Fundamental and Integrated Experiments of Wood Science (木材科学综合实验)

Fundamental and Integrated Experiments of Wood Science (木材科学综合实验)

Course statement:

This course is accompanied by the co-requisite ‘Wood Science and Technology’. The course explores some of the key experiments in the research of wood science and technology including structural section, chemical section, physical and mechanical section.Activities in this course will bring students with an understanding of

1)The microscopic and macroscopic anatomy of woodand non-wood plants,

2)How to identify important Chinese wood species and some exotic species,

3)The important chemical, physical and mechanical properties of wood and non-wood plants.

Prerequisites:

1)B.S. in forestry and forestry engineering, or equivalent.

2)Fluent in listening, speaking and writing English.

3)Willingness to engage yourself in participatory learning.

Total Time Required for course:

45 minutes/lesson, 32 lessons

Setting:

4201 Laboratory

Final Grade:

The final grade will be calculated based on the following distribution: 50% laboratory assignments, 30% laboratory reports and 20% quizzes.

Topic lectures:

Totally, this course will have 11 lectures. Each lecture will be 2 or 4 lessons.

For structuralsection:

1)Macroscopic observation of softwood and hardwood (4 lessons)

2)Temporary and permanent slides preparation (4 lessons)

3)Microscopic observation of softwood and hardwood (4 lessons)

4)Wood identification (2 lessons)

5)Morphological characteristics of wood/non-wood fibers (2 lessons)

6)SEM observation of wood/non-wood plants (2 lessons)

For chemical section:

1)Holo-cellulose content of wood/non-wood plants (2 lessons)

2)Cellulose content of wood/non-wood plants (2 lessons)

3)Klason lignin content of wood/non-wood plants (2 lessons)

For physical and mechanical section:

1)Density of wood & water content of wood (2 lessons)

2)Mechanical properties of wood (6 lessons)

Lab Safety:

1)Do not use excessive force when trying to cut samples - this is when accidents happen.Do not cut towards any part of your body. Retract/fold the blade of your knife when it is not in use. Please get in the habit of retracting the blade when you put your knife down on the table or bench.

2)Be careful when using glassware. Cuts and burns are the most common injuries that occur in chemistry laboratories.

3)Wash chemicals from skin. If you receive a chemical burn from a caustic material, i.e. acid or base, immediately wash the burned area with large quantities of water.

4)Always wash your hands, before leaving the lab since toxic chemicals may be transferred to the mouth at a later time.

5)Never point a test tube toward a laboratory neighbor or yourself when heating a test tube over a burner.

6)Wear suitable clothing. Wear clothing that will protect you against spilled chemicals or flaming liquids.

7)Clean up your workspace at the end of each laboratory period.

References:

1)Wheeler, E.A., Baas P. and Gasson P.E. 1989. IAWA list of microscopic features for hardwood identification. IAWA Bulletin n.s. 10(3): 219-332.

2)Richter, H.G., Grosser, D, Heinz, I. and Gasson, P.E. 2004. IAWA list of microscopic features for softwood identification. IAWA Journal 25(1): 1-70.

3)Panshin, A.J. and C. deZeeuw. 1980. Textbook of Wood Technology. 4th Ed. McGraw-Hill Book Co., New York.

4)USDAForest Products Laboratory, Center for Wood Anatomy Research, Madison, Wisconsin.

5)Inside Wood: Wood Anatomy Links. North CarolinaStateUniversity.

1.Structural section

1.1Macroscopic observation of softwood and hardwood

Purpose:

For the student to become familiar with the transverse, radial and tangential sections of wood; recognizing pith and bark, earlywood and latewood, heartwood and sapwood, porous wood and non-porous wood, ray and resin canal in three sections of wood; comparing differences of softwood and hardwood by naked-eyes and loupe; distinguishing vessel arrangement and banded parenchyma of different hardwood. These skills are foundational to the course and will be used extensively throughout.

Material:

1)Softwood (Pinus massoniana, Pinus koraiensis, Larix dahurica, Picea jezocnsis, Cunninghamia lanceolata, Abies nephrolepis,Taxus Specisa);

2)Hardwood (Quercus acutissima, Liquidambar formosana, Castanopsis cuspidate, Betula platyphylla, Zelkova schneideriana, Cinnamomum camphora, Sassafras tzumu);

3)Single-edge razor blades;

4)Loupe (x10).

