1. Definition
Wood is a plant but not all plants possess woody stems and not all that have woody stems are suitable for papermaking

2. Woody Plants are Vascular
Specialized conducting tissue
xylem (wood)
phloem (inner bark)
Perenial – live for years
Stem persists from year to year
Secondary thickening of stem
activity of growing layer - cambium

3. Woody Plants
Trees
Shrubs
Wood lianas – climbing woody vines

4. Non-woody’s in paper Hemp Bamboo Mulberry China grass Abaca Flax Kenaf
Jute
Papyrus
Esparto
Rice Straw etc

5. All Wood Tree stems - vertical arrangement Cellular - carbohydrates
Cellulose
Noncellulosic
Lignin
Anistropic
Three major directional axis
Hygroscopic
Loses and gains water – humidity/temperature

6. Characteristics of Wood
Ease to be worked
Ease to be fastened
Insulation properties – heat/sound/electrical
No rusting nor crystallization
Excellent shock & vibration resistance
Flexural rigidity
High stiffness to weight ratio
Converted into
Paper, plastics, rayon, vanillin, ethyl alcohol, charcoal

7. Characteristics of Wood
Uneven dimensional changes
Combustible but changed/controlled
Variability of strength
Ravages of fungi and insects

8. Lumber Producing Trees
Spermatophytes
Gymnosperms
Coniferales (softwoods)
Pines, firs, spruce, cedar, redwood, hemlock, bald cypress etc
Angiosperms
Dicotyledons (palm trees, bamboo, yuccas are monocotyledon)
Hardwoods
Ring Porous (non uniform pores)
chestnut, oak, elm, black locust, ash
Diffuse porous (seasonal growth)
maple, birch, gums, yellow poplar
The different types of wood species
Different variations in characteristics
Gymnosperm – naked seed, Angiosperm seed in a vessel

9. Young Tree Epidermis Cortex Phloem Cambium Xylem Pith
Secondary Thickening
Periderm
Primary &Secondary phloem
Primary & Secondary xylem
Draw a picture

10. Older Tree Outer Bark Inner Bark Cambium Layer Sapwood
Storage of food, transport of water/sap
Changes to heartwood – extractive content
Heartwood (inactive cells)
Pith

11. Growth of a Tree Spring Summer Ring Width Porous Low in density
Early wood
Summer
Denser
Darker
Late wood
Ring Width
Discontinuous
False rings – effect age estimates

12. Wood Plant Cell Cell Wall Other Parts Primary Wall Secondary Wall
Bundled microfibrils
Secondary Wall
S1 – outer
Different oriented microfibril bundles
Tracheids
S2 – central
Dense organization of lamellae
Aggregation of cellulose
S3 – inner
Very flat
Warty Layer
Other Parts
Vessel Elements
Parenchyma cells – storage tissue
Epithelial cells – resin or gum canal

13. Chemical Composition of the Cell Wall
Primary
Cellulose (40-50%)
Long chain polymer
Low solubility
Hemicellulose (20-35%)
Polysaccharides
Lignin (15-35%)
Inhibits water
Secondary
Extractives – odor, color, decay, insect resistance
Tannins
Volatile Oils and Resins
Gums and latex
Ash

14. Physical Nature of Wood
Effects on Fibers
Moisture Content
Shrinkage
Specific Gravity