Source: FOREST PRODUCTS LABORATORY submitted to
CELL WALL SCIENCE & TECHNOLOGY
Sponsoring Institution
Forest Service/USDA
Project Status
COMPLETE
Funding Source
USDA INHOUSE
Reporting Frequency
Annual
Accession No.
0419190
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2012
Project End Date
Sep 30, 2022
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Project Director
Frihart, C.
Recipient Organization
FOREST PRODUCTS LABORATORY
ONE GIFFORD PINCHOT DRIVE
MADISON,WI 53726
Performing Department
(N/A)
Non Technical Summary
Comprehend key chemical and structural aspects of the cell wall so that forest products utilization can be increased and improved for traditional and non-traditional uses. The overall goal is to establish a better understanding of the chemistry of the cell wall and how the cell wall polymers are spatially arranged with respect to each other at the molecular level, as well as the nanoscale level.
Animal Health Component
20%
Research Effort Categories
Basic
70%
Applied
20%
Developmental
10%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1230650200050%
1230650201035%
1230650202015%
Knowledge Area
123 - Management and Sustainability of Forest Resources;

Subject Of Investigation
0650 - Wood and wood products;

Field Of Science
2010 - Physics; 2020 - Engineering; 2000 - Chemistry;
Goals / Objectives
The focus of this problem is to bridge the fundamental understanding of wood cell wall chemistry, biology, and mechanics with novel and applied technologies involving wood cell walls. The fundamental aspects of the cell wall that we learn will be a foundation on which all developed technologies can be built upon. Aspects will include research surrounding cell wall ultrastructure and architecture on a micron-scale, nano-scale, and ÿngstrom-scale. The components of this area include: (1) characterizing cell wall polymers in native wood and modified wood; (2) establishing more accurate wood cell wall models; (3) understanding structure-property relationships via water/solvent/component inter-diffusion and infiltration in the matrix; (4) improving the cell wall properties (physical, mechanical, biological degradation, fire resistance, etc.); (5) utilizing cell wall polymers from trees and plants for bio-resins and bio-energy.
Project Methods
Widely varied.

Progress 10/01/12 to 09/30/22

Outputs
OUTPUTS: Newly developed tools, micro-synchrotron-based X-ray fluorescence microscopy (µXFM) and custom humidly chambers, were used to better understand the mechanisms of water and ion movement through the wood cell wall under different humidity conditions. This allowed the determination of the wood moisture level needed to plasticize the wood polymers enough to allow ion movement, which causes corrosion of metallic connections and wood decay. The moisture-related properties of wood are poorly understood. To address this, a variety of sophisticated techniques and an extensive literature evaluation were used to relate the moisture response of wood across many levels. These analyses investigated the problem and build connections between responses at scales of the molecule, elementary fibril, secondary cell wall nanostructure, cell wall, and cellular bundles. Despite the importance of cell wall diffusion to nearly all aspects of wood utilization, diffusion mechanisms and the detailed effects of moisture remain poorly understood. A polymer-science-based approach to wood was employed, assuming that wood polymers (cellulose, hemicelluloses, and lignin) behave like typical solid polymers. Through an extensive review and analysis of available literature, a comprehensive explanation of diffusion through the wood cell wall was presented, replacing historical models of cell wall structure with one consistent with our modern understanding of polymers. Understanding the natural decay mechanisms of wood by fungi has been important to reducing rot for wood products in service and to speed up wood deconstruction for value added chemicals. The process is far more complicated than first contemplated, with many overlapping chemical and enzymatic mechanisms. Now, the mechanism of the brown rot by Gloeophyllum trabeum has been elaborated by using specific enzymatic and chemical treatments on southern yellow pine, followed by examining the treated wood with small angle neutron scattering, which allowed separating lignin depolymerized from cellulose elementary fibril deconstruction at different stages of decay. Another program used fluorescently labelled proteins with specific binding properties to map the location of crystalline and noncrystalline cellulose in paper fibers at various stages of enzymatic digestion. This quantitative analysis, along with several other experiments, showed how a commercial enzyme mixture preferentially attacks noncrystalline cellulose and could be improved. To better understand the chemical reactions taking place during when wood burns, and therefore improve fire performance of wood products, X-ray photoelectron spectroscopy was used to examine the chemistry of Douglas fir exposed to flaming combustion. Lignin, though present in large quantities, is very difficult to analyze. A multifaceted approach for determining the absolute values for lignin subunits in lignocellulosic materials was developed. A key was to determine the absolute value of methoxyl groups and then to use other methods, such as gas chromatography, mass spectroscopy, and NMR spectroscopy for quantification of other components. PARTICIPANTS: Advanced Photon Source Argonne National Laboratory, Lemont, IL; Central South University of Forestry and Technology, Changsha, China; National Renewable Energy Laboratory, Golden, CO; The University of British Columbia, Vancouver, BC, Canada; Tokyo University of Agriculture and Technology, Fuchu, Japan; University of Massachusetts, Amherst, MA; University of Minnesota, Saint Paul, MN, University of Wisconsin, Madison, WI. TARGET AUDIENCES: This research will bring new fundamental knowledge on wood structure, behavior, and its modification that will drive applied research and development innovation. The main groups that will benefit are the forest products industry product development and improvement groups and other researchers in the field There is an implicit invitation for them to enter in to collaboration on future research, especially towards harnessing the new knowledge for new products and product technology. PROJECT MODIFICATIONS: This problem area is fundamental and will be continued in our Research Work Unit Description. We will be reviewing and revising our Research Work Unit Description in 2021.

Impacts
Research on this problem bridges the fundamental understanding of wood cell wall chemistry, biology, and mechanics through novel analytical techniques to applied technology research. The fundamental aspects of the cell wall are a foundation on which all developed technologies can be built upon. Specifically, this research significantly expands our knowledge of cell wall structure and how that structure drives product function. The applications include decay, fastener corrosion, wood dimensional stability, adhesion, composites, pulping, fire performance, etc.

