented substantially parallel to a major face (e.g., largest surface area) of the longitudinal-cut wood piece 206. In the longitudinal-cut wood piece 206, the tangential direction, T, can be substantially perpendicular to the major face. Alternatively, in some embodiments, the piece of natural wood can be cut in a horizontal or radial direction (e.g., perpendicular to longitudinal wood growth direction, L) such that lumina of longitudinally-extending cells are oriented substantially perpendicular to the major face of the radial-cut wood piece 204. Alternatively, in some embodiments, the piece of natural wood can be cut in a rotation direction (e.g., perpendicular to the longitudinal wood growth direction L and along a circumferential direction of the trunk 202) such that lumina of longitudinal cells are oriented substantially parallel to the major face of the rotary-cut wood piece 208. In some embodiments, the piece of natural wood can be cut at any other orientation between longitudinal, radial, and rotary cuts. In some embodiments, the cut orientation of the wood piece may dictate certain mechanical properties of the final processed wood (e.g., a direction of elasticity only along a tangential direction in the final structure).
Alternatively, in some embodiments, the natural fibrous plant material can be natural bamboo.
Within the culm wall 252, the bamboo exhibits a hierarchical cellular structure with porous cells that provide nutrient transport and dense cells that provide mechanical support. For example,
Each vessel 266 can define an open lumen that extends along the longitudinal direction L. Moreover, the elementary fibers that form the fiber bundles 268 may also have irregular small lumina in a center thereof. The fiber bundles 268, parenchyma cells 264, and vessels 266 adhere to each other via a polymer matrix composed of lignin and hemicellulose. The native microstructure can also exhibit pit apertures on the longitudinal walls of fibers, porosity introduced by the parenchyma cells, and/or open intercellular space between adjacent fibers. Embodiments of the disclosed subject matter can in situ modify this natural polymer matrix in order to soften the bamboo for densification and/or further processing.
In some embodiments, the alkali chemical infiltrated into the fibrous plant material can react with the native lignin to cause modification thereof. For example, in some embodiments, the native lignin can be modified to break the lignin macromolecular chain into segments. As shown in
Alternatively or additionally, in some embodiments, the alkali chemical infiltrated into the fibrous plant material can react with native hemicellulose to cause modification (e.g., degradation) thereof. For example, as shown in
Alternatively or additionally, in some embodiments, the alkali chemical infiltrated into the fibrous plant material can react with native cellulose to cause modification (e.g., degradation) thereof. For example, as shown in
The method 400 can proceed to process block 404, where the piece of natural fibrous plant material can be infiltrated with one or more chemicals to modify lignin therein. For example, in some embodiments, the infiltration can be by soaking the piece of natural fibrous plant material in a solution containing the one or more chemicals under vacuum. In some embodiments, the chemical solution can contain at least one chemical component that has OH-ions or is otherwise capable of producing OH− ions in solution. In some embodiments, one, some, or all of the chemicals in the solution can be alkaline. In some embodiments, the chemical solution includes p-toluenesulfonic acid, NaOH, LiOH, KOH, Na2O, or any combination thereof. Exemplary combinations of chemicals can include, but are not limited to, p-toluenesulfonic acid, NaOH, NaOH+Na2SO3/Na2SO4, NaOH+Na2S, NaHSO3+SO2+H2O, NaHSO3+Na2SO3, NaOH+Na2SO3, NaOH/NaH2O3+AQ, NaOH/Na2S+AQ, NaOH+Na2SO3+AQ, Na2SO3+NaOH+CH3OH+AQ, NaHSO3+SO2+AQ, NaOH+Na2Sx, where AQ is Anthraquinone, any of the foregoing with NaOH replaced by LiOH or KOH, or any combination of the foregoing.
For example, in some embodiments, the piece of fibrous plant material (e.g., basswood) can be immersed in a chemical solution (e.g., 2-5% NaOH) in a container. The container can then be placed in a vacuum box and subjected to vacuum. In this way, the air in the fibrous plant material can be drawn out and form a negative pressure. When the vacuum pump is turned off, the negative pressure inside the fibrous plant material can suck the solution into the fibrous plant material through the natural channels therein (e.g., lumina defined by longitudinal cells). The process can be repeated more than once (e.g., 3 times), such that the channels inside the fibrous plant material can be filled with the chemical solution (e.g., about 2 hours). After this process, the moisture content can increase from ˜10.2% (e.g., for natural wood) to ˜70% or greater. In some embodiments, the chemical infiltration can be performed without heating, e.g., at room temperature (20-30° C., such as ˜22-23° C.). In some embodiments, the chemical solution is not agitated in order to avoid disruption to the cellulose-based microstructure of the fibrous plant material.
The method 400 can proceed to process block 406, where the modification may be activated by subjecting the infiltrated piece of fibrous plant material to an elevated temperature, for example, greater than 80° C. (e.g., 80-180° C., such as 120-160° C.), thereby resulting in a softened fibrous plant material (e.g., softened as compared to the native fibrous plant material). In some embodiments, the subjecting to an elevated temperature of process block 406 can be achieved via steam heating, for example, via steam generated in an enclosed reactor, via a steam flow in a flow-through reactor, and/or via steam from a superheated steam generator. Alternatively or additionally, in some embodiments, the subjecting to an elevated temperature of process block 406 can be achieved via dry heating, for example, via conduction and/or radiation of heat energy from one or more heating elements without separate use of steam. In some embodiments, during process block 406, infiltrated piece of fibrous plant material can be subjected to the elevated temperature for a first time period of, for example, 1-5 hours (e.g., depending on the size of the fibrous plant material, with thicker pieces requiring longer heating times). In some embodiments, after the first time period, any steam generated by heating of the infiltrated piece of fibrous plant material can be released, for example, by opening a pressure release (e.g., relief valve) of the reactor. For example, in some embodiments, the pressure release can be effective to remove ˜50% of moisture in the modified plant material. For example, in some embodiments, the now softened plant material can have a moisture content in a range of 30-50 wt %, inclusive.
