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NOTE TAKER NEEDED. "Disability Resources for Students (DRS) is looking for a notetaker for this class to assist a student who is unable to take complete class notes because of the effects of a disability. - PowerPoint PPT Presentation
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"Disability Resources for Students (DRS) is looking for a notetaker for this class to assist a student who is unable to take complete class notes because of the effects of a disability.
At least two notetakers are needed; a primary who would be able to copy his/her notes once a week, and an alternate who would be on standby as a back-up notetaker. The time commitment is minimal, but the difference it makes for the student is significant. DRS pays for the photocopying and will provide a letter of recommendation for your volunteer hours.
If you are interested in volunteering, or if you have any questions, please contact DRS for more information. They are located in Schmitz Hall, room 448. You may call DRS at 543-8924 or email them at [email protected]. Thank you for your consideration."
NOTE TAKER NEEDED
WOOD CHEMISTRY:WOOD CHEMISTRY:“What is wood made “What is wood made
of?”of?”
Wood Macroscopic StructureWood Macroscopic Structure
Outer Bark
CambiumXylem
Phloem
(inner bark)
Heartwood
Sapwood
Pith
Annual Rings
Earlywood
Latewood
Knot
Wood Microscopic StructureWood Microscopic Structure
Imagine that wood is Imagine that wood is made up of millions and made up of millions and millions of toilet paper millions of toilet paper rolls glued together. rolls glued together. These rolls are the fibers These rolls are the fibers that will make paper.that will make paper.
Chemical CompositionChemical Composition ~50% Cellulose~50% Cellulose ~25% Hemicellulose~25% Hemicellulose ~25% Lignin~25% Lignin Variable amounts of Variable amounts of
extractives extractives
3 Main Wood Chemicals3 Main Wood Chemicals
CelluloseCellulose
HemicellulosHemicellulos
eses
LigninLignin
They are all
POLYMERS
What is a polymer?What is a polymer? Polymers are made by Polymers are made by
stringing together a stringing together a bunch of little bunch of little molecules to make a molecules to make a big molecule big molecule
All plastics are All plastics are polymers polymers
Polymers can bePolymers can be linear (long strings) linear (long strings) planar (big sheets)planar (big sheets) three dimensional (like three dimensional (like
lignin)lignin) A bowling ball is one big A bowling ball is one big
three dimensional three dimensional polymerpolymer
Source: World Book Encyclopedia
THE GRADUATE
Images from D. Briggs
Hardwood vs Softwood Fibers
White Pine Red Oak
Fiber StructureFiber Structure
Lumen
Primary
WallMiddle lamella(almost all lignin)
{Secondary
Wall
Woody cells Woody cells consist of consist of several several different layersdifferent layers
The area The area between cells between cells is known as the is known as the middle lamellamiddle lamella
The lignin The lignin content lowers content lowers through the through the cell.cell.
Douglas fir fiber with spiral thickening
How is the cell wall put How is the cell wall put together?together?
Cell wall is assembled by gluing together Cell wall is assembled by gluing together a bunch of very small fibers called a bunch of very small fibers called macrofibrilmacrofibril
Same technology used to produce Same technology used to produce composite materials todaycomposite materials today The glue holding the macrofibrils together is The glue holding the macrofibrils together is
ligninlignin Macrofibrils are made up of microfibrils Macrofibrils are made up of microfibrils
which in turn are made up of cellulose and which in turn are made up of cellulose and hemicellulose polymershemicellulose polymers The glue holding all this together is ligninThe glue holding all this together is lignin
Representation of Cell Wall Representation of Cell Wall ComponentsComponents
Cellulose
Hemicelluloses
Lignin
Wood vs. Rice Krispies Wood vs. Rice Krispies TreatsTreats
Wood Ingredients: Cellulose, Wood Ingredients: Cellulose, Hemicellulose, Lignin, ExtractivesHemicellulose, Lignin, Extractives
Rice Krispies Treats Ingredients: Rice Krispies Treats Ingredients: Rice Krispies, Rice Krispies dust Rice Krispies, Rice Krispies dust (there’s ALWAYS dust in the bag), (there’s ALWAYS dust in the bag), Marshmallows, Butter, some Marshmallows, Butter, some flavoring and preservatives.flavoring and preservatives.