Publications

  • Arzola-Villegas, Xavier; Lakes, Roderic; Plaza, Nayomi Z.; Jakes, Joseph E. 2019. Wood moisture-induced swelling at the cellular scale⿿Ab Intra. Forests. 10(11): 996. 19 p.
  • Hasburgh, Laura E.; Stone, Donald S.; Zelinka, Samuel L.; Plaza, Nayomi Z. 2020. Characterization of wood chemical changes caused by pyrolysis during flaming combustion using x-ray photoelectron spectroscopy. Wood & Fire Safety, 2020. 22-27.
  • Jakes, Joseph E.; Frihart, Charles R.; Hunt, Christopher G.; Yelle, Daniel J.; Plaza, Nayomi Z.; Lorenz, Linda F.; Ching, Daniel J. 2018. Integrating multiscale studies of adhesive penetration into wood. Forest Products Journal. 68(4): 340-348.
  • Jakes, Joseph E.; Hunt, Christopher G.; Zelinka, Samuel L.; Ciesielski, Peter N.; Plaza, Nayomi Z. 2019. Effects of moisture on diffusion in unmodified wood cell walls: a phenomenological polymer science approach. Forests. 10(12): 1084. https://doi.org/10.3390/f10121084.
  • Jakes, Joseph E.; Zelinka, Samuel L.; Hunt, Christopher G.; Ciesielski, Peter; Frihart, Charles R.; Yelle, Daniel; Passarini, Leandro; Gleber, Sophie-Charlotte; Vine, David; Vogt, Stefan. 2020. Measurement of moisture-dependent ion diffusion constants in wood cell wall layers using time-lapse micro X-ray fluorescence microscopy. Scientific Reports. 10(1): 484. 15 p.
  • Novy, Vera; Aïssa, Kevin; Nielsen, Fredrik; Straus, Suzana K.; Ciesielski, Peter; Hunt, Christopher G.; Saddler, Jack. 2019. Quantifying cellulose accessibility during enzyme-mediated deconstruction using 2 fluorescence-tagged carbohydrate-binding modules. Proceedings of the National Academy of Sciences. 116(45): 22545-22551.
  • Yelle, Daniel J. 2020. Multifaceted approach for determining the absolute values for lignin subunits in lignocellulosic materials. Res. Note. FPL-RN-0384. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 7 p.
  • Zhu, Yuan; Plaza, Nayomi; Kojima, Yuka; Yoshida, Makoto; Zhang, Jiwei; Jellison, Jody; Pingali, Sai Venkatesh; O⿿Neill, Hugh; Goodell, Barry. 2020. Nanostructural analysis of enzymatic and non-enzymatic brown rot fungal deconstruction of the lignocellulose cell wall. Frontiers in Microbiology. 11: 1389.


Progress 10/01/12 to 09/30/19

Outputs
OUTPUTS: X-ray fluorescence microscopy paired with an in situ humidity chamber was used to observe the transport of an implanted model metabolite, potassium (K+) ions, in wood cell walls as a function of relative humidity (RH) and extent of the wood acetylation. This revealed that deuterium-labelled phenol formaldehyde (dPF) adhesive infiltrated all the way into the water-accessible regions between the elementary fibrils within the wood cell walls. These results provide new insight that adhesive infiltration into the cellulose microfibril (a bundle of elementary fibrils) may be a key to designing moisture-durable wood adhesives. Modification of southern pine with epoxybutene (EpB) and subsequent decay evaluations found that biological resistance correlated with the lowering of the equilibrium moisture content, suggesting that the cause was moisture exclusion. X-ray scattering revealed that the modification may target regions outside the microfibrils. Nanomechanical spectroscopy was used to measure changes in moisture-dependent relaxations of amorphous polysaccharides inside loblolly pine (Pinus taeda) cell wall layers. This revealed that mineral ion diffusion occurs via interconnecting nanoscale pathways of rubbery amorphous polysaccharides. This result contradicts previous assertions of cell wall transport being an aqueous process occurring through simple interconnecting water pathways. The identification of the diffusion mechanism in this manuscript opens up a new paradigm in lignocellulosic research. Reviews were written that highlighted questions that still need to be addressed on molecular-scale wood-water interactions needed for moisture-durability, and fundamentals of wood bonding and developments in the analyses and understanding of wood bonds. Synchrotron based X-ray fluorescence microscopy and X-ray absorption near edge spectroscopy were harnessed to examine the corrosion mechanism of fasteners in treated wood by looking at the spatial distribution and oxidation states of copper in the treated wood near the fastener and in the corrosion products removed from the fastener surface. Together, these techniques confirm that the corrosion mechanism involves transport of the cupric ions to the fastener surface, where they are reduced and suggest that previous attempts to detect copper were unsuccessful because the concentration of copper in the corrosion products was below the level of detection of the previously used techniques. PARTICIPANTS: Kronospan GmbH, Lampertswalde, Germany, FibreLaboratory, South-Eastern Finland University of Applied Sciences, Savonlinna, Finland, Argonne National Laboratory, Advanced Photon Source, Lemont, IL, Institute for X-ray Physics, Georg-August Universität, Göttingen, Germany, Collège Communautaire du Nouveau-Brunswick, Campbellton, Canada, School of Forest Resources and Advanced Structures and Composites Center, University of Maine, Orono, ME, Ecovative Design, LLC., Cohoes Avenue, Green Island, NY, William T. Heller & Sai Venkatesh Pingali, Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, Department of Bioproducts and Biosystems, School of Chemical Engineering, and Department of Applied Physics, School of Science, Aalto University, Espoo, Finland, RWU 4716 TARGET AUDIENCES: This research will bring new fundamental knowledge on wood structure, behavior, and its modification that will drive applied research and development innovation. The main groups that will benefit are the forest products industry product development and improvement groups and other researchers in the field There is an implicit invitation for them to enter in to collaboration on future research especially towards harnessing the new knowledge for new products and product technology.

Impacts
Research on this problem bridges the fundamental understanding of wood cell wall chemistry, biology, and mechanics with novel and applied technologies involving wood cell walls. The fundamental aspects of the cell wall are a foundation on which all developed technologies can be built upon. Specifically, this research significantly expands our knowledge of cell wall structure, function, etc. and the interrelation with applications such as adhesion, composites, decay, etc.

