Title: Acoustic measurements on trees and logs: a review and analysis

Author: Wang, Xiping; 

Date: 2013

Source: Wood Sci Technol Volume 47, 2013; pp. 965-975.

Publication Series: Scientific Journal (JRNL)

Description: Acoustic technologies have been well established as material evaluation tools in the past several decades, and their use has become widely accepted in the forest products industry for online quality control and products grading. Recent research developments on acoustic sensing technology offer further opportunities to evaluate standing trees and logs for general wood quality and intrinsic wood properties. Although the concept of using acoustic velocity as an effective measure of stiffness applies to both standing trees and felled logs, the method typically used to measure acoustic velocity in trees is different from that used in logs. Consequently, there is a significant difference in measured velocity values between trees and logs. Other factors affecting tree-log velocity relationships include tree diameter, stand age, operating temperature, and wood moisture content. This paper presents the fundamentals of acoustic wave propagation in trees and logs and discusses two different mechanisms of acoustic velocity measurement, time-of-flight for standing trees and resonance for logs. Experimental data from previous studies are reviewed and analyzed to examine the strength of the tree-log velocity relationships and discuss the factors that influence tree velocity deviation.

Keywords: Acoustic velocity, acoustic waves, logs, resonance, time-of-flight, trees

Publication Notes:

• We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
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Wang, Xiping. 2013. Acoustic measurements on trees and logs: A review and analysis. Wood Science Technolology 47: 965-975.

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https://www.treesearch.fs.fed.us/pubs/44037

Title: A comparative study of cellulose nanofibrils disintegrated via multiple processing approaches

Author: Qing, Yan; Sabo, Ronald; Zhu, J.Y.; Agarwal, Umesh; Cai, Zhiyong; Wu, Yiqiang; 

Date: 2013

Source: Carbohydrate Polymers, Volume 97, 2013; pp. 226-234. 

Publication Series: Scientific Journal (JRNL)

Description: Various cellulose nanofibrils (CNFs) created by refining and microfluidization, in combination withenzymatic or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized pretreatment were compared. Themorphological properties, degree of polymerization, and crystallinity for the obtained nanofibrils, aswell as physical and mechanical properties of the corresponding films were evaluated. Compared torefining, intense microfluidization contributed greater separation of nanofibril bundles, which led to anenhancement of mechanical strength and transparency for the resultant film. The selected enzymaticpre-treatments produced shortened fibers due to preferential hydrolysis of amorphous cellulose and,in combination with mechanical treatments, resulted in short and stiff cellulose nanocrystal (CNC)-like materials. Despite films from these CNC-like fibrils having inferior tensile strength, their tensile modulus and transparency were significantly improved compared to CNFs prepared without pre-treatment.The unique fiber morphology and high crystallinity potentially offer a green and ecologically friendlyalternative for the preparation of CNCs and CNFs as part of an integrated biorefinery approach.

Keywords: Cellulose nanofibrils, Refining, Microfluidization, Enzymatic and chemical pretreatments

Publication Notes:

• We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
• This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

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Citation:

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Qing, Yan; Sabo, Ronald; Zhu, J.Y.; Agarwal, Umesh; Cai, Zhiyong; Wu, Yiqiang. 2013. A comparative study of cellulose nanofibrils disintegrated via multiple processing approaches. Carbohydrate Polymers. 97: 226-234.

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https://www.treesearch.fs.fed.us/pubs/43947

SHORT CELLULOSE NANOFIBRIL/POLYVINYL ALCOHOL NANOCOMPOSITE FIBERS

Author

Jun Peng1,2, Craig Clemons3*, Ronald Sabo3, Tom Ellingham1,2, Lih-Sheng Turng1,2* Polymer Engineering Center, University of Wisconsin–Madison, Madison, Wisconsin 53706
Wisconsin Institute for Discovery, University of Wisconsin–Madison, Madison, Wisconsin 53715 3USDA Forest Service, Forest Products Laboratory, Madison, WI 53726 