The Perfect RecipeThe Perfect RecipeIngredient Amount Wood Equivalent
Big Rice Krispies 1 3/4 cups Cellulose
Rice Krispies Dust 1 cup Hemicelluloses
Marshmallow 1 1/8 cup Lignin
Butter 3 tablespoons Lignin
Preservatives ~ 1-5 tablespoons Extractives
What is Cellulose?What is Cellulose?
Cellulose is straight Cellulose is straight chain polymer. In bead chain polymer. In bead terms, imagine a very terms, imagine a very very long straight string very long straight string of beads with 2 ends of beads with 2 ends and no branching points.and no branching points.
In wood, cellulose chains In wood, cellulose chains contain typically 10,000 contain typically 10,000 glucose molecules…glucose molecules…quite a long string of quite a long string of beads.beads.
Source: World Book Encyclopedia
Cellulose microfibrils
Microfibril diameter is about 1/100,000 mm
Cellulose For ChemistsCellulose For Chemists Very long straight chain polymer of glucose: Very long straight chain polymer of glucose:
approximately 10,000 in a row in wood. Cotton is approximately 10,000 in a row in wood. Cotton is nearly pure cellulose.nearly pure cellulose.
Cellulose molecules link up in bundles and bundles Cellulose molecules link up in bundles and bundles of bundles and bundles of bundles of bundles to of bundles and bundles of bundles of bundles to make fibersmake fibers
Cellulose forms tight bundles which are very Cellulose forms tight bundles which are very resistant to chemical attackresistant to chemical attack
O
O O
O
O
O
O
O
CH2OH
OHHO
OHHO
CH2OHOH
CH2OH
HO
OH
CH2OH
HO
O
Cellulose
Cellobiose Unit
What are Hemicelluloses?What are Hemicelluloses?
Hemicelluloses are also sugar polymers but Hemicelluloses are also sugar polymers but different from cellulose because they are:different from cellulose because they are: Made up glucose Made up glucose andand other sugars. other sugars. Contain some molecules other than sugars.Contain some molecules other than sugars. Branched little polymersBranched little polymers
The beads have Y’s in themThe beads have Y’s in them Much Much smallersmaller than cellulose as they are made than cellulose as they are made
up of between 50-300 sugars up of between 50-300 sugars There are lots of varieties of hemicelluloses.There are lots of varieties of hemicelluloses. Not very resistant to chemical attack – many Not very resistant to chemical attack – many
easily break down to simple sugarseasily break down to simple sugars
Hemicelluloses for Hemicelluloses for ChemistsChemists
Branched little uncolored sugar polymers (~ 50 Branched little uncolored sugar polymers (~ 50 to 300 sugar units)to 300 sugar units) Composition varies between wood speciesComposition varies between wood species
5 carbon sugars: xylose, arabinose5 carbon sugars: xylose, arabinose 6 carbon sugars: mannose, galactose, glucose6 carbon sugars: mannose, galactose, glucose Uronic Acids: galacturonic acid, glucuronic acidUronic Acids: galacturonic acid, glucuronic acid Acetyl and methoxyl groups (acetic acid & methanol)Acetyl and methoxyl groups (acetic acid & methanol)
O O
O
O
O
O
OH
OHHO
HO
HO OH
OO
O
HO OH
O
O
CO2HH3CO
OHHOH2C
O
O
OH
Cellulose/Hemicellulose Cellulose/Hemicellulose ComparisonComparison
Hemicellulose FragmentHemicellulose Fragment
Folded Cellulose FragmentFolded Cellulose Fragment
What is holding all these fibers What is holding all these fibers together in the tree?together in the tree?
