Wood and its derivatives

Wood and its derivatives

Before starting the unit, we will watch a video about building wooden bridges:

In this video we can find a great amount of vocabulary related to this unit.
During class we translated the words. Do you remember?
Design Building Wooden Arch Bridge Tools
Crafts Skill Hammer Row
Timber Axes Saws Cranes

 

Wood and its derivatives

Wood:

1. Raw vegetable material.

2. It comes from the trucks of trees and bushes.

3. It’s composed of cellulose fibres and lignin.

Properties of wood

1. Physical properties

a. Hardness. It’s hard, but you can work with nails and screws in it.

b. Density. The wood has a density less than 1 g/cm3, so that floats in water.

c. Electrical insulation.

d. Thermal insulation. But be careful, as the wood burns beginning 300 °C.

e. Porosity. Wood has tiny holes, called pores.

f. Mechanical resistance. Wood has good mechanical resistance (traction, compression and bending).

g. Colour and grain. Wood is lovely.

2. Ecological properties.

a. Renewable. Re – new –able. Can be regenerated.

b. Biodegradable. Bio –degrade– able. It decomposes naturally.

c. Recyclable. Re – cycle–able. You can return it to the productive cycle.

How to process wood

1. Cutting and pruning (the trunks).

2. Transport (the trunks).

3. Removing the bark (from the trunks).

4. Sawing (the trunks into plank). We cut the wood as we want to use it later.

5. Washing. We need to remove unwanted wood fluids.

6. Drying. There are three drying methods:

a. Natural drying. The planks are put in piles, out of the rain and direct sun, with spaces between them so that the air can
circulate. This is a slow process.

b. Artificial drying. The wood is dried in big rooms (dryers) with hot, dry air. This system is quicker and more efficient.

c. Mixed drying. This is a combination of the two methods. First, natural drying is used until the humidity of the wood reaches about 20%, then artificial drying for the last phase.

7. Planing. To make the wood smooth.

8. Warping. If you do not dry properly the wood it may be deformed in different ways.

 

Classifying wood

Wood is classified as hardwood or softwood depending on the tree it comes from.

1. Hardwood

a. Deciduous trees.

b. They grow slowly and have thick trunks.

c. They contain little resin.

d. They are compact and resistant, the can be different colours.

e. Types of hardwood trees: beech, oak, cherry, mahogany

f. Uses: furniture, doors, windows, scientific and musical instruments.

2. Softwood

a. Conifers.

b. They grow quickly.

c. They are light and easy to work with because they are less resistant.

d. Types of softwood trees: pine, white/red fir, white poplar

e. Uses: furniture, boats, building, plywood.

Prefabricate wood

In videos of the process of obtaining wood tables we have seen the amount of wood that is wasted. That remaining wood, and what we obtain from recycling, is used to make prefabricated pieces.

1. Advantages:

a. Easy to work with.

b. A lot of sizes and finishes.

c. Not attacked by parasites.

d. Helps protect the environment.

e. Cheaper.

2. Types:

Playwood Chipboard
Thin sheets of wood glued together and compressed.  Very sensitive to humidity and temperature changes. Made with wood chips glued together (90% chips and 10% glue). Fragile, not easily deformed and increase in volume from water absorption.

 

 

Cellulose materials

 

The most important cellulose materials is paper. The next illustration shows the process of paper making.

1. Cut trees into trunks.

2. Remove the bark.

3. Grind the wood.

4. Make cellulose paste.

5. Wash and bleach the cellulose paste.

6. Liquid paste.

7. Press with rollers.

8. Suction to removewater.

9. Smooth with rollers.

10. Dray with hot rollers.

11. Roll up and cut.

 

 

Volver al inicio de la página

 

Deja un comentario

Tu dirección de correo electrónico no será publicada. Los campos obligatorios están marcados con *