Abstract

methylpiperidine-1-oxy radical (TEMPO)-mediated oxid- ation as a pretreatment prior to mechanical disintegration. They found the tensile strength did not improve with the addition of 1 wt% CNF [4]. A higher CNF content may have led to greater reinforcement. However, it was not possible to add more CNF due to the difficulty in dis- persing the high-aspect-ratio CNF even with intense ultra- sonication or strong mechanical stirring.
In this study, we investigated short cellulose nano- fibers (SCNF) that were mechanically isolated from enzymatically pretreated wood pulp as a reinforcement for the PVA fiber. Sufficient mechanical energy was used to prepare discrete CNF that could be used at higher weight percentages but without the need for concentrated sulfuric acid hydrolysis, as in CNC production, or the loss of hydroxyl groups for hydrogen bonding with the PVA matrix. Ultimately, we hoped to optimize the enzyme mixtures and pretreating conditions to minimize the mechanical energy needed to produce the SCNF.

Experiments
Preparation of Short Cellulose Nanofibrils (SCNF)
SCNF was prepared at the U.S. Forest Service Forest Products Laboratory (Madison, WI), according to the procedure described by Qing et al. [5]. The 1 wt% SCNF suspension was prepared to act as a reinforcing agent.

Preparation of Spinning Solution
A 99% hydrolyzed commercial-grade of PVA from Sigma-Aldrich with a weight-average molecular weight of 85,000 to 124,000 was used as the matrix polymer. A sufficient amount of PVA was dissolved in water at 90 oC with mechanical stirring for 30 min to yield 20% PVA by weight. Spinning solutions were prepared by mixing various amounts of SCNF solution, PVA solution, and water at 90oC for 60 min. Specific compositions are listed in Table 1.

Table 1. Compositions of PVA/SCNF spinning solutions and dry fiber.

Short cellulose nanofibrils (SCNF) were investigated as a reinforcement for polyvinyl alcohol (PVA) fibers. SCNF fibers were mechanically isolated from hard wood pulp after enzymatic pretreatment. Various levels of SCNF were added to PVA and gel-spun into continuous fibers. The molecular orientation of PVA was affected by a combination of wet drawing during gel spinning and post-hot-drawing at a high temperature after drying. A maximum total draw ratio of 27 was achieved with various SCNF contents investigated. The PVA crystal orientation increased when small amounts of SCNF were added, but decreased again as the SCNF content was increased above about 2 or 3%, likely due to SCNF percolation resulting in network formation that inhibited alignment. SCNF fillers were effective in improving PVA fiber tensile properties (i.e., ultimate strength and elastic modulus). Shifts in the Raman peak at ~1095 cm-1, which were associated with the C–O–C glycosidic bond of SCNF, indicated good stress transfer between the SCNF and the PVA matrix due to strong interfacial hydrogen bonding.

Introduction
Nanocellulose-based reinforcements constitute a new class of naturally-sourced reinforcements. Trees, plants, some marine creatures such as tunicates, and certain bacteria and algae form microfibrils from cellulose mole- cules. These microfibrils have a complex structural hierarchy and often act as the main reinforcing element in their respective organisms [1]. In part, this is the high reinforcing potential of native crystalline cellulose within these microfibrils that has recently led researchers to ex- tract nanocellulose from them for use in composites.

To improve the mechanical properties of PVA fibers, both CNC and CNF have been investigated as reinforce- ments. Uddin et al. [2] produced wet spun fibers from aqueous PVA solutions with more than 30% CNC, followed by hot drawing [2]. Adding 5% CNC increased the ultimate tensile strength 20% compared to neat PVA fibers. However, the tensile strength was reduced at concentrations above 5% as orientation was reduced. Peresin et al. produced PVA mats with up to 15% CNC by electrospinning and found that CNC increased the storage modulus [3]. However, properties such as fiber strength or tenacity were not measured. Endo et al. gel-spun PVA that was reinforced with CNFs prepared using 2,2,6,6-tetra-methylpiperidine-1-oxy radical (TEMPO)-mediated oxid- ation as a pretreatment prior to mechanical disintegration. They found the tensile strength did not improve with the addition of 1 wt% CNF [4]. A higher CNF content may have led to greater reinforcement. However, it was not possible to add more CNF due to the difficulty in dis- persing the high-aspect-ratio CNF even with intense ultra- sonication or strong mechanical stirring.

In this study, we investigated short cellulose nano- fibers (SCNF) that were mechanically isolated from enzymatically pretreated wood pulp as a reinforcement for the PVA fiber. Sufficient mechanical energy was used to prepare discrete CNF that could be used at higher weight percentages but without the need for concentrated sulfuric acid hydrolysis, as in CNC production, or the loss of hydroxyl groups for hydrogen bonding with the PVA matrix. Ultimately, we hoped to optimize the enzyme mixtures and pretreating conditions to minimize the mechanical energy needed to produce the SCNF.

Experiments
Preparation of Short Cellulose Nanofibrils (SCNF)
SCNF was prepared at the U.S. Forest Service Forest Products Laboratory (Madison, WI), according to the procedure described by Qing et al. [5]. The 1 wt% SCNF suspension was prepared to act as a reinforcing agent. 

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https://www.fpl.fs.fed.us/documnts/pdf2014/fpl_2014_peng001.pdf

Nanotechnology and Forest Products

A leader in wood products 

research for over a century, the FPL is fast becoming the lead Federal research facility for the application of nanotechnology in forest products. The opening of FPL's Nanocellulose Pilot Plant in 2012 has garnered worldwide recognition by industry specialists and the popular press.
Using structural, chemical, and mechanical techniques, interdisciplinary teams of scientists scientists continue to expand FPL's nanocellulose research program.
From industry advocate TAPPI - Two overviews of nanotechnology applications related to wood and wood products
Video Nanocellulose, Rethink Paper	Webinar Renewable and sustainable nanomaterials

What is nanotechnology?

Nanotechnology is a multi-disciplinary field of applied science and technology. The general theme is understanding and engineering matter at the atomic and molecular scales. The nanoscale ranges from 1 to 100 nanometers in at least one dimension. A nanometer is a billionth of a meter, or about 80,000 times thinner than a typical human hair. This is not merely the study of small things, however. It is the research and development of materials, devices, and systems exhibiting physical, chemical, and biological properties different from those found at larger scales. FPL scientists are conducting nanoscale research to learn more about the fundamental components of wood. The ability to organize, characterize, and manipulate matter at the nanoscale has launched a revolution in science, engineering, and technology. These unique properties are what make potential nanomaterials and nanotechnology so promising to scientists and engineers. With careful attention to potential risks and promising rewards, nanotechnology has massive potential to drive global economic growth.

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https://www.fpl.fs.fed.us/research/research_emphasis_areas/introduction.php?rea_id=4

Water, Air, and Soil

The edible black poplar mushroom, Agrocybe aegerita. Forest Service Snapshot: Forest fungi perform an essential role in recycling woody plant debris and have many potential applications in biotechnology. In 2009, a Forest Products Laboratory chemist worked for ten months as a Senior Fulbright Awardee at the International Graduate School in Zittau, Germany. The research, conducted in collaboration the German scientists, dealt with a recently discovered and unusual enzyme secreted by Agrocybe aegerita, otherwise known as the edible black poplar mushroom.

Summary:  Forest fungi perform an essential role in recycling woody plant debris and have many potential applications in biotechnology. In 2009, a Forest Products Laboratory chemist worked for ten months as a Senior Fulbright Awardee at the International Graduate School in Zittau, Germany. The research, conducted in collaboration the German scientists, dealt with a recently discovered and unusual enzyme secreted by Agrocybe aegerita, otherwise known as the edible black poplar mushroom. The results showed that this enzyme, known as a peroxygenase, degraded some ethers that have emerged as serious environmental pollutants. Notably, the peroxygenase oxidized dioxane and tetrahydrofuran, both of which are widespread groundwater contaminants. This work points out the importance of forest fungi as natural cleanup agents in the environment, and opens the possibility that their enzymes might be used to detoxify polluted water.	Princpal Investigator(s):   Hammel, Kenneth E. Research Location:  Global Fiscal Year: 2010 Highlight ID: 176
Related Research Emphasis Areas: Woody Biomass Utilization

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https://www.fpl.fs.fed.us/research/highlights/highlight.php?high_id=176

Recalculating the Decay Hazard Index

Snapshot: Climate index values for estimating decay hazard to wood exposed outdoors above ground, commonly known as Scheffer index values, were calculated for 280 locations in the United States (270 locations in the conterminous United States) using the most current climate data available from the National Climatic Data Center.

Summary:  Climate index values for estimating decay hazard to wood exposed outdoors above ground, commonly known as Scheffer index values, were calculated for 280 locations in the United States (270 locations in the conterminous United States) using the most current climate data available from the National Climatic Data Center. These were data for the period 1971-2000. The values generally appear to have been moderately higher during this period than the values listed originally by Scheffer. A revised climate index map has been drawn based on the data.	Princpal Investigator(s):   Carll, Charlie G. Research Location:  nationwide Fiscal Year: 2010 Highlight ID: 171
Related Research Emphasis Areas: Woody Biomass Utilization

For further details log on website :
https://www.fpl.fs.fed.us/research/highlights/highlight.php?high_id=171

Heat Sterilization of Firewood for Thermal Eradication of Emerald Ash Borer

Snapshot: FPL researchers have led a joint research effort with USDA APHIS and state regulatory staff to evaluate various heat treatment options and heating times for ash firewood and help firewood industry to successfully implement the heat treatment process as required by the new USDA phytosanitary regulations.

Summary:  The emerald ash borer (EAB) is a non-native bark- and wood-infesting insect that poses an enormous threat to North American urban and rural forests. Because of the potential risk associated with moving ash firewood infested with EAB, the interstate movement of all hardwood firewood is restricted under Federal quarantine. Communities and firewood producers are faced with challenges on implementing heat sterilization process and safely treating their firewood for interstate commerce. Working with the wood engineering group at the University of Minnesota Duluth, FPL researchers have led a joint research effort with USDA APHIS and state regulatory staff to evaluate various heat-treatment options and heating times for ash firewood and help firewood industry to successfully implement the heat treatment process as required by the new USDA phytosanitary regulations. The completion of laboratory experiments and field trials has resulted in practical and effective heat treating schedules for thermally eradicating EAB and other non-native invasive species in firewood. The information benefits firewood producers in planning and executing effective heat-treatment on hardwood firewood and help USDA APHIS and state government to develop feasible certification and auditing protocols for better enforcing the federal regulations. The team has also conducted heat-treatment demonstrations at four firewood treating facilities in Wisconsin, Illinois, and Indiana. An on-site training workshop and a web-based training seminar were conducted and well received by firewood producers and APHIS and state field regulatory staff.	Princpal Investigator(s):   Wang, Xiping Research Location:  Minnesota External Partners:  University of Minnesota-Duluth Fiscal Year: 2010 Highlight ID: 185
Related Research Emphasis Areas: Woody Biomass Utilization

For further details log on website :
https://www.fpl.fs.fed.us/research/highlights/highlight.php?high_id=185

Estimation of environmental emissions associated with U.S. production of lumber and wood panel products including harvesting, forest regeneration, transport and manufacturing

Snapshot: Life-cycle research on wood products plays a vital role in developing strategies for mitigating climate change. The main driving force behind climate change has been the release of greenhouse gases such as carbon dioxide (CO2) into the atmosphere. Unlike nonrenewable materials, renewable materials such as wood products burn woody biomass for energy thus helping offset the burning of fossil fuels during its manufacturing. In addition, wood products are made from trees that reabsorb CO2 emitted during manufacturing thus closing the carbon cycle. This project evaluated the extent of offsetting demand for fossil fuels by burning woody biomass for energy.

Summary:  Life-cycle research on wood products plays a vital role in developing strategies for mitigating climate change. The main driving force behind climate change has been the release of greenhouse gases such as carbon dioxide (CO2) into the atmosphere. Unlike nonrenewable materials, renewable materials such as wood products burn woody biomass for energy thus helping offset the burning of fossil fuels during its manufacturing. In addition, wood products are made from trees that reabsorb CO2 emitted during manufacturing thus closing the carbon cycle. This project evaluated the extent of offsetting demand for fossil fuels by burning woody biomass for energy. The primary method to determine the amount and type of CO2 released into the atmosphere is by life-cycle assessment (LCA). Life-cycle inventory (LCI), a major component of LCA, tracks all material and energy inputs and outputs flowing into and out of a system boundary. For a 'cradle-to-gate' LCI, the product is tracked from the forest (i.e. a tree) to the final product leaving the gate of a manufacturing facility. This LCI project examined a number of wood products made in the United States such as softwood lumber, hardwood lumber, and solid hardwood flooring. Results showed burning woody biomass for energy during manufacturing for all these wood products greatly reduces the environmental burdens by offsetting demand for fossil fuels. This project was part of a larger initiative conducted by the Consortium for Research on Renewable Industrial Materials (CORRIM). CORRIM (www.corrim.org) includes 15 research institutions and focuses on the effects of producing and using renewable materials.	External Partners:  Consortium for Research on Renewable Industrial Materials Fiscal Year: 2010 Highlight ID: 159
Related Research Emphasis Areas: Woody Biomass Utilization