LigninLignin Three dimensional polymerThree dimensional polymer No sugars in itNo sugars in it Nature’s glue – very similar to phenolic Nature’s glue – very similar to phenolic
resin used in plywood. Holds cellulose and resin used in plywood. Holds cellulose and hemicelluloses togetherhemicelluloses together
Second most plentiful natural materialSecond most plentiful natural material Must be removed or weakened to Must be removed or weakened to
separate fibers; turn wood to pulpseparate fibers; turn wood to pulp Dark in nature – especially after reacting Dark in nature – especially after reacting
with alkali – must be de-colored or with alkali – must be de-colored or removed to bleach pulpremoved to bleach pulp
Lignin for ChemistsLignin for Chemists
CH2 O
OH
OCH3
COHH
HC
CH2OH
OH CH2OHC
O
H3CO
C O
CH
CH
H
CH
CHOH2
HO
H
CH
OCH3
OH
C
OH2C
CHO
O
C
CH2OHH3C
O
O
COH
O CH
H3C
CH2OH
H
HCOH
1
2
3
4
5
6
7
H
HC CH
O
O CH
CH2O
C
OCH3
O
CHO
H2C
H3C
8
OHC CH CH2OH
CH2OH
O
O
C
OH
H3C9
10
O
HC CH
COHH2
CH2O
CH
O
OH
H3C
11
H3C
12
HO
CH2OHH3C
13
O
C
O
CH
O CH
O
H3C
H
CH3
CH
OH
O
CH
H3C
CH
H2COH
15
16
Carbohydrate
CH2OH
OH
OCH3
HC 14
H2COH
HC
CHO
17
HOCHO
O
C O CH2
H3C18
HCHO
O
H
H3C
19
O
CH
OCH
O
CH
O
COHH2
OH
OCH3
COHHCOHH2
20
H
CH
H2COH
OCH3
O
HC O
C
OCH3
CH
CH
CHO
22
21
O
H2COHCH2
CH2
H
C O
C
OCH3
24
25
26CH
28
27
O
CH2OH
H
CH3
CH
O
O
H2COH
H
H2COH
H3C
H3C
H2COH
O
CH
CH
OHC
O
O
O
H
23
COH
OCH3
Lignin has been described as 3 dimensional Lignin has been described as 3 dimensional chicken wire.chicken wire.
Picture taken from Katy’s chicken page.
Lignin for non-chemistsLignin for non-chemists
Representation of Cell Wall Representation of Cell Wall ComponentsComponents
Cellulose
Hemicelluloses
Lignin
Representation of Cell Wall Representation of Cell Wall ComponentsComponents
ExtractivesExtractives The term extractives refers to a group of unique The term extractives refers to a group of unique
chemical compounds which can be removed from plant chemical compounds which can be removed from plant materials through extraction with various solventsmaterials through extraction with various solvents
Typically these chemicals constitute only a small Typically these chemicals constitute only a small portion of the tree (<5%)portion of the tree (<5%) In some tropical species this can be as high as 25%In some tropical species this can be as high as 25%
Extractives are produced by plants for a variety of usesExtractives are produced by plants for a variety of uses The most common is protectionThe most common is protection
Extractives can cause serious problems for processingExtractives can cause serious problems for processing Pitch is a term which is often used when describing Pitch is a term which is often used when describing
some groups of extractives some groups of extractives Extractives are responsible for the characteristic color Extractives are responsible for the characteristic color
and odor of woodand odor of wood
Chemical Composition of Chemical Composition of Wood: HardwoodsWood: Hardwoods
0
10
20
30
40
50
60
%
Red Maple EnglishOak
Iroko Balsa
Cellulose*
Hemicellulose*
Lignin*
Extractives
* Data for Cellulose, Hemicellulose & Lignin on extractive free wood basis
Chemical Composition of Chemical Composition of Wood: SoftwoodsWood: Softwoods
05101520253035404550
%
Douglas Fir Redwood Yellow Pine Balsam Fir
Cellulose*Hemicellulose*Lignin*Extractives
* Data for Cellulose, Hemicellulose & Lignin on extractive free wood basis