1.2Temporary and permanent slides preparation

Purpose:

For the student to become familiar with the sectioning and staining techniques used with different woodand no-wood materials. A variety of materials stains and sectioning materials have been provided.Students should explore the use of these materials to perform the temporary and permanent slides preparation techniques.

Material:

Excavated wooden objects;

Bamboo;

Poplar;

Chinese-fir;

Plain glass microscope slides;

Cover glasses;

Single-edge razor blades;

Double-edge razor blades;

Sliding microtome;

Aqueous gum-chloral;

Canada balsam;

Forceps;

Pipette.

1.3Microscopic observation of softwood and hardwood

Purpose:

For the student to become familiar and comfortable with the use of the microscopes, get familiar with microscopic features for softwood and hardwood on transverse, radial and tangential sections.

Material:

Standard microscope slides;

Light microscope.

1.4Wood identification

Purpose:

For the student to become familiar with the terminology and basic characteristics that need to know to identify the wood of angiosperms and gymnosperms.Students will demonstrate the ability to identify commercial woods using macroscopic and microscopic techniques

Material:

Common commercial woods;

Loupe;

Single-edge razor blades;

Double-edge razor blades;

Plain glass microscope slides;

Cover glasses;

Light microscope.

1.5Morphological characteristics of wood/non-wood fibers

Purpose:

For the student tobecome familiar with the three-dimensional form of wood/non-wood fibers. Fiber dimensions including fiber length, fiber width and cell wall thickness need be measured.

Material:

Small pieces of wood/non-wood plant;

Plain glass microscope slides;

Cover glasses;

Light microscope;

Hydrogen peroxide;

Acetic acid.

Technique:

Cut small pieces of wood/non-wood plant into a mixture of hydrogen peroxide and acetic acid (1:1). Cook the mixture in a 56-60 degree oven for 1 hours. If further macerating is needed, replace the old fluid with a fresh mixture and cook the tissues for another 1 hours. Repeat the process until the material is mostly colorless, and may be easily teased apart with a dissecting probe. When the maceration is complete, rinse the tissues in water in an uncovered container. Stain in 0.25% Safranin in water and mount in dilute glycerin.

1.6SEM observation of wood/non-wood plant

Purpose:

For the student tobecome familiar with the cellular composition and organization of hardwoods and softwoods, and the structure of the wood cell wall by SEM observation.

Material:

Small blocks of softwood and hardwood;

Charcoal;

Cellulose nanofibril film;

Bamboo block;

Straw;

Paper;

Pollen;

SEM (Hitachi TM-1000).

2.Chemical section

2.1Holo-cellulose content of wood/non-wood plants

Purpose:

Cellulose, hemicellulose and lignin make up a major portion of biomass samples. These constituentsmust be measured as part of a comprehensive biomass analysis. This experiment is for the student to know the Wise method for calculating the holo-cellulose content of wood/non-wood plant.

Material:

Small pieces of wood/non-wood plant (de-waxed samples);

250mL flask;

25mL flask;

1G2 glass filter;

1000mL filtration bottle;

Vacuum pump;

Water bath;

Oven;

Glacial acetic acid;

Sodium chlorite;

Distilled water.

2.2Cellulose content of wood/non-wood plants

Purpose:

The main component of the plant cell wall is cellulose, which represents almost 50 percent of the total cell wall material. Cellulose – a long chain-shaped molecule which consists of several thousand monosaccharides that assemble themselves to form extremely tear-resistant bundles known as microfibrils. These cellulose microfibrils surround the plant cell like steel cables and give it shape and stability. This experiment is for the student to familiar with the method for calculating the cellulose content of wood/non-wood plant.

Material:

Small pieces of wood/non-wood plant (de-waxed samples);

250mL flask;

1G2 glass filter;

1000mL filtration bottle;

Spherical condenser tube;

Desiccator;

Vacuum pump;

Water bath;

Oven;

95% Ethanol;

Nitric acid;

Distilled water.

2.3Klason lignin of wood/non-wood plants

Purpose:

Lignin is a compound that is highly abundant in a range of plant species and heavily shapes the ecological niche of such plants. It can take up to 20% of the leaf biomass of woody species, and up to 30% in tree trunks. Although ecologically highly relevant, it is not so easy to determine the concentration of lignin. Two methods have been applied frequently. First, plant material is treated with increasingly stronger and more aggressive chemicals, until a fraction remains that is even not dissolved in 72% H2SO4. This residue is determined gravimetrically and termed 'Klason' lignin.Alternatively, plant material can digested with methylbromide, after which the building blocks, the three monolignols, are formed again (Morison 1972). Because of their aromatic nature, they absorb in the UV band, and by assuming that these building blocks represent a certain proportion of the total mass of lignin, an estimate of the lignin concentration in the original material can be made. For non-invasive methods, see Hatfield & Fukushima (2005).