After process block 406, the method 400 can proceed to decision block 407, where it is determined if the softened plant material should be subject to pre-drying before the further processing, for example, to avoid or at least reduce any waste liquid produced during a final densification process. If pre-drying is desired, the method 400 can proceed to process block 408, where the softened plant material can be subject to pre-drying. In some embodiments, the pre-drying can comprise an air-drying process, for example, allowing the softened fibrous plant material to naturally dry in static or moving air, which air may be at any temperature, such as room temperature (e.g., ˜22-23° C.) or at an elevated temperature (e.g., greater than 23° C.). Alternatively or additionally, the drying can include any of conductive, convective, and/or radiative heating processes, including but not limited to an air-drying process, a vacuum-assisted drying process, an oven drying process, a freeze-drying process, a critical point drying process, a microwave drying process, or any combination of the above. In some embodiments, the pre-drying may be effective to reduce the moisture content of the softened plant material, but without removing too much moisture that the plant material loses its softened nature (e.g., such that the moisture content is greater than or equal to ˜8-10 wt %). In some embodiments, the pre-drying may be effective to reduce a moisture content of the plant material from greater than 30 wt % (e.g., 30-50 wt %) to within a range of, for example, 10-20 wt % (e.g., ˜15 wt %). While moisture may be removed from the softened plant material via the heating and/or pre-drying (e.g., via evaporation), the removed moisture may be substantially free of residual salts and/or chemicals from the in situ lignin-modification. Rather, in some embodiments, the chemicals can be substantially consumed by the modification, and the residual salts can be retained within the microstructure of the softened plant material.
After process block 408, or if pre-drying was not desired at decision block 407, the method 400 can proceed via decision block 409 to further processing of the softened plant material depending on one or more desired applications. In some embodiments, the softened plant material can be subject to densification at process block 410, for example, to produce densified fibrous plant material having a high strength (e.g., greater than 500 MPa, such as ˜560 MPa). In some embodiments, the densification or other associated processing can be, for example, as described in U.S. Publication No. 2020/0223091, published Jul. 16, 2020 and entitled “Strong and Tough Structural Wood Materials, and Methods for Fabricating and Use Thereof,” or International Publication No. WO 2021/108576, published Jun. 3, 2021 and entitled “Bamboo Structures, and Methods for Fabrication and Use Thereof,” each of which is incorporated herein by reference. Alternatively or additionally, the softened plant material can be subject to molding at process block 430, for example, to produce 3-D moldable or 3-D molded plant material. In some embodiments, the molding or other associated processing can be, for example, as described in International Publication No. WO 2021/216803, published Oct. 28, 2021 and entitled “Moldable and Molded Cellulose-based Structural Materials, and Systems and Methods for Forming and Use Thereof,” which is incorporated herein by reference. Alternatively or additionally, the softened plant material can be subject to drying at process block 460 to form a flexible structure or an anisotropically-elastic structure. In some embodiments, the drying or other associated processing can be, for example, as described in U.S. Publication No. 2020/0282591, published Sep. 10, 2020 and entitled “Flexible Wood Structures and Devices, and Methods for Fabricating and Use Thereof,” or pending International Application No. PCT/US22/31289, filed May 27, 2022 and entitled “Wood Materials Having Anisotropic Elasticity, and Methods for Fabrication and Use Thereof,” each of which is incorporated herein by reference. Alternatively or additionally, the softened plant material can be subject to drying at process block 470 to form a densified structure, for example, a self-densified fibrous plant material having a high strength (e.g., greater than 300 MPa, such as ˜304 MPa).
After method 400, the processed fibrous plant material can be used in a particular application or adapted for use in a particular application. For example, the modified plant product can be subjected to further processing, such as machining, cutting, or otherwise forming the contiguous piece into a particular shape. The use of the modified plant product can involve use of the modified plant product by itself or assembling it together with different plant species (conventional, modified, or otherwise) and/or non-plant materials (e.g., metal, metal alloy, plastic, ceramic, composite, etc.) to form a heterogenous composite structure.
Although some of blocks 402-410, 430, 460, and 470 of method 400 have been described as being performed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. In addition, although blocks 402-410, 430, 460, and 470 of method 400 have been separately illustrated and described, in some embodiments, process blocks may be combined and performed together (simultaneously or sequentially). Moreover, although
Since all chemicals are consumed in process blocks 402-406, the resulting softened plant material can exhibit a neutral pH. Moreover, unlike prior delignification processes, no or minimal black liquor can be produced by process blocks 402-406, and the products of degradation of the native cellulose, hemicellulose, and lignin can all be immobilized inside the channels of the softened plant material.
Referring to
Alternatively or additionally, in some embodiments, the internal modification can include performing a further chemical treatment that modifies the surface chemistry of the softened plant material. For example, in some embodiments, the further chemical treatment can provide weatherability or corrosion resistance can include at least one of cupramate (CDDC), ammoniacal copper quaternary (ACQ), chromated copper arsenate (CCA), ammoniacal copper zinc arsenate (ACZA), copper naphthenate, acid copper chromate, copper citrate, copper azole, copper 8-hydroxyquinolinate, pentachlorophenol, zinc naphthenate, copper naphthenate, creosote, titanium dioxide, propiconazole, tebuconazole, cyproconazole, boric acid, borax, organic iodide (IPBC), and Na2B8O13·4H2O.
Alternatively or additionally, in some embodiments, the internal modification of process block 412 can include infiltrating the softened plant material with one or more polymers (or polymer precursors). For example, the softened plant material can be immersed in a polymer solution under vacuum to form a hybrid material. The polymer can be any type of polymer capable of infiltrating into the pores of the softened plant material, for example, a synthetic polymer, a natural polymer, a thermosetting polymer, or a thermoplastic polymer. For example, in some embodiments, the polymer can be epoxy resin, polyvinyl alcohol (PVA), polyethylene glycol (PEO), polyamide (PA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyacrylonitrile (PAN), polycaprolactam (PA6), poly(m-phenylene isophthalamide) (PMIA), poly-p-phenylene terephthalamide (PPTA), polyurethane (PU), polycarbonate (PC), polypropylene (PP), high-density polyethylene (HDPE), polystyrene (PS), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), poly(butylene succinate-co-butylene adipate) (PBSA), polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(glycolic acid) (PGA), polypyrrole (PPy), polythiophene (PTh), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylene vinyl alcohol (EVOH), poly(vinylidene chloride) (PVDC), polyxylylene adipamide (MXD6), polyethylene (PE), polyvinyl chloride (PVC), poly(methyl methacrylate) (PMMA), acrylonitrile butadiene styrene (ABS), polyimide (PI), polyethylenimine (PEI), polylactic acid (PLA), octadecyl trichlorosilane (OTS), polyoctahedral silsesquioxane (POSS), paramethylstyrene (PMS), polydimethylsiloxane (PDMS), poly(ethylene naphthalate (PEN), a graft copolymer of acrylonitrile-butadiene-styrene-methylmethacrylate (ABSM), dodecyltrimethoxysilane (DTMS), rosin, chitin, chitosan, protain, plant oil, lignin, hemicellulose, carboxymethyl cellulose, cellulose acetate, starch, agar, or any combination of the above.
The method 410 can proceed to process block 414, where the softened plant material is pressed in a direction crossing its longitudinal direction. In some embodiments, the pressing can be in a direction substantially perpendicular to the longitudinal direction, while in other embodiments the pressing may have a force component perpendicular to the longitudinal direction. In either case, the pressing can be effective to reduce a thickness of the softened plant material, thereby increasing its density as well as collapsing (at least partially) the natural lumina (e.g., vessels, lumen in each fiber, parenchyma cells, etc.), voids, and/or gaps within the cross-section of the softened plant material. In some embodiments, the pressing can be along a single direction (e.g., along radial direction R), for example, to reduce a thickness of the softened plant material (e.g., at least a 5:2 reduction in dimension as compared to the softened plant material prior to pressing). Alternatively or additionally, in some embodiments, the softened plant material can be simultaneously pressed in two directions (e.g., along radial direction R and a second direction perpendicular to both the radial direction R and the longitudinal direction L), for example, to reduce a cross-sectional area of the softened plant material (e.g., to produce a densified rectangular bar). Alternatively or additionally, in some embodiments, the softened plant material can be sequentially pressed in different directions (e.g., first along radial direction R and then along a second direction perpendicular to the radial direction R and longitudinal direction L).
In some embodiments, the pressing may be performed without any prior drying of the softened plant material or with the softened plant material retaining at least some water or other fluid therein. The pressing can thus be effective to remove at least some water or other fluid from the softened plant material at the same time as its dimension is reduced and density increased. In some embodiments, a separate drying process can be combined with the pressing process. For example, the softened plant material may initially be pressed to cause densification and remove at least some water or fluid therefrom, followed by a drying process (e.g., air drying) to remove the remaining water or fluid. Alternatively, in some embodiments, the softened plant material may initially be dried to remove at least some water or fluid therefrom (e.g., initial drying in a humidity chamber followed by air drying at room temperature, such that the moisture content of the plant material approaches but remains greater than 15 wt %, for example, 10 wt %), followed by pressing to cause densification (and potentially further removal of water or other fluid, for example, a moisture content less than 10 wt %, such as 3-8 wt %).
In some embodiments, the pressing can encourage hydrogen bond formation between the cellulose-based fibers of the cell walls of the softened plant material, thereby improving mechanical properties of the densified plant material. Moreover, any particles or materials formed on surfaces of the softened plant material or within the softened plant material (e.g., via the internal modification of process block 414) can be retained after the pressing, with the particles/materials on internal surfaces being embedded within the collapsed lumina and intertwined cell walls.
The pressure and timing of the pressing can be a factor of the size of softened plant material prior to pressing, the desired size of the plant material after pressing, the water or fluid content within the softened plant material (if any), the temperature at which the pressing is performed, relative humidity, the characteristics of material (e.g., infiltrated polymer) from the internal modification (if any), and/or other factors. For example, the softened plant material can be held under pressure for a time period of at least 1 minute to up to several hours (e.g., 1-180 minutes, inclusive). In some embodiments, the softened plant material can be held under pressure for 3-72 hours, inclusive. In some embodiments, the pressing can be performed at a pressure between 0.5 MPa and 20 MPa, inclusive, for example, 5 MPa. In some embodiments the pressing may be performed without heating (e.g., cold pressing), while in other embodiments the pressing may be performed with heating (e.g., hot pressing). For example, the pressing may be performed at a temperature between 20° C. and 160° C., e.g., greater than or equal to 100° C.
The method 410 can proceed to optional process block 416, where the densified plant material may be subject to an external modification. Although the term “external” is used to refer to the modification of process block 416, it is contemplated that, in some embodiments, the modification may be applied to internal features as well as external features of the densified plant material, while in other embodiments the modification may be applied to either internal features or external features of the densified plant material without otherwise affecting the other feature. In some embodiments, the external modification can include forming, depositing, or otherwise providing a coating on one or more external surfaces of the densified plant material. The coating may imbue the densified plant material with certain advantageous properties, such as but not limited to hydrophobicity, weatherability, corrosion resistance (e.g., salt water resistant), and/or flame resistance. For example, the coating can comprise an oil-based paint, a hydrophobic paint, a polymer coating, and/or a fire-resistant coating. In some embodiments, the fire-resistant coating can include nanoparticles (e.g., boron nitride nanoparticles). Alternatively or additionally, in some embodiments, a coating for the bamboo can include boron nitride (BN), montmorillonite clay, hydrotalcite, silicon dioxide (SiO2), sodium silicate, calcium carbonate (CaCO3), aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), magnesium carbonate (MgCO3), aluminum sulfate, iron sulfate, zinc borate, boric acid, borax, triphenyl phosphate (TPP), melamine, polyurethane, ammonium polyphosphate, phosphate, phosphite ester, ammonium phosphate, ammonium sulfate, phosphonate, diammonium phosphate (DAP), ammonium dihydrogen phosphate, monoammonium phosphate (MAP), guanylurea phosphate (GUP), guanidine dihydrogen phosphate, antimony pentoxide, or any combination of the above.
The method 410 can proceed to process block 418, where the densified plant material can be machined, cut, and/or otherwise physically manipulated (e.g., bending) in preparation for eventual use. Machining processes can include, but are not limited to, cutting (e.g., sawing), drilling, woodturning, tapping, boring, carving, routing, sanding, grinding, and abrasive tumbling. Manipulating process can include, but are not limited to, bending, molding, and other shaping techniques.
The method 410 can proceed to process block 420, where the densified plant material can be used in a particular application. For example, the densified plant material can be adapted for use as structural material (e.g., a load bearing component or a non-load bearing component). For example, the densified plant material can have a mechanical strength (e.g., tensile strength) of at least 500 MPa. Other applications beyond those specifically listed are also possible for the densified plant material. Indeed, one of ordinary skill in the art will readily appreciate that the densified plant materials disclosed herein can be adapted to other applications based on the teachings of the present disclosure.
Although blocks 412-420 of method 410 have been described as being performed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. In addition, although blocks 412-420 of method 410 have been separately illustrated and described, in some embodiments, process blocks may be combined and performed together (simultaneously or sequentially). Moreover, although
Referring to
The drying of either process block 434 or process block 436 can include any of conductive, convective, and/or radiative heating processes, including but not limited to an air-drying process, a vacuum-assisted drying process, an oven drying process, a freeze-drying process, a critical point drying process, a microwave drying process, or any combination of the above. For example, an air-drying process can include allowing the softened fibrous plant material to naturally dry in static or moving air, which air may be at any temperature, such as room temperature (e.g., 23° C.) or at an elevated temperature (e.g., greater than 23° C.). For example, a vacuum-assisted drying process can include subjecting the softened fibrous plant material to reduced pressure, e.g., less than 1 bar, for example, in a vacuum chamber or vacuum oven. For example, an oven drying process can include using an oven, hot plate, or other conductive, convective, or radiative heating apparatus to heat the softened fibrous plant material at an elevated temperature (e.g., greater than 23° C.), for example, 70° C. or greater. For example, a freeze-drying process can include reducing a temperature of the softened fibrous plant material to below a freezing point of the fluid therein (e.g., less than 0° C.), then reducing a pressure to allow the frozen fluid therein to sublime (e.g., less than a few millibars). For example, a critical point drying process can include immersing the softened fibrous plant material in a fluid (e.g., liquid carbon dioxide), increasing a temperature and pressure of the softened fibrous plant material past a critical point of the fluid (e.g., 7.39 MPa, 31.1° C. for carbon dioxide), and then gradually releasing the pressure to remove the now gaseous fluid. For example, a microwave drying process can include using a microwave oven or other microwave generating apparatus to induce dielectric heating within the softened fibrous plant material by exposing it to electromagnetic radiation having a frequency in the microwave regime (e.g., 300 MHz to 300 GHz), for example, a frequency of ˜915 MHz or ˜2.45 GHz.
In some embodiments, the full drying of process block 436 causes shrinkage of the softened fibrous plant material, which in turn causes significant buckling of the cell walls. In some embodiments, the lumina formed by the longitudinal cells may collapse (e.g., fully collapse such that facing surface of the channel wall are in contact, or at least significantly narrow). After the drying of process block 436, the method 430 can proceed to process block 438, where the dried softened fibrous plant material is rehydrated using a fluid shock technique. For example, the dried softened fibrous plant material can be partially or fully immersed in a fluid (e.g., water, alcohol, or any combination thereof) for a short period of time (e.g., several minutes, such as 3 minutes or less, for example, on the order of seconds) such that the rehydrated material has a moisture content of at least 35 wt % (e.g., around 50 wt %). Methods for rehydration other than immersion in fluid are also possible according to one or more embodiments. For example, rehydration can be achieved by exposure to a humidified environment.
In some embodiments, the rehydration is effective to re-swell the cells wall and allow larger lumina (e.g., vessels) to re-open while smaller lumina (e.g., fiber cells) to remain substantially collapsed. The swelling introduced by the fluid shock can create wrinkles in the cell wall structure, which can allow the softened fibrous plant material to accommodate severe tension and compression without damage.
