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

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

Woody Plants Trees Shrubs Wood lianas – climbing woody vines

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

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

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

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

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

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

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

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

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

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

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