Timber. Wood formation. Wood structure. Нeat conductivity of wood

Timber.

Timber is one of the most important materials used in all branches of industry. Most of the houses in which we live are partly built of timber: they all have wooden floors, wooden doors and wooden window frames.

Artificial textiles are manufactured from cellulose, a substance produced from the woody fiber of plants. Several medicines are obtained from different trees whose medicinal nature is widely known to modern chemists.

Timber was widely used for construction purposes and home needs in prehistoric times. We are told by archeologists that things made of wood were used over 3,500 years ago. Timber was referred   to as the best   structural material by the Greeks and Romans.

A scientific study of the properties and qualities of wood was started only at the beginning of the 18-th century. The first researches were devoted to the study of the strength of timber. As a result, a considerable amount of data was collected giving an idea of the properties of different kinds of timber. The research workers paid much attention to studying the conditions of the growth of the tree. The connection between the mechanical properties and the structure of timber was established and proved.

Wood as a fibrous material for making pulp was first used more than a century ago. This fibrous material being available in large quantities, broad possibilities were opened for increasing the manufacture of pulp. We know pulp to be widely used for producing paper and for making different kinds of artificial fibres .

It should be noted that timber grows in importance. The production of hard and strong fibre -boards out of sawdust mixed with mineral substances is the achievement of modern research work.

Different species of wood are used for the manufacture of pulp. Some years ago spruce was the chief source of pulp manufacture. Now for this purpose pine is used alongside with spruce. Moreover, about 20% of the pulp is supplied by the hardwoods.

Exercises.

Ex.1: Translate the following words and remember them, artificial, fibre, to connect, pulp, sawdust, fibre - board, spruce.

Ex.2: Translate the words given below, paying attention to different suffixes and prefixes: Wood, woody,   wooden; differ, different, difference, differently;   wide, widely, width, widen;   science, scientific, scientist;    grow, growth;    fibre, fibrous;    part,    partly; connect,    connection, connecting; important, importance;    produce,    production, product;    historic, prehistoric;    structure, structural; possible, possibility, impossible, impossibility.

Ex.3: State the part of speech of the underlined words and translate the sentences.

1.   Timber is one of the most important materials.

2.   Timber was widely used for construction purposes in prehistoric times.

3.   We   know   pulp   to   be   widely used   for   production of  paper   and different kinds of  artificial fibbers.

4.   A scientific study of the strength of timber was started at the beginning of the 18-th century.

5.   Wood   is valuable   raw material for different branches of  industry   such   as construction, making cooking utensils and manufacture of furniture.

Ex.4: Answer the following questions.

1.   Why do we consider timber one of the most important raw materials?

2.   What are the artificial textiles manufactured from?

3.   Can medicines be obtained from trees?

4.   Was timber used in prehistoric times?

5.   When was a scientific study of wood started?

6.   What material is used for making pulp?

7.   Is there any possibility to turn sawdust into valuable products?

8.   Was spruce the chief source of pulp manufacture some years ago?

9.   What species of wood are used for the manufacture of pulp now?

10. How many per cent of pulp is supplied by the hardwoods?

Wood formation.

Wood is a fascinating natural material to use, study and admire. From the very earliest times man has used wood for tools and weapons, buildings, furniture, or just as fuel for his fires. Nowadays wood serves very many purposes too. As a matter of fact, it is adaptable to both structural and decorative use.

But it is impossible to use valuable qualities of wood without gaining some knowledge of the structure and chemical composition of this material. Being a representative of the woody plants a tree has three main parts: roots, a stem and leaves.

A stem or a trunk is considered to be of the greatest value in the manufacture of wood products. The trunk has an outer covering called the bark which protects the wood from extremes of temperature, mechanical injury and harmful fungi and insects.

Between the bark and the wood there is a thin delicate tissue known as the cambium. This tissue produces both the bark and the wood. The enlargement of the trunk in girth is brought about entirely by the activity of the cambium.

The production of wood and bark tissue occurs only when the cambium is growing. In temperate regions this occurs during the spring and summer months. During this period of time leaves in the tree's crown have to work hard . They are winning carbon compounds the wood is composed of.

The roots are working hard as well. To supply the tree with mineral salts needed for its life, processes the roots are carefully exploring the soil under the tree. All this time sap is actively flowing from the roots up the stem.

No  wood   is  formed   during   autumn  when  the  rhythm   of growth   slows   down, nor  in  winter when the tree rests. Many trees, of course, are leafless at that time of the year. New cells produced due to the activity of the cambium form layers of wood called sapwood . The function of sapwood is to carry sap. A tree getting older, slow chemical changes take place in its inner layers. As a result, sapwood is turned into heartwood.

Heartwood is harder and stronger than sapwood . In the majority of timbers heartwood is more resistant to decay. Therefore it is desirable to exclude the use of sapwood in situations where the likelihood of fungi infection is considerable.

Exercises.

Ex.1: Translate the following words and remember them.

structure, manufacture, bark, insect, layer, sapwood, heartwood, hard, fungi, occur.

Ex.2: Translate the words given below, paying attention to different suffixes and prefixes: possible, possibility, impossible, impossibility; value, valuable, valueless; chemistry, chemist, chemical; compose, