Strong and tough structural wood materials, and methods for fabricating and use thereof

Patent metadata

Field	Value
Publication number	US-2022040881-A1
Application number	US-202117408695-A
Country	US
Kind code	A1
Filing date	Aug 23, 2021
Priority date	Apr 10, 2017
Publication date	Feb 10, 2022
Grant date	—

Abstract

A super strong and tough densified wood structure is formed by subjecting a cellulose-based natural wood material to a chemical treatment that partially removes lignin therefrom. The treated wood retains lumina of the natural wood, with cellulose nanofibers of cell walls being aligned. The treated wood is then pressed in a direction crossing the direction in which the lumina extend, such that the lumina collapse and any residual fluid within the wood is removed. As a result, the cell walls become entangled and hydrogen bonds are formed between adjacent cellulose nanofibers, thereby improving the strength and toughness of the wood among other mechanical properties. By further modifying, manipulating, or machining the densified wood, it can be adapted to various applications.

First claim

1 - 132 . (canceled)

133 . A structure comprising:
a chemically-modified, densified piece of wood having a tensile strength of at least 350 MPa and a density of 1.13-1.30 g/cm 3 , wherein lumina, which were defined by a cellulose-based microstructure of the wood in its native state, are collapsed within the chemically-modified, densified piece of wood, and wherein lignin, which was present in the wood in its native state, is at least partially removed from the cellulose-based microstructure of the chemically-modified, densified piece of wood.

134 . The structure of claim 133 , wherein hydrogen bonds couple together facing portions of the collapsed lumina in the chemically-modified, densified piece of wood.

135 . The structure of claim 133 , wherein cellulose nanofibers within the chemically-modified, densified piece of wood are aligned substantially parallel to a direction of extension of the collapsed lumina.

136 . The structure of claim 133 , further comprising non-native hydrophobic nanoparticles incorporated within the collapsed lumina in the chemically-modified, densified piece of wood.

137 . The structure of claim 133 , further comprising a paint or coating on one or more external surfaces of the chemically-modified, densified piece of wood.

138 . The structure of claim 133 , wherein the chemically-modified, densified piece of wood retains at least 5% of the lignin present in the wood in its native state.

139 . The structure of claim 133 , wherein a lignin content of the chemically-modified, densified piece of wood is 5-16 wt%, inclusive.

140 . A method comprising:
chemically-modifying a piece of wood by immersing in a delignification solution such that lumina, which were defined by a cellulose-based microstructure of the wood in its native state and extend in a first direction, are substantially preserved; and pressing the piece of chemically-modified wood in a second direction crossing the first direction such that the preserved lumina collapse so as to form a chemically-modified, densified piece of wood having a tensile strength of at least 350 MPa and a density of 1.13-1.30 g/cm 3 .

141 . The method of claim 140 , wherein the chemically-modifying is effective to remove at least some of lignin, which was present in the wood in its native state, from the cellulose-based microstructure of the piece of wood.

142 . The method of claim 141 , wherein, after the chemically-modifying, the piece of wood retains at least 5% of the lignin present in the wood in its native state.

143 . The method of claim 141 , wherein, after the chemically-modifying, a lignin content of the piece of wood is 5-16 wt%, inclusive.

144 . The method of claim 140 , wherein the delignification solution comprises an alkaline solution.

145 . The method of claim 140 , wherein, after the pressing:
cellulose nanofibers within the chemically-modified, densified piece of wood are aligned substantially parallel to a direction of extension of the collapsed lumina; and hydrogen bonds couple together facing portions of the collapsed lumina in the chemically-modified, densified piece of wood.

146 . The method of claim 140 , further comprising, after the pressing, applying a coating or paint to one or more external surfaces of the chemically-modified, densified piece of wood.

147 . The method of claim 140 , further comprising:
prior to the pressing, depositing non-native hydrophobic nanoparticles within the lumina or over internal surfaces of the cellulose-based microstructure, wherein, after the pressing, the non-native hydrophobic nanoparticles are incorporated within the collapsed lumina.

148 . The method of claim 140 , further comprising:
after the chemically-modifying, further treating the piece of wood to improve resistance to weather or salt water by immersing in 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, kreosote, titanium dioxide, propiconazole, tebuconazole, cyproconazole, boric acid, borax, organic iodide (IPBC), Na 2 B 8 O 13 .4H 2 O, or any combination of the foregoing.

149 . The method of claim 140 , wherein a thickness of the chemically-modified, densified piece of wood after the pressing is at least 60% reduced as compared to a thickness of the piece of wood prior to the chemically-modifying.

150 . A method comprising:
providing a plurality of chemically-modified, densified pieces of wood, each having a tensile strength of at least 350 MPa and a density of 1.13-1.30 g/cm 3 ; and coupling together at least two of the chemically-modified, densified pieces of wood to form a wooden structure.

151 . The method of claim 150 , wherein the coupling comprises bonding together facing surfaces of adjacent chemically-modified, densified pieces to form a layered structure.

152 . The method of claim 150 , further comprising:
prior to or after the coupling, machining or manipulating one or more of the chemically-modified, densified pieces of wood to alter a structure or shape thereof, wherein the machining comprises cutting, drilling, woodturning, tapping, boring, carving, routing, sanding, grinding, abrasive tumbling, or any combination of the foregoing; and the manipulating comprises bending, molding, or both bending and molding.

Assignees

• Univ Maryland

Inventors

• Hu Liangbing
• Zhu Mingwei
• Song Jianwei

Classifications

• D21C9/007

  by mechanical or physical means · CPC title

• D21C9/005

  organic compounds · CPC title

• D21C3/12

  sodium bisulfite · CPC title

• D21C3/022

  in presence of S-containing compounds · CPC title

• D21C3/00

  Pulping cellulose-containing materials (digesters D21C7/00) · CPC title