This experiment is for the student tofamiliar with the method foranalyzingthe acid insoluble lignin (Klason lignin) content of wood/non-wood plants.

Material:

Small pieces of wood/non-wood plant (de-waxed samples);

1000mL flask;

100mL grinding mouth flask with glass stopper;

1G3 glass filter;

Measuring bottle;

Desiccator;

Vacuum pump;

Water bath;

Electric stove;

Oven;

Distilled water.

3.Physical section

3.1Density of wood & water content of wood

Purpose:

Knowledge of the true density of wood substance and of its apparent densities in different liquids and gases is of considerable importance. Such information should help in giving some idea of the nature of the colloidal and the molecular dispersion of the materials making up the cell wall. The purpose of this experiment is to determine the water contentand the density of a set of wooden blocks.

Material:

A set of wooden blocks;

Metric ruler;

Balance;

Oven.

3.2Mechanical properties of wood

Purpose:

The mechanical properties of wood are its fitness and ability to resist applied or external forces. By external force is meant any force outside of a given piece of material tends to deform it in any manner. Wood with greater resistance in applied forces will have higher strength. Besides, the ability of wood to resist the load applied is depends on the magnitude and direction of the forces such as compression, tensile and shear.This experiment is

1)To introduce some basic lab techniques for mechanical testing.

2)To learn about the importance of mechanical properties of wood.

3)To determine the MOR and MOE of a wood through the wood strength and flexibility properties.

4)To study the difference of density and moisture content will affect the MOR and MOE.

5)To learn the method of using Instron equipment in order to test the wood strength.

Material:

A set of wood specimens;

Instron machine;

Ruler;

Oven.

Terminology:

Modulus of elasticity (MOE) or Young's modulus is the ratio of the stress orstretching force per unit cross sectional area to the strain or amount of stretching perunit of length. Within the elastic range below the proportional limit, this ratio is aconstant for a given piece of wood, making it useful in staticbending tests fordetermining the relative stiffness of a board. Themodulus of elasticity is normallymeasured in Newton per square meter (N/m²) or pounds per square inch (psi).

Modulus of rupture (MOR) is the maximum load carrying capacity of amember. It is generally used in tests of bending strength to quantify the stress requiredto cause failure.Elasticity implies that deformations produced by low stress are completelyrecoverable after loads are removed. When loaded to higher stress levels, plasticdeformation or failure occurs.There are three kinds of internal stresses, namely tensile, compressive andshearing.

Tensile strengthcan be measured eitherparallel orperpendicular to grain. Tensile strength parallel to grain normally is 50 times stronger thanperpendicular to grain. There is not muchdifferent between radial or tangentialdirection.

Compression strengthcan be either parallel to grain or perpendicular to grain.Compression strength parallel to grain normally is15 times higher than perpendicular tograin. Compression strength is half of tensile strength. It is mostly due to failure inwood cell wall due to shear failure or cleavage in the cell.

Shear strength is the ability to resist internal slipping of one part upon another alongthe grain.Shear strength can be either parallel to grain or perpendicular to grain. Normally it isoccur during wood under bending loading. Perpendicular to grain is3-4 times higherthan parallel to grain.

Bending strength is the ability of wood to resist the forces that bend the wood.Woods under bending strength have combination of stresses such as tensile,compression and shear. Tensile tend to lengthen the sample while compression tend toshorten the sample. Shear will tend to split the wood. MOE of wood perpendicular tograin is about 1/50 the value of MOE parallel to grain.

PAN Biao & ZHAI Sheng-cheng

College ofMaterials Science and Engeering

Nanjing Forestry University

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Samples containing extractives are not suitable for this procedure. Extractives will partition irreproducibly, resulting in a high lignin bias.

 Morrison IM (1972) A semi-micro method for the determination of lignin and its use in predicting the digestibility of forage crops. J. Sci. Food Agric. 23, 455-463.



Hatfield R & Fukushima RS (2005) Can Lignin Be Accurately Measured? Crop Sci. 45: 832-839.