With the softened fibrous plant material having a moisture content of at least 35 wt % after either process block 434 or process block 438, the method 430 can proceed to decision block 440, where it is determined if a pre-shaping modification is desired. If such a modification is desired, the method 430 can proceed to process block 442, where a non-machining technique (e.g., without removing substantive amounts of material to form the modification) is used to form a hole, opening, recess, or other surface modification. The modification can be made while the moisture content of the softened fibrous plant material is at least 35 wt % and therefore in a substantially flexible/moldable state. As a result, the cellulose fibers may retain sufficient motility so as to bend around the formation of the hole, opening, or recess without breaking.
After the modification of process block 442, or if no modification was desired at decision block 440, the method 430 can proceed to process block 444, where the softened fibrous plant material can be shaped to have a desired configuration, such as a 3-D configuration. The shaping of process block 444 can include bending, folding, pushing, pressing, molding (e.g., using a mold) or otherwise non-destructively forming (e.g., no removal of material) the softened fibrous plant material to have the desired configuration. During the shaping, the moisture content of the softened fibrous plant material is at least 35 wt % and therefore in a substantially flexible/moldable state. As a result, the softened fibrous plant material readily adopts the shaped configuration and can return to its original unshaped configuration without damage.
The method 400 can proceed to decision block 446, where it is determined if the softened fibrous plant material should be set in the shaped configuration or if the softened fibrous plant material should instead be maintained in a flexible/moldable state. If it is desired to maintain the softened fibrous plant material as moldable material, the method 430 can proceed to process block 448, where the moisture content thereof is maintained at or above 35 wt %. Otherwise, if it is desired to set the softened fibrous plant material in the shaped configuration, the method 430 can proceed to process block 450, where the softened fibrous plant material can be fully dried while maintaining the shaped configuration, such that the moisture content thereof is reduced to at or below 15 wt % (e.g., in a range of 3-8 wt %). The drying of process block 450 may be performed in a manner similar to that described above with respect to process block 436. Alternatively or additionally, in some embodiments, the drying can be a by-product of the shaping, for example, by using a hot press to simultaneously mold and dry the softened fibrous plant material. In such embodiments, the shaping can be effective to further densify the softened fibrous plant material prior to fully drying, which densification may further improve the mechanical properties of the molded material. Once fully dried, the fibrous plant material may be rigid and incapable of further shape manipulation without plastic deformation, thereby forming a molded structure.
In some embodiments, the method 430 can proceed from process block 448 or process block 450 to optional process block 452, where an external modification may be applied. For example, the fibrous plant material can be sealed to prevent ingress of moisture or egress of moisture and thereby maintaining a desired moldable (e.g., flexible) or molded (e.g., rigid) state of the material. In some embodiments, the sealing is by placing the fibrous plant material in a sealed or controlled environment. Alternatively or additionally, the sealing can be achieved by a protective layer or coating provided over exposed surfaces of the fibrous plant material. For example, the protecting layer or coating can be a polyurethane coating, paint, silane hydrophobic coating, or any other coating effective to prevent, or at least restrict, movement of moisture into or out of the fibrous plant material. Alternatively or additionally, the external modification can include a destructive modification, for example, machining or cutting to prepare the lignin-modified fibrous plant material for subsequent use.
The method 430 can proceed to process block 454, where the lignin-modified fibrous plant material, in either the moldable state or molded state, can be used in a particular application or adapted for use in a particular application. In some embodiments, the molded lignin-modified fibrous plant material can be used as a structural material, for example, assembled together with non-plant materials (e.g., metal, metal alloy, plastic, ceramic, composite, etc.) to form a heterogenous composite structure. Alternatively, in some embodiments, the moldable lignin-modified fibrous plant material can be used as a flexible substrate or structure, for example, as a scaffold for robotic actuation or a substrate for electronics.
Although some of blocks 432-454 of method 430 have been described as being performed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. In addition, although blocks 432-454 of method 430 have been separately illustrated and described, in some embodiments, process blocks may be combined and performed together (simultaneously or sequentially). For example, as noted above, the drying of process block 450 and the shaping of process block 444 may occur simultaneously. Moreover, although
Referring to
In some embodiments, after the drying, the lignin-modified fibrous plant material can be elastic at least along its tangential direction, for example, due at least in part to removal of ray cells. In some embodiments, the lignin-modified fibrous plant material can remain inelastic along its radial and longitudinal directions, for example, due at least in part to retention of the longitudinal cells. In such embodiments, the dried lignin-modified fibrous plant material can exhibit asymmetric elasticity or anisotropic elasticity (e.g., substantially elastic along tangential direction, T, and substantially inelastic along radial direction, R, and longitudinal direction, L). Alternatively, in some embodiments, after the drying, the lignin-modified fibrous plant material can be flexible (e.g., isotropically or anisotropically).
The method 460 can proceed to optional process block 464, where the lignin-modified fibrous plant material can optionally be subjected to one or more modifications. In some embodiments, the optional modification can comprise sealing the dried, lignin-modified fibrous plant material, for example, to prevent ingress of moisture or egress of moisture. For example, the sealing can be by placing the lignin-modified fibrous plant material in a sealed or controlled environment. Alternatively or additionally, the sealing can be achieved by a protective layer or coating provided over exposed surfaces of the lignin-modified fibrous plant material. For example, the protecting layer or coating can be a polyurethane coating, paint, silane hydrophobic coating, or any other coating effective to prevent, or at least restrict, movement of moisture into or out of the lignin-modified fibrous plant material. Alternatively or additionally, the optional modification can include a destructive modification, for example, machining or cutting to prepare the lignin-modified fibrous plant material for subsequent use.