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https://www.fpl.fs.fed.us/research/highlights/highlight.php?high_id=159

Characterizing cellular properties in wood to better understand bulk wood properties

Snapshot: A current aim in forest products research is to efficiently modify wood to tailor it for specific end uses, such as hardening softwoods for flooring or softening wood in pretreatments for biorefineries.

Summary:  A current aim in forest products research is to efficiently modify wood to tailor it for specific end uses, such as hardening softwoods for flooring or softening wood in pretreatments for biorefineries. Research efforts in these areas are hindered by a lack of understanding of how wood modifications cause changes in bulk wood properties. Bulk wood properties derive from an ensemble of processes taking place at smaller length-scales, and therefore, to understand how wood modifications affect wood properties, techniques to characterize wood at these smaller length-scales are needed. To characterize wood at the cellular level, researchers at FPL, in cooperation with researchers at the University of Wisconsin, have developed a unique set of nanoindentation tools to probe the micron-size domains in wood cell walls. These tools account for the effects of edges near the nanoindents and assess the elastic and plastic properties of cell walls over a wide range of time-scales. These techniques are being used to understand wood modifications to improve current forest products and develop new products.	External Partners:  University of Wisconsin Fiscal Year: 2010 Highlight ID: 189
Related Research Emphasis Areas: Woody Biomass Utilization

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https://www.fpl.fs.fed.us/research/highlights/highlight.php?high_id=189

Rice Straw Particleboard

Rice straw appears to be a promising agricultural residue for manufacturing composite panels. William M. Brown Jr., Bugwood.org Snapshot: There has recently been a revival of interest in using agriculture residues to produce particleboards and other composite panels due to competition for wood raw materials and for economical and environmental considerations. This study looks at the effect of various pretreatments on the performance of rice straw particleboard. Additionally, carbohydrates extracted from rice straw particles could be a potential sustainable resource for biofuel or bio-based chemicals.

Summary:  Particleboards are widely used for construction, furniture, and interior decoration. The primary material used in the particleboard panel industry is wood, but there has recently been a revival of interest in using agriculture residues to produce particleboards and other composite panels due to competition for wood raw materials and for economical and environmental considerations. Globally, wheat and rice are the most important food grains ranking second and third in terms of the total cereal production, and appear to be the most promising agriculture residues for manufacturing composite panels. The objective of this study is to evaluate the effect of oxalic acid (OA) - and steam-pretreatment on the primary performance of rice straw particleboards. In addition, the effect of various treatment conditions on carbohydrates released from rice straw particles was investigated. The results show that steam- and short durations of OA-treatment significantly improved the mechanical properties and dimensional stability of rice straw particleboards. However, steam-treated rice straw (without OA-treatment) panels exhibited even better performance when compared with OA-treated panels. OA-pretreatment time has a negative effect on performance of panels, whereas the effect of temperature on the performance of OA-treated panels was not significant, except for the linear expansion. OA-treatment accelerated carbohydrates extraction. The sugars released from the OA-treated rice straw particles increase with increasing treatment temperature and time. Carbohydrates extracted from rice straw particles could be a potential sustainable resource for biofuel or bio-based chemicals.	Princpal Investigator(s):   Cai, Zhiyong External Partners:  Central South University of Forestry and Technology, China Fiscal Year: 2011 Highlight ID: 308
Related Research Emphasis Areas: Woody Biomass Utilization
Resources: Effect of oxalic acid and steam pretreatment on the primary properties of UF-bonded rice straw particleboards (publication)

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https://www.fpl.fs.fed.us/research/highlights/highlight.php?high_id=308