Publications

  • Hunt, Christopher G.; Frihart, Charles R.; Dunky, Manfred; Rohumaa, Anti. 2018. Understanding wood bonds⿿going beyond what meets the eye: a critical review. Reviews of Adhesion and Adhesives. 6(4): 369-440.
  • Hunt, Christopher G.; Zelinka, Samuel L.; Frihart, Charles R.; Lorenz, Linda; Yelle, Daniel; Gleber, Sophie-Charlotte; Vogt, Stefan; Jakes, Joseph E. 2018. Acetylation increases relative humidity threshold for ion transport in wood cell walls ⿿ a means to understanding decay resistance. International Biodeterioration & Biodegradation. 133: 230-237.
  • Ibach, Rebecca E.; Plaza, Nayomi. 2019. Using x-ray scattering to elucidate the mechanisms behind the moisture and fungal decay resistance of epoxybutene modified wood. In: Proceedings, 2019 IRG annual meeting. Stockholm, Sweden: The International Research Group on Wood Protection. 15 p.
  • Jakes, Joseph E. 2019. Mechanism for diffusion through secondary cell walls in lignocellulosic biomass. The Journal of Physical Chemistry B. 123(19): 4333-4339.
  • Plaza, Nayomi Z. 2019. On the experimental assessment of the molecular-scale interactions between wood and water. Forests. 10(8). 12 p.
  • Plaza, Nayomi Z.; Jakes, Joseph E.; Frihart, Charles R.; Hunt, Christopher G.; Yelle, Daniel J.; Lorenz, Linda F.; Heller, William T.; Pingali, Sai Venkatesh; Stone, Donald S. 2017. Small-angle neutron scattering as a new tool to evaluate moisture-induced swelling in the nanostructure of chemically modified wood cell walls. Forest Products Journal. 68(4): 349-352.
  • Zelinka, Samuel L.; Jakes, Joseph E.; Kirker, Grant T.; Passarini, Leandro; Hunt, Christopher G.; Lai, Barry; Antipova, Olga; Li, Luxi; Vogt, Stefan. 2019. Copper distribution and oxidation states near corroded fasteners in treated wood. SN Applied Sciences. 1(3): 1-10.


Progress 10/01/12 to 09/30/17

Outputs
OUTPUTS: Characterize wood cell wall polymers: We demonstrated that extracellular expression of ferritin in Arabidopsis can produce plants with increased growth and iron accumulation, and reduced thermal and enzymatic recalcitrance. The results are attributed to the intimate colocation of the iron co-catalyst and the cellulose and hemicellulose within the plant cell-wall region. XANES was used as a complimentary technique to differentiate between oxidation states of copper in the wood. The data suggest a large fraction of the copper is in a copper (I) oxidation state. To simulate fuel oil spills occurring during catastrophic floods, short-term absorption of two chemicals, n-hexadecane (representative of semivolatile organic compounds in fuel oil) and water, into southern yellow pine was gravimetrically monitored as a function of time at ambient conditions. Presaturation of wood with water did not significantly impede the subsequent penetration of n-hexadecane, whereas the presaturation of wood with n-hexadecane led to a significant decrease of the subsequent water uptake. In this research, a dilute solution of hydroxymethylated resorcinol (HMR) is cured in the presence of a crude milled-wood lignin (cMWL) from Acer saccharum and subsequently dissolved in dimethylsulfoxide-d6 to delineate reactivity with lignin and O-acetyl-(4-O-methylglucurono) xylan using solution-state NMR spectroscopy. No evidence of reactivity between HMR and lignin subunits was found. Ipê is an extremely difficult species to bond because of its high density, interlocking grain, and high volumetric swelling⿿shrinkage under prolonged wet conditions. ipê wood was bonded and discovered that phenol-resorcinol formaldehyde provided the most durable bonds and highest wood failure after cyclic vacuum pressure soaking. Transmitted-light microscopy showed that phenol-resorcinol formaldehyde traveled between surface fiber cells more effectively than did other adhesives. New wood cell wall models: We employed synchrotron-based X-ray fluorescence microscopy (XFM) to map and quantify physiologically relevant ions, such as K, Ca, Mn, Fe, and Zn, in wood being decayed by the model brown rot fungus Serpula lacrymans. Results show that the fungus actively transports some ions, such as Fe, into the wood and controls the distribution of ions at both the bulk wood and cell wall length scales. The crinkle-leaf mutant has the potential to be a useful model system for wood properties investigation and manipulation if it can serve as a field-observable vegetative marker for altered wood properties. A combination of experimental, theoretical and numerical studies is used to investigate the variation of elastic moduli of lignocellulosic (bamboo) fiber cell walls with moisture content (MC). Our Nanoindentation results show that the longitudinal elastic modulus initially increased to a maximum value at about 3% MC and then decreased linearly with increasing MC. In contrast, the transverse moduli decrease linearly with MC.

Impacts
Research on this problem bridges the fundamental understanding of wood cell wall chemistry, biology, and mechanics with novel and applied technologies involving wood cell walls. The fundamental aspects of the cell wall are foundation on which all developed technologies can be built upon. Specifically, this research significantly expands our knowledge of cell wall structure, function, etc. and the interrelation with applications such as adhesion, composites, decay, etc.