In some embodiments, the optional modification can include applying a coating to external surfaces and/or internal surfaces of the lignin-modified fibrous plant material, and/or coupling particles to the external surfaces and/or internal surfaces of the lignin-modified fibrous plant material. In some embodiments, the coating can have a thickness less than or equal to 10 μm, for example, in a range of 10 nm-10 μm, inclusive. In some embodiments, the coating may be such that the porosity of the lignin-modified fibrous plant material remains at least 50%. In some embodiments, the coating or the coupled particles can include a conductive material, a semiconductive material, or an insulating material. For example, the coating or the coupled particles can include nanoparticles, nanowires, graphene, graphite, ceramic oxide, single-walled carbon nanotubes (CNTs), double-walled CNTs, multi-walled CNTs, polyaniline, carbon black, graphite, hard carbon (e.g., char or non-graphitizing carbon), reduced graphene oxide, graphene, plasmonic metallic nanoparticles, catalytic nanoparticles, electroactive nanoparticles, metal alloy nanoparticles, semiconductor nanoparticles, sulfides, phosphides, borides, oxides, or any combination of the foregoing. Examples of materials for the plasmonic metallic nanoparticles include but are not limited to Au, Pt. Ag, Pd, and Ru. The metallic nanoparticles and the metal alloy nanoparticles can include, but are not limited to, Pt, Pd. Au, Ag, Ni, Co, Ru, and Fe. Examples of materials for the semiconductor nanoparticles include CuFeSe2 or any other semiconductor. Examples of materials for the sulfides include, but are not limited to, MoS2, CoSx, and FeS2, where x is an integer. Examples of materials for the phosphides include, but are not limited to, CoP, NiP2, and MoPx, where x is an integer. Examples of materials for the borides include, but are not limited to, CoB, MoB, and NiB. Examples of materials for the oxides include, but are not limited to, MnO2, Fe2O3, CoO, and NiO.
Alternatively or additionally, in some embodiments, the coating can comprise a hydrophobic material, a water-resistant material, a weather-resistant material, or any combination of the foregoing. For example, the coating can comprise manganese oxide polystyrene (MnO3/PS) nano-composite, zinc oxide polystyrene (ZnO/PS) nano-composite, precipitated calcium carbonate, carbon nanotube structures, silica nano-coating, fluorinated silanes, polyethylene, polystyrene, polyvinylchloride, polytetrafluorethylene, polydimethylsiloxane, polyester, polyurethane, acrylic, epoxy, or any combination of the foregoing. Alternatively or additionally, the coating can comprise sodium chloride, potassium sulphate, sodium sulphate, calcium sulphate, magnesium sulphate, copper sulphate, sodium nitrate, sodium carbonate, calcium, silicon, phosphorus, silver, titanium oxide, or any combination of the foregoing.
In some embodiments, the optional modification can include infiltrating the lignin-modified fibrous plant material with another elastic or flexible material, such as a polymer (or polymer precursor) or protein, so as to form an elastic composite. In some embodiments, the material can substantially or at least mostly fill the open lumina of the microstructure of the lignin-modified fibrous plant material. In some embodiments, the infiltration may be such that the porosity of the lignin-modified fibrous plant material is reduced to less than or equal to 10%. For example, the elastic or flexible material can be natural or synthetic polyisoprene, polybutadiene, chloroprene rubber (e.g., Baypren®), polychloroprene, neoprene, butyl rubber, halogenated butyl rubber, styrene-butadiene rubber (e.g., copolymer of styrene and butadiene), polydimethylsiloxane (PDMS), nitrile rubber (e.g., copolymer of butadiene and acrylonitrile), hydrogenated nitrile rubber (e.g., Therban®, Zetpol®, etc.), ethylene propylene rubber (e.g., a copolymer of ethene and propene), ethylene propylene diene monomer (EPDM) rubber, epichlorohydrin rubber, polyacrylic rubber, silicon rubber, fluorosilicone rubber, fluoroelastomer (e.g., Viton™, Tecnoflon®, Fluorel™, AFLAS®, DAI-EL™), perfluoroelastomer (e.g., Tecnoflon® PFR, Kalrez®, Chemraz®, Perlast®), polyether block amide, chlorosulfonated polyethylene (e.g., Hypalon®), ethylene-vinyl acetate, thermoplastic elastomer, resilin, elastin, polysulfide rubber, elastolefin, poly(dichlorophosphazene), an inorganic rubber from hexachlorophosphaze polymerization, or any combination of the foregoing.
The method 460 can proceed to process block 466, where the lignin-modified fibrous plant material (or composite) can be used in a particular application or adapted for use in a particular application. In some embodiments, the lignin-modified fibrous plant material (or composite) can be used as an anisotropic resilient structure that can completely recover its original shape after being subjected to a compressive force along its tangential direction (while remaining substantially inelastic along the orthogonal radial and longitudinal directions). In some embodiments, the lignin-modified fibrous plant material (or composite) can be employed as a sound-absorbing or force-absorbing material. In some embodiments, the lignin-modified fibrous plant material can be oriented with its inelastic plane (e.g., along radial and longitudinal directions) to support a force applied to it (e.g., function as a structural member) while its elastic direction (e.g., along the tangential direction) absorbs a force applied to it (e.g., acts as a sound absorbing member).
The lignin-modified fibrous plant material (or composite) can be used in any application where a resilient and/or spongy material may be useful, such as, but not limited to building (construction) or structural materials (e.g., insulation, flooring, etc.), sound absorbers, parts of footwear (e.g., inserts or insoles, outsoles, midsoles, uppers, tongues, etc.), cushioning (e.g., packing materials, mattresses, pillows, cushions, etc.), seals (e.g., gaskets, O-rings, etc.), isolation devices (e.g., damping pad, anti-vibration mounts, etc.), damping elements (e.g., shock absorber), energy storage or harvesting devices, elastic substrates (e.g., flexible conductors, flexible electronic devices, wearable devices, etc.), shape memory structures, and tires. In some embodiments, the lignin-modified fibrous plant material (or composite) can be used as a structural material, for example, assembled together with non-plant materials (e.g., metal, metal alloy, plastic, ceramic, composite, etc.) to form a heterogenous composite structure.
