Wood and Textile Properties: Characteristics and Uses
Wood: Properties, Procurement, and Classification
Properties of Wood
Color: The most striking property. Wood can be stained or painted.
Weight: Depends on moisture and density. The actual density of wood is approximately equal for all species, about 1.56. Apparent density varies not only from one species to another but even within the same tree, depending on moisture and the location within the tree. To find the average density of a tree, it is necessary to take samples from several sites. As the bulk density includes the volume of holes and clumps, the higher the bulk density of timber, the larger the surface of its resistance elements and the smaller the pores. Woods are classified by their bulk density: heavier (if greater than 0.8), light (if between 0.5 and 0.7), and lightweight (under 0.5).
Shrinkage and Swelling: Wood changes volume according to its moisture content. The concentration is higher in the sapwood than in the heartwood (sapwood is from the outside; heartwood is from within). Swelling occurs when wood absorbs moisture.
Hardness: The hardness of wood is its resistance to wear, scratching, and nailing. Woods are classified as very hard, hard, somewhat hard, soft, and very soft.
Cut Resistance: Wood offers resistance against a force that tends to break off or cut it into two parts.
Cleavability: Ease of cracking and the ability of wood to split in the longitudinal direction under the action of a wedge.
Flexibility: The property that allows some wood to be bent or curved in its longitudinal direction without breaking.
Elasticity or Deformability: When the yield limit is exceeded, timber behaves as a plastic body, and permanent deformation occurs.
Conductivity: Dry wood is a bad conductor of heat and electricity, but when wet, the reverse is true.
Thermal Expansion:
Length: Varies greatly depending on the species, dryness, and moisture content.
Wear: Timber subjected to friction or erosion experiences a loss of material.
Procurement of Wood
Forestry and Logging Processes: Forestry is the care of forests oriented to obtain the maximum sustained yield of resources and benefits. There are two types of logging:
- Partial Logging: Dividing the forest into plots to operate a rotating felling depending on the growth cycle of the species.
- Plantation Logging: Cutting down trees to grow new trees from seeds that reach maturity rapidly.
Methods of Selective Logging: Trees are cut down by size and quality from all areas of the forest. Trees should be felled in autumn when there is the least sap circulation.
Transport: The second phase, where the wood is transported from the place of cutting to the sawmill.
Debarking: Separating the bark from the wood while branches are removed from the trunk. The bark can be used as raw material.
Drying: The most important process for ensuring quality timber. Types of drying include:
- Natural Drying: Logs are placed in piles separated from the soil, allowing air to circulate between them, and protected from water.
- Artificial Drying:
- Immersion Drying: The tree is placed in a pool, and water is used to push out the sap from one side, drying the tree much faster.
- Vacuum Drying: A safer process where logs are introduced into vacuum machines.
- Vaporization Drying: A somewhat expensive method where timber is placed on a ship at a certain height from the ground, where a cloud of steam at 80 to 100ºC circulates.
- Mixed Drying:
- Heat Pump Drying: An extension of spray drying, but with a heat pump, outside air is not needed.
Classification of Wood
Softwoods: Mainly conifers. These trees are tall with a spiky tip, fast-growing, and have low population density, resulting in long, straight trunks.
Hardwoods: Slow-growing with higher density. These are other types of trees, but only some are used for commercial purposes.
Derivatives of Wood
Artificial boards (plywood, particle board, and fiberboard), cardboard, paper, recycled paper.
Textile Fabrics
Animal Fibers
Silk: Obtained through a larva that weaves the fiber through its diet of brown leaves.
Wool: The most valuable wool comes from sheep between three and six years old. A sheep can produce about 3 kg of fine wool and 2-6 kg of thick wool annually.
Plant Fibers
Cotton: Obtained from plants that were planted many years ago.
Linen: Comes from the flax plant, where the stem is removed for textile fiber.