Publications

  • Lin, Chien-Yuan; Jakes, Joseph E.; Donohoe, Bryon S.; Ciesielski, Peter N.; Yang, Haibing; Gleber, Sophie-Charlotte; Vogt, Stefan; Ding, Shi-You; Peer, Wendy A.; Murphy, Angus S.; McCann, Maureen C.; Himmel, Michael E.; Tucker, Melvin P.; Wei, Hui. 2016. Directed plant cell-wall accumulation of iron: embedding co-catalyst for efficient biomass conversion. Biotechnology for Biofuels. 9(1): 804-819.
  • Wiedenhoeft, Alex C.; Arévalo, Rafael; Ledbetter, Craig; Jakes, Joseph E. 2016. Structure⿿property characterization of the crinkle-leaf peach wood phenotype: a future model system for wood properties research? Journal of the Mineral Metals and Materials. 68(9): 2405-2412.
  • Yelle, Daniel J. 2016. Bondability of ipê (Tabebuia spp.) wood using ambient-curing exterior wood adhesives. FPL⿿RP⿿689. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 6 p.
  • Yelle, Daniel J. 2017. Solution-state NMR analysis of hydroxymethylated resorcinol cured in the presence of crude milled-wood lignin from Acer saccharum . Journal of Applied Polymer Science. 134(41): 1-9.
  • Youssefian, S.; Jakes, J. E.; Rahbar, N. 2017.Variation of nanostructures, molecular interactions, and anisotropic elastic moduli of lignocellulosic cell walls with moisture. Nature Scientific Reports. 7(2054): 1-10 pp.
  • Baglayeva, Ganna; Seames, Wayne S.; Frihart, Charles R.; O'Dell, Jane; Kozliak, Evguenii I. 2017. Penetration of n-hexadecane and water into wood under conditions simulating catastrophic floods. Forest Products Journal. 67(3/4): 236-244.
  • Chen, Liheng; Dou, Jinze; Ma, Qianli; Li, Ning; Wu, Ruchun; Bian, Huiyang; Yelle, Daniel J.; Vuorinen, Tapani; Fu, Shiyu; Pan, Xuejun; Zhu, Junyong (J.Y.) 2017. Rapid and near-complete dissolution of wood lignin at ⿤80°C by a recyclable acid hydrotrope. Science Advances. 3: 1-11.
  • Hunt, Christopher G.; Jakes, Joseph; Frihart, Charles. 2017. Advanced analysis tools and programs to accelerate the adoption of more natural structures. In: Proceedings, COST action FP1407 - 3rd conference, Wood modification research and applications. Kuchl, Austria: Salzburg University of Applied Sciences. p. 19-20.
  • Kirker, Grant; Zelinka, Sam; Gleber, Sophie-Charlotte; Vine, David; Finney, Lydia; Chen, Si; Hong, Young Pyo; Uyarte, Omar; Vogt, Stefan; Jellison, Jody; Goodell, Barry; Jakes, Joseph E. 2017. Synchrotron-based X-ray fluorescence microscopy enables multiscale spatial visualization of ions involved in fungal lignocellulose deconstruction. Scientific Reportsl. 7:41798. pp. 1-15.
  • Zelinka, Samuel L.; Kirker, Grant T.; Jakes, Joseph E.; Passarini, Leandro; Lai, Barryl. 2016. Distribution and oxidation state of copper in the cell walls of treated wood examined by synchrotron based XANES and XFM. In: Proceedings of CORROSION 2017. American Wood Protection Association: 172-178.


Progress 10/01/15 to 09/30/16

Outputs
OUTPUTS: Characterize wood cell wall polymers: We grew Phanerochaete chrysosporium on solid spruce wood and included oxidant-sensing beads bearing the fluorometric dye BODIPY 581/591 in the cultures. Confocal fluorescence microscopy of the beads showed that extracellular oxidation commenced 2 to 3 days after inoculation, coincident with cessation of fungal growth. Whole transcriptome shotgun sequencing (RNA-seq) analyses based on the v.2.2 P. chrysosporium genome identified genes at various stages of decay. Adhesive bonding of wood using phenol-formaldehyde remains the industrial standard in wood product bond durability. Our results provide evidence for a simultaneous wood polymer degradation and guaiacyl unit C5 bond that occurs during phenol-formaldehyde curing. This competition may be necessary for developing good bond durability between the adhesive and wood. New wood cell wall models: Recent work has highlighted the importance of movement of chemicals and ions through the wood cell wall. This movement depends strongly on moisture content and is necessary for structural damage mechanisms such as fastener corrosion and wood decay. The first measurements of electrical resistance of southern pine at the subcellular level as a function of wood moisture content by using a 1-um-diameter probe. The fiber saturation point (FSP) is an important concept in wood⿿ moisture relations that differentiates between the states of water in wood and has been discussed in the literature for over 100 years. Despite its importance and extensive study, the exact theoretical definition of the FSP and the operational definition are still debated because different methods give a wide range of values. A theoretical definition of the FSP has been developed based on solution thermodynamics that treats the FSP as a phase boundary. This thermodynamic interpretation allows FSP to be calculated from the chemical potentials of bound and free water as a function of moisture content, assuming that they are both known. Synchrotron based XANES and XFM were used to examine the role of copper in the corrosion of metals in treated wood. The spatial distribution of the concentration of copper in wood that had been next to corroding fasteners was mapped using XFM. The oxidation state of the copper in the wood immediately next to the fastener and farther away from the fastener was measured using XANES. These combined methods revealed a zone near the fastener where there is a much lower concentration of copper. This zone roughly corresponds with the distance that the iron corrosion products have diffused into the wood. Small angle neutron scattering (SANS) from intact wood sections cut from each primary wood orientation showed that although wood scattered anisotropically across 1.3⿿600 nm length scales, measurement of elementary fibril spacing and low-q surface scattering were independent of orientation. Water sorption caused spacing between elementary fibrils to increase with RH, and this swelling accounted for over half the transverse swelling in S2 secondary wood cell walls.

Impacts
Research on this problem bridges the fundamental understanding of wood cell wall chemistry, biology, and mechanics with novel and applied technologies involving wood cell walls. The fundamental aspects of the cell wall are foundation on which all developed technologies can be built upon. Specifically, this research significantly expands our knowledge of cell wall structure, function, etc. and the interrelation with applications such as adhesion, composites, decay, etc.