Although blocks 462-466 in
Referring to
The method 470 can proceed to optional process block 474, where the self-densified fibrous plant material can optionally be subjected to one or more modifications. In some embodiments, the optional modification can comprise sealing the densified fibrous plant material, for example, to prevent ingress of moisture or egress of moisture. For example, the sealing can be by placing the densified fibrous plant material in a sealed or controlled environment. Alternatively or additionally, the sealing can be achieved by a protective layer or coating provided over exposed surfaces of densified fibrous plant material. For example, the protecting layer or coating can be a polyurethane coating, paint, silane hydrophobic coating, or any other coating effective to prevent, or at least restrict, movement of moisture into or out of the densified fibrous plant material. Alternatively or additionally, the optional modification can include a destructive modification, for example, machining or cutting to prepare the densified fibrous plant material for subsequent use.
In some embodiments, the optional modification can include applying a coating to external surfaces and/or internal surfaces of the densified fibrous plant material, and/or coupling particles to the external surfaces and/or internal surfaces of the densified fibrous plant material. In some embodiments, the coating can have a thickness less than or equal to 10 μm, for example, in a range of 10 nm-10 μm, inclusive. In some embodiments, the coating or the coupled particles can include a conductive material, a semiconductive material, or an insulating material. For example, the coating or the coupled particles can include nanoparticles, nanowires, graphene, graphite, ceramic oxide, single-walled carbon nanotubes (CNTs), double-walled CNTs, multi-walled CNTs, polyaniline, carbon black, graphite, hard carbon (e.g., char or non-graphitizing carbon), reduced graphene oxide, graphene, plasmonic metallic nanoparticles, catalytic nanoparticles, electroactive nanoparticles, metal alloy nanoparticles, semiconductor nanoparticles, sulfides, phosphides, borides, oxides, or any combination of the foregoing. Examples of materials for the plasmonic metallic nanoparticles include but are not limited to Au. Pt, Ag, Pd, and Ru. The metallic nanoparticles and the metal alloy nanoparticles can include, but are not limited to, Pt, Pd, Au, Ag, Ni, Co, Ru, and Fe. Examples of materials for the semiconductor nanoparticles include CuFeSe2 or any other semiconductor. Examples of materials for the sulfides include, but are not limited to, MOS2, CoSx, and FeS2, where x is an integer. Examples of materials for the phosphides include, but are not limited to, CoP, NiP2, and MoPx, where x is an integer. Examples of materials for the borides include, but are not limited to. CoB, MoB, and NiB. Examples of materials for the oxides include, but are not limited to, MnO2, Fe2O3, CoO, and NiO.
Alternatively or additionally, in some embodiments, the coating can comprise a hydrophobic material, a water-resistant material, a weather-resistant material, or any combination of the foregoing. For example, the coating can comprise manganese oxide polystyrene (MnO3/PS) nano-composite, zinc oxide polystyrene (ZnO/PS) nano-composite, precipitated calcium carbonate, carbon nanotube structures, silica nano-coating, fluorinated silanes, polyethylene, polystyrene, polyvinylchloride, polytetrafluorethylene, polydimethylsiloxane, polyester, polyurethane, acrylic, epoxy, or any combination of the foregoing. Alternatively or additionally, the coating can comprise sodium chloride, potassium sulphate, sodium sulphate, calcium sulphate, magnesium sulphate, copper sulphate, sodium nitrate, sodium carbonate, calcium, silicon, phosphorus, silver, titanium oxide, or any combination of the foregoing.
The method 470 can proceed to process block 476, where the densified plant material can be used in a particular application. For example, the densified plant material can be adapted for use as structural material (e.g., a load bearing component or a non-load bearing component). For example, the densified plant material can have a mechanical strength (e.g., tensile strength) of at least 300 MPa. Other applications beyond those specifically listed are also possible for the densified plant material. Indeed, one of ordinary skill in the art will readily appreciate that the densified plant materials disclosed herein can be adapted to other applications based on the teachings of the present disclosure.