Publications

  • Chen, Yao; Stark, Nicole M.; Tshabalala, Mandla A.; Gao, Jianmin; Fan, Yongming. 2016. Weathering characteristics of wood plastic composites reinforced with extracted or delignified wood flour. Materials. 9(610). DOI: 10.3390/ma9080610. 12 pp.
  • Houtman, Carl J.; Kitin, Peter; Houtman, Jon C. D.; Hammel, Kenneth E.; Hunt, Christopher G. 2016. Acridine orange indicates early oxidation of wood cell walls by fungi. PLOS ONE. 11(7). DOI: 10.1371/journal.pone.0159715 19 p.
  • Korripally, Premsagar; Hunt, Christopher G.; Houtman, Carl J.; Jones, Don C.; Kitin, Peter J.; Cullen, Dan; Hammel, Kenneth E. 2015. Regulation of gene expression during the onset of ligninolytic oxidation by Phanerochaete chrysosporium on spruce wood. Applied and Environmental Microbiology. 81(22): 7802-7812.
  • Plaza, Nayomi Z.; Pingali, Sai Venkatesh; Qian, Shuo; Heller, William T.; Jakes, Joseph E. 2016. Informing the improvement of forest products durability using small angle neutron scattering. Cellulose. 23: 1593-1607.
  • Stark, Nicole M.; Yelle, Daniel J.; Agarwal, Umesh P. 2016. Techniques for characterizing lignin. In: Lignin in Polymer Composites. Faruk, Omar; Sain, Mohini, eds. Elsevier; Kidlington, Oxford. Chapter 4: 49-66.
  • Yelle, Daniel J.; Ralph, John. 2016. Characterizing phenol-formaldehyde adhesive cure chemistry within the wood cell wall. International Journal of Adhesion and Adhesives. 70: 26-36.
  • Yelle, Daniel J.; Ralph, John. 2016. Phenol-formaldehyde reactivity with lignin in the wood cell wall. In: Proceedings of the International Conference on Polyphenols; Krebs, Heinz A., Ed. 11-15 July 2016. Vienna, Austria. Ed.: Publisher: Book-of-Abstracts.com. pp. 170-171.
  • Yelle, Daniel J.; Ralph, John. 2016. Simultaneous bond degradation and bond formation during phenol-formaldehyde curing with wood. In: WTCE 2016, World Conference on Timber Engineering; 22-25 August . Vienna, Austria. 7 pp.
  • Zelinka, Samuel L.; Glass, Samuel V.; Jakes, Joseph E.; Stone, Donald S. 2016. A solution thermodynamics definition of the fiber saturation point and the derivation of a wood-water phase (state) diagram. Wood Science and Technology. 50: 443-462.
  • Zelinka, Samuel L.; Jakes, Joseph E.; Kirker, Grant T.; Passarini, Leandro; Lai, Barry. 2016. Corrosion of metals in treated wood examined by synchrotron based XANES and XFM. NACE International, Corrosion 2016 Conference and Expo. Paper No. 7038. 10 pp.
  • Zelinka, Samuel L.; Passarini, Leandro; Colon Quintana, José L.; Glass, Samuel V.; Jakes, Joseph E.; Wiedenhoeft, Alex C. 2016. Cell wall domain and moisture content influence southern pine electrical conductivity. Wood and Fiber Science. 48: 54-61.


Progress 10/01/14 to 09/30/15

Outputs
OUTPUTS: New wood cell wall models: Research on the free diffusion of ions through wood secondary walls and middle lamellae was carried out as a function of moisture content (MC) and anatomical direction. The observations from this research support a recently proposed percolation model of electrical conduction in wood. The results contribute to understanding the mechanisms of fungal decay and fastener corrosion that occur below the fiber saturation point. The transport mechanism proposed by Jakes et al. depends upon a moisture induced glass transition occurring in the hemicelluloses. Research studied the predicted dependencies. It was found that ion transport resistance decreased with increasing relative humidity in all locations. The resistance decreased more rapidly with relative humidity in the S2 layer than in the middle lamella. Structure-property relationships via inter-diffusion and infiltration in the cell wall matrix: Although it is well known that wood can absorb liquids, the full impact of this phenomenon on resulting adhesive cure and performance is not well understood. This research supports the concept that wood acts as a polar-size exclusion chromatography medium, removing LMW components from the liquid adhesive around it. As a consequence, adhesives cured neat can be chemically, morphologically, and mechanically different from adhesives cured in contact with wood. In plywood production, human operators find it difficult to precisely monitor the spread rate of adhesive in real-time. Research was directed at this problem via macroscopic fluorescence to estimate spread rate (SR) of urea formaldehyde adhesive on birch (Betula pendula Roth) veneer. The results allowed visualization of spread and penetration rates. The weathering performance of wood coated with a combination of rutile TiO2 hierarchical nanostructures and a sol-gel deposit of alkoxysilanes was determined by exposing three sets of specimens to UV light and water spray. Superior photostabilization properties and resistance to surface erosion found in these materails may be useful for improving the weathering performance of wood coated with semi-transparent wood stains. Bioresins and bioenergy: Research was directed at investigating the potential for using purified CO2-precipitated Kraft lignin (PCO2KL) with phenol-formaldehyde (PF) for application as an adhesive in plywood production Formulated adhesives were compared to a control phenol-formaldehyde (PF) adhesive prepared in the laboratory. PCO2KL-based adhesives showed comparatively good plywood shear strengths. However, they had lower fractional wood substrate failures than those of test samples made from PF resin only.

Impacts
This research improved our understanding of the wood cell wall 3D structure down to the nanoscale and how materials applied to the cell wall interact with it. The research in this problem area contributes to understanding the mechanisms of fungal decay and fastener corrosion that occur below the fiber saturation point, understanding how some moisture-dependent wood properties affect ion movement may be partitioned across cell wall layers, informing industry on how adhesives cured neat can be chemically, morphologically, and mechanically different from adhesives cured in contact with wood, and provide new materials approaches to enhanced weathering resistance of semi-transparent wood stains.

Publications

  • Antikainen, Toni; Rohumaa, Anti; Hunt, Christopher G.; Levirinne, Mari; Hughes, Mark 2015. Estimating the spread rate of urea formaldehyde adhesive on birch (Betula pendula Roth) veneer using fluorescence. Eur. J. Wood Prod. Volume 73, 2015; pp. 69⿿75.
  • Chen, Yao; Frihart, Charles R.; Cai, Zhiyong; Lorenz, Linda F.; Stark, Nicole M. 2013. Lignin-based Phenol-Formalehyde Resins from Purified CO2 Precipitated Kraft Lignin (PCO2KL). In: International Conference on Wood Adhesives, 2013; pp. 601-610.
  • Hunt, Christopher; O'Dell, Jane; Jakes, Joseph; Grigsby, Warren J.; Frihart, Charles R. 2015. Wood as Polar Size Exclusion Chromatography Media: Implications to Adhesive Performance. Forest Prod. J. Volume 65, Number 1/2, 2015; pp. 9⿿14.
  • Zelinka, Samuel L.; Gleber, Sophie-Charlotte; Vogt, Stefan; Rodriguez Lopez, Gabriela M.; Jakes, Joseph E. 2015. Threshold for ion movements in wood cell walls below fiber saturation observed by X-ray fluorescence microscopy (XFM). Holzforschung. 69(4), pp. 441-448.
  • Zelinka, Samuel L.; Quintana, José L. Colon; Glass, Samuel V.; Jakes, Joseph E.; Wiedenhoeft, Alex C. 2015. Subcellular Electrical Measurements as a Function of Wood Moisture Content. Proceedings of the 58th International Convention of Society of Wood Science and Technology, June 7-12, 2015 ⿿ Grand Teton National Park, Jackson, Wyoming, USA. pp. 568-576.
  • Zheng, Rongbo; Tshabalala, Mandla A.; Li, Qingyu; Wang, Hongyan 2015. Weathering Performance of Wood Coated with a Combination of Alkoxysilanes and Rutile TiO2 Heirarchical Nanostructures. BioResources Volume 10, Number 4, 2015; pp. 7053-7064.


Progress 10/01/13 to 09/30/14

Outputs
OUTPUTS: Characterize wood cell wall polymers: To understand the effect of wood fiber on the performance properties and aesthetic qualities of wood plastic composites, wood flour was extracted with various solvents and also delignified, and its surface chemistry and color characterized. Results of this first of its kind study showed that lignin removal exerted the greatest influence on the surface chemistry of wood flour. The purpose of this study was to characterize the chemical transformations of lignin in woody tissues after anaerobic bacterial decomposition. This study found that lignin associations with structural carbohydrates were retained after decomposition. For hardwood and old newsprint, the carbon losses were attributed to losses in cellulose and hemicelluloses, while carbon loss in softwood was attributed to losses of the extractives. The white rot basidiomycete Ceriporiopsis subvermispora degrades spruce via selective lignin removal. This suggests that small diffusible oxidants contribute to delignification. A key question is whether these unidentified oxidants attack lignin via single electron transfer (SET). The results showed that (a) benzoic acid residues were the major identifiable truncated structures in the lignin after decay, and (b) depletion of β-aryl ether units was diastereoselective with a threo preference. The structural compliance method, which was previously developed at FPL to account for edge effects and specimen-scale flexing during nanoindentation of wood cell walls, has been shown to also be necessary to accurately assess mechanical properties of ceramic bone scaffolds. New wood cell wall models: A holistic wood adhesion model was expanded to include the need for repair of real wood surfaces. This examination of repair mechanisms supports the concept of two different adhesive classes operating by different modes in trying to repair the damage to the wood surface. This model is being used by other researchers in field. A book chapter was published that discusses what is known about soy protein structure and theories on why the protein in soy flour is not as effective in forming durable bonds as that in the commercial soy protein isolate. A new model was developed and presented which provides a physical model to explain the switch on/switch off movement of ions through cell walls. Because ion movement is a necessary condition for corrosion of fasteners and decay, stopping ion movement is a way to stop decay and corrosion in wood. In addition to purely fundamental understanding of how wood behaves, this new model includes a testable parameter (ion mobility) that should correlate with decay and corrosion resistance. Structure-property relationships via inter-diffusion and infiltration in the cell wall matrix: Thin silvers of wood were found to twist multiple revolutions with changes in moisture content. The slivers produce higher specific torque than current synthetic microtorsional actuators. Additionally, the wood slivers have a shape memory twist effect that along with ionic diffusion thresholds are believed to be controlled by a glass transition in the hemicelluloses. Small molecules do not appear to harm wood adhesive performance. Soy adhesives were made with labelled glycerin and the used to glue wood. The stiffness and concentration of labelled glycerin was measured in cells immediately adjacent the bondline showing that the small molecules had moved into the wood cell walls, slightly softening the wood. More importantly, their movement out of the adhesive improves the overall adhesive and product performance. Bioresins and bioenergy: This research analyzed lignin from loblolly pine, wheat straw, and miscanthus, following an ionic liquid pretreatment. The subsequent use of enzymes to breakdown the polysaccharides into simple sugars is thus more effective. Also, the size of the lignin polymer can be customized and routed into different product streams to improve biorefinery econo

Impacts
Evidence for diffusion of small chemicals from adhesives was shown to be a general phenomenon and in some cases to soften the wood substrate while stiffening the adhesive. The resulting changes in mechanical properties of both the cell and adhesive influence the mechanics and possibly the failure mechanisms of the finished products. The chemical movement into wood also explains a paradox in the performance of bio-based adhesives and provides a possible method of improving them. Wood slivers provide a new way to study moisture-induced swelling in wood. Because the slivers are thin, they can be extracted directly from wood adhesive bondlines and it is now possible to study the effects of adhesive infiltration on the moisture-induced swelling properties of cells infiltrated with adhesive. We have also hypothesized that the onset of fungal degradation in wood is related to the onset of ionic diffusion in wood cell walls. If true, then wood preservation treatments could be developed to prevent the hemicelluloses�� glass transition and ionic diffusion instead of relying on toxic biocided. Understanding and predicting ion mobility in wood not only provides a mechanism to explain basic behavior, it will allow much faster screening of nontoxic wood treatments for effectiveness in preventing wood decay and fastener corrosion. The demonstrated generality of the structural compliance method to new types of material systems further validates the method⿿s utility and accuracy. The work also improves FPL⿿s stature in the nanomechanics research community. A fundamental understanding of the role of wood flour surface chemistry is important in the manufacture of wood plastic composites that have superior performance properties and aesthetic qualities. If lignin in its native state was only exposed to an anaerobic environment, such as the deep layer of soil and marine sediments, the result would be a significant amount of recalcitrant carbon storage from plant biomass. Furthermore, the varying reactivity of different plant tissues has implications on the estimates of life cycle emissions of forest products where wood and similar tissues are treated as having the same decomposition rates under current greenhouse gas reporting protocols. The ligninolytic oxidants of the white rot fungus C. subvermispora are more diastereoselective than currently known fungal ligninolytic oxidants. This suggests that SET oxidation is one of the chemical mechanisms involved. Although identification of these selective agents will be a difficult challenge, once identified would have potential biotechnological applications, such as pretreating biomass to facilitate lignin removal. Using lignocellulosic biomass as renewable, plentiful, non-food and non-petroleum resources can help reduce dependence on oil products by supplementing traditional gasoline supplies with liquid biofuels. One of the biggest challenges of converting woody biomass to the sugars needed for biofuels is the nature of lignin itself; lignin does not break down easily. This research has the potential to unlock the resistant nature of lignin for the benefits of advanced biofuels. New knowledge disseminated on soy protein structure and theories on why the protein in soy flour is not as effective in forming durable bonds as that in the commercial soy protein isolate. Information is provided as to why some theories seem less valid on the basis of available data. The soy flour adhesives not only alleviate the concern over formaldehyde emissions, they also increase the biobased content of wood products; thus, understanding how to make them more effective is very important to the wood products industry. This work has been carried out with industry collaboration.