Although blocks 472-476 of method 470 have been described as being performed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. In addition, although blocks 472-476 of method 470 have been separately illustrated and described, in some embodiments, process blocks may be combined and performed together (simultaneously or sequentially). Moreover, although
In some embodiments, the chemically-infiltrated fibrous plant material can be subjected to an elevated temperature (e.g., 80-180° C., such as 120-160° C.) by heating with steam, in order to react the infiltrated chemical with the native lignin and/or hemicellulose in the microstructure of the fibrous plant material, without adding of any additional chemical solutions. In some embodiments, the heating can be for at least 1 hour, for example, 1-5 hours, depending on the size of the fibrous plant material, with thicker pieces requiring longer heating times. In some embodiments, the steam heating can be performed in a pressure reactor, such as reactor 500 of
Alternatively, in some embodiments, the steam heating can be performed using a flow-through reactor, such as reactor 520 of
Alternatively, in some embodiments, the heating can be performed without the use of steam, for example, using conductive and/or radiative heating. In some embodiments, the heating can be such that water loss from the chemically-infiltrated fibrous plant material is minimized, or at least reduced, for example, by performing the heating in a sealed pressure reactor, such as reactor 530 of
Softened wood was prepared by infiltrating a piece of basswood (20 cm×8 cm×2.5 cm) with 3% NaOH. In particular, the basswood was immersed in the 3% NaOH in a container, which was then placed in a vacuum box and subject to vacuum. Air in the wood is thus drawn out and forms a negative pressure within the microstructure. The negative pressure sucks the NaOH into the natural channels of the wood microstructure. The process was repeated three times at room temperature such that the channels were filled with the NaOH solution, which process took about 2 hours to complete. After this process, the moisture content can increase from ˜10.2% to close to 70%, as shown in
To measure chemical compositions of natural wood and softened wood, two wood samples (2.5 cm×2.5 cm×2.5 cm) were first oven-dried at 105° C. overnight. The resulting blocks were then ground using a 4-mesh outlet screen (˜5 mm). This was followed by a second pass using a 20-mesh (˜1 mm) screen. The resulting materials were first hydrolyzed using sulfuric acid in two stages. The hydrolysis conditions were an acid concentration of 72% (v/v) at 30° C. and 3.6% (v/v) at 120° C. for the first and second stages, respectively. The hydrolysis duration time was 1 hour for both stages. The hydrolysate was then analyzed for carbohydrates in an improved high-performance anion exchange chromatographic method using pulsed amperometric detection (HPAEC-PAD). The Klason lignin content was measured gravimetrically after washing and drying the solid residue from the acid hydrolysis. The results of the content measurements are shown in
To obtain densified wood, the softened basswood was subsequently compressed at a pressure of ˜5 MPa and a temperature of ˜120° C. for about ˜20 min to yield a densified wood with improved mechanical properties. For example, as shown in the mechanical test results of
In addition, since the densified wood retains the lignin and hemicellulose of the natural wood as well as the neutralized salts from chemical reaction, the densified wood can have measurable physical differences as compared to densified wood obtained using conventional partial delignification techniques (e.g., immersion in 3% NaOH at 100° C., followed by rinsing, and densification). For example, the color of the densified wood with in situ lignin modification can be visually darker than that of the partially-delignified, densified wood. The reflectance of both wood samples was measured according to ASTM E903-20, entitled “Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres,” and published Oct. 21, 2020, which is incorporated herein by reference. As shown in
To evaluate immobilized contents within the densified wood with in situ lignin modification as compared to partially-delignified, densified wood, the ash content (e.g., indicative of the inorganic content of the densified wood) and the hot water extract (e.g., indicative of components retained in the densified wood) were measured. The ash content (weight of ash as a percentage of the original weight of the densified wood) was measured according to ASTM D2584-18, entitled “Standard Test Method for Ignition Loss of Cured Reinforced Resins,” and published Oct. 8, 2018, ASTM D5630-13, entitled “Standard Test Method for Ash Content in Plastics,” and published Apr. 1, 2014, and ISO 3451-1:2019, entitled “Plastics—Determination of Ash—Part 1: General Methods,” and published February 2019, each of which is incorporated herein by reference. As shown in
The hot water extract (weight of residue after evaporation of water as a percentage of the original weight of the densified wood) was measured according to ASTM D1110-84(2007), entitled “Standard Test Methods for Water Solubility of Wood,” and published Sep. 10, 2013, which is incorporated herein by reference. As shown in
In the in situ lignin modification process, the alkaline chemical (e.g., NaOH) primarily reacts with lignin, hemicellulose, and cellulose in the wood. Thus, the main products of the modification process are organic salts. To evaluate the chemical composition of these salts, the hot water extract solutions (e.g., as obtained for
To avoid production of wastewater (e.g., fluid containing degradation products and/or chemicals from the lignin modification, as opposed to substantially clean fluid vapor that evaporates during drying) during the densification process, some of the moisture in the softened wood after the in situ lignin modification can be removed prior to densification. In another fabricated example, a piece of basswood (10 cm×5 cm×0.5 cm) was infiltrated with 3% NaOH in a manner similar to that described above. The resulting chemical-infiltrated wood had a moisture content of 75 wt %. The chemical-infiltrated wood was then heated using steaming in a manner similar to that described above to yield softened wood. In particular, after the steam heating is completed, the pressure in the reactor was vented, thereby removing ˜50% of the moisture in the sample, such that softened wood has a moisture content of 34.5 wt %. Note that the smaller size of the wood sample allowed more moisture to be introduced during the chemical infiltration step and more moisture to be removed during the steam heating step as compared to the processing of the wood sample of
Softened bamboo was prepared by infiltrating a piece of bamboo with 4% NaOH. The NaOH-infiltrated bamboo was then heated using steam in a pressure reactor (e.g., reactor 500 of
Self-densified wood was prepared by infiltrating a piece of basswood with 3% NaOH. The NaOH-infiltrated basswood was then heated using steam in a pressure reactor (e.g., reactor 500 of
In view of the above-described implementations of the disclosed subject matter, this application discloses the additional examples in the clauses enumerated below. It should be noted that one feature of a clause in isolation, or more than one feature of the clause taken in combination, and, optionally, in combination with one or more features of one or more further clauses are further examples also falling within the disclosure of this application.
Clause 1. A method comprising:
Clause 41. The method of any clause or example herein, in particular, any one of Clauses 19-40, wherein:
Any of the features illustrated or described herein, for example, with respect to
The present application claims the benefit of U.S. Provisional Application No. 63/237,625, filed Aug. 27, 2021, entitled “Waste-Free Processing for Lignin Modification of Fibrous Plant Materials, and Lignin-Modified Fibrous Plant Materials,” which is incorporated by reference herein in its entirety.
This invention was made with government support under DEAR0001025 awarded by the U.S. Department of Energy, Advanced Research Projects Agency-Energy (ARPA-E). The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US22/41779 | 8/27/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63237625 | Aug 2021 | US |