Publications

  • Chen, Yao; Stark, Nicole M.; Tshabalala, Mandla A.; Gao, Jianmin; Fan, Yongming 2014. Moisture Performance of wood-plastic composites reinforced with extracted and delignified wood flour. In: the ANTEC 2014, The Plastics Conference, April 28-30, 2014 Rio All-Suite Holtel & Casino, Las Vegas, Nevada; SPE ANTEC 2014 pp. 2049-2053.
  • Chen, Yao; Tshabalala, Mandla A.; Gao, Jianmin; Stark, Nicole M.; Fan Yongming 2013. Color and surface chemistry changes of extracted wood flour after heating at 120 °C. Wood Sci Technol Volume, 48 2014; pp. 137-150.
  • Chen, Yao; Tshabalala, Mandla A.; Gao, Jianmin; Stark, Nicole M.; Fan, Yongming 2014. Color and Surface Chemistry Changes of Pine Wood Flour after Extraction and Delignification. BioResources, Volume 9, Number 2, 2014; pp. 2937-2948.
  • Chen, Yao; Tshabalala, Mandla A.; Gao, Jianmin; Stark, Nicole M.; Fan, Yongming; Ibach, Rebecca E. 2014. Thermal behavior of extracted and delignified pine wood flour. Thermochimica Acta Volume 591, 2014; pp. 40⿿44.
  • Cruz, Florentino B. De la; Yelle, Daniel J.; Gracz, Hanna S.; Barlaz, Morton A. 2014. Chemical Changes during Anaerobic Decomposition of Hardwood, Softwood, and Old Newsprint under Mesophilic and Thermophilic Conditions. J. Agric. Food Chem. Volume 62, 2014; pp. 6362-6374.
  • Frihart, Charles R. 2013. How wood adhesives work and where are the areas for improvement. In: International Conference on Wood Adhesives 2013. Toronto, Ontario, Canada. October 9-11, 2013 from CD ISBN: 978-0-935018-37-0. 2013; pp. 50-63.
  • Frihart, Charles R. 2014. Many Roles of Wood Adhesives. In: The Adhesion society's 37th Annual Meeting, February 23-26, 2014. San Diego, CA, from CD TEH801043052B03; 2014; 4 p.
  • Frihart, Charles R.; Hunt, Christopher G.; Birkeland, Michael J. 2014. Chapter 16: Soy Proteins as Wood Adhesives. In: Recent Advances in Adhesion Science and Technology, edited by Woiciech (Voytek) Gutowski, and Hanna Dodiuk. 2014; pp. 277-290.
  • Jakes, Joseph E.; Plaza, Nayomi; Zelinka, Samuel L.; Stone, Donald S.; Gleber, Sophie-Charlotte; Vogt, Stefan 2014. Wood as inspiration for new stimuli-responsive structures and materials. Proceedings of SPIE Volume 9055, 90550K 2014 SPIE. 13 p.
  • Sathitsuksanoh, Noppadon; Holtman, Kevin M.; Yelle, Daniel J.; Morgan, Trevor; Stavila, Vitalie; Pelton, Jeffrey; Blanch, Harvey; Simmons, Blake A.; George, Anthe 2014. Lignin fate and characterization during ionic liquid biomass pretreatment for renewable chemicals and fuels production. Green Chem., Volume 16, 2014; pp. 1236⿿1247.
  • Hunt, Christopher G.; O'Dell, Jane; Jakes, Joseph; Grigsby, Warren; Frihart, Charles R. 2014. Wood as Polar Size Exclusion Chromatography Media: Implications to Adhesive Performance. Hunt, C. G., J. O⿿Dell, et al. (2014). "Wood as Polar Size Exclusion Chromatography Media: Implications to Adhesives" In proceedings of the International Conference on Wood Adhesives 2013 Toronto, Canada C. Hunt, C. Frihart and N. Yan. eds. Forest Products Society 2014; pp. 455-463.
  • Jakes, Joseph E.; Plaza, Nayomi; Stone, Donald S.; Hunt, Christopher G.; Glass, Samuel V.; Zelinka, Samuel L. 2013. Mechanism of Transport Through Wood Cell Wall Polymers. JOURNAL OF FOREST PRODUCTS & INDUSTRIES, Volume 2, Number 6, 2013; pp. 10-13.
  • Vivanco, Juan; Jakes, Joseph E.; Slane, Josh; Ploeg, Heidi-Lynn 2014. Accounting for structural compliance in nanoindentation measurements of bioceramic bone scaffolds. Ceramics International, 40+, 2014; pp. 12485-12492.
  • Yelle, Daniel J.; Kapich, Alexander N.; Houtman, Carl J.; Lu, Fachuang; Timokhin, Vitaliy I.; Fort Jr., Raymond C.; Ralph, John; Hammel, Kenneth E. 2014. A highly diastereoselective oxidant contributes to ligninolysis by the white rot basidiomycete Ceriporiopsis subvermispora . Appl. Environ. Microbiol. 2014; 31 p.


Progress 10/01/12 to 09/30/13

Outputs
OUTPUTS: Characterization of wood cell wall polymers in the native-state and modified states: Atomic Force Microscopy (AFM) and infrared (IR) spectroscopy have been combined in a single instrument capable of producing 100 nm spatial resolution IR spectra and images. This new capability enables the spectroscopic characterization of biomaterial domains at levels not previously possible. Differences in the IR spectra as a function of spatial position provide insight into microdomain formation and lead to increased understanding of how nanomaterial additives affect the molecular structure and properties of biomaterials. Research was conducted to study the effect of extractives and lignin on the thermal stability of wood flour (WF). Lignin was found to make a greater contribution to the thermal stability of WF than the extractives. In addition to research activities 3 book chapter review wood adhesives was authored and published. Establish new wood cell wall models through studies that challenge current theories or hypotheses on the cell wall architecture. Research revealed that a bundle of a few loblolly pine (Pinus taeda) cells can act as moisture-activated torsional actuator. The bundles generate greater specific torque than an electric motor. The bundles also exhibit shape memory behavior by recovering 70% of the set twist upon rewetting a dry and twisted bundle. Advances in understanding cell wall structure-property relationships via water/solvent/component inter-diffusion and infiltration in the cell wall matrix: A new synchrotron-based x-ray fluorescence mapping capability at Argonne National Laboratory was utilized to map adhesive infiltration in wood cell walls. The result was a 2D map of adhesive infiltration from the bondline deep into the wood. The maps coupled with nanoindentation across the bondline revealed that lower molecular weight adhesives penetrated farther, hardness and modulus values were directly proportional to infiltration, and that infiltration decreased moisture induced softening of the wood. Additional, research on this topic with four different adhesive bondlines revealed that phenol formaldehyde and urea formaldehyde increased the hardness of bondlines near but not at the adhesives. This indicates diffusion and cure of these adhesives deeper into the wood substrate. This was not observed for epoxy or emulsion polymer isocyanate adhesives a result that is consistent with lower macro observations of durability of these wood adhesives. In support of the above described research we also investigated the through-thickness hardness and modulus of Zr50Cu45Al5 metallic glass melt-spun ribbon. Hardness and modulus were found to vary linearly across the thickness with the side of the ribbon that cooled most quickly having the highest hardness and modulus. The variation was nullified upon annealing the glass. Utilizing cell wall polymers from trees and plants for bio-resins and bio-energy: Oxidative cleavage of the recalcitrant plant polymer lignin is a crucial step in global carbon cycling, and is accomplished most efficiently by fungi that cause white rot of wood. We grew Phanerochaete chrysosporium on wood sections in the presence of oxidant-sensing beads based on the ratiometric fluorescent dye BODIPY 581/591. The results showed that oxidation gradients occurred around the hyphae, and data analysis using a mathematical reaction-diffusion model indicated that the dominant oxidant during incipient white rot had a half-life under 0.1 s. The best available hypothesis is that this oxidant is the cation radical of the secreted P.⿿chrysosporium metabolite veratryl alcohol.

Impacts
Discoloration of wood flour research greatly assists in the understanding of the effect of extractives and lignin on the properties of WF for use in wood-plastic composites (WPCs). Cell wall bundles demonstrate proof of a high specific torque actuator with large angles of rotation and shape memory twist capabilities can be fabricated from wood and opens up opportunities for microactuators, sensors, and energy harvesters. Wood penetration images support optimization of wood composite manufacturing by elucidating adhesive make up and processing conditions that enhance penetration and performance. Fluorescent microsensors distributed on wood undergoing fugal attach help to elucidate key step in the decay mechanism thereby raising new hope for target fungicides.

Publications

  • Hunt, Christopher G.; Houtman, Carl J.; Jones, Don C.; Kitin, Peter; Korripally, Premsagar; Hammel, Kenneth E. 2013. Spatial mapping of extracellular oxidant production by a white rot basidiomycete on wood reveals details of ligninolytic mechanism. Environmental Microbiology. 15(3): 956⿿966.
  • Ibach, Rebecca E.; Rowell, Roger M. 2013. Lumen modifications. In: Rowell, Roger, ed. Handbood of wood chemistry and wood composites, Second edition. Boca Raton, FL: CRC Press: 599-625. Chapter 16.
  • Jakes, Joseph E.; Gleber, Sophie-Charlotte; Vogt, Stephan; Hunt, Chris G.; Yelle, Dan; Grigsby, Warren; Frihart, Chuck. 2013. New syncrotron-based technique to map adhesive infiltration in wood cell walls. In: Proceedings of the 36th Annual Meeting of the Adhesion Society. 2013 March 3-6; Daytona Beach, FL. Bethesda, MD: The Adhesion Society Inc. 3 p. Available online at http://adhesionsociety.org/program2013/
  • Chen, Yao; Tshabalala, Mandla A.; Stark, Nicole M.; Gao, Jianmin; Fan, Yongming; Ibach, Rebecca E. 2013. Thermal properties of extracted and delignified wood flour for use in wood-plastic composites. In: Conference Proceedings, The Advancements in Fiber-Polymer Composites: Wood Fiber, Natural Fibers and Nanocellulose. 2013 May 6-7; Milwaukee, WI. Madison, WI: Forest Products Society: 10 p.
  • Marcott, Curtis; Lo, Michael; Kjoller, Kevin; Prater, Craig; Shetty, Roshan; Jakes, Joseph; Noda, Isao. 2012. Nanoscale infrared spectroscopy of biopolymeric materials. In: SAMPE Technical Conference Proceedings: Navigating the global landscape for the new composites. 2012 October 22-25; Charleston, SC. Covina, CA: Society for the Advancement of Material and Process Engineering: 9 pp. CD ROM.
  • Melgarejo, Z. Humberto; Jakes, J.E.; Hwang, J.; Kalay, Y.E.; Kramer, M.J.; Voyles, P.M.; Stone, D.S. 2012. Variation of hardness and modulus across thickness of Zr-Cu-Al metallic glass ribbons. In: Materials Research Society Symposium Proceedings. Vol. 1520. 6 pp. Doi: 10.1557/opl.2012.1690.
  • Plaza, Nayomi; Zelinka, Samuel L.; Stone, Don S.; Jakes, Joseph E. 2013. Plant-based torsional actuator with memory. Smart Materials and Structures 22: 1-7.
  • Rowell, Roger M.; Pettersen, Roger; Tshabalala, Mandla A. 2013. Cell wall chemistry. In: Rowell, Roger. ed. Handbook of wood chemistry and wood composites, Second edition. Boca Raton, FL: CRC Press: 33-72. Chapter 3.
  • Tshabalala, Mandla A.; Jakes, Joseph; VanLandingham, Mark R.; Wang, Shaoxia; Peltonen, Jouko. 2013. Surface characterization. In: Rowell, Roger. ed. Handbook of wood chemistry and wood composites, Second edition. Boca Raton, FL: CRC Press: 217-252. Chapter 8.
  • Yelle, Daniel J. 2013. Elucidating how wood adhesives bond to wood cell walls using high-resolution solution-state NMR spectroscopy. In: Proceedings of the 36th Annual Meeting of the Adhesion Society. 2013 March 3-6; Daytona Beach, FL. Bethesda, MD: The Adhesion Society Inc. 4 p. Available online at http://adhesionsociety.org/program2013/
  • Yu, Yan; Frihart, C.R.; Jakes, J.E.; Jiang, Z.H. 2012. Mechanical characterization of wood-adhesive interphase with an improved nanoindentation technique. In: Proceedings of the 55th international convention of Society of Wood Science Technology. 2012 August 27-31; Beijing, China. Paper AP2-8: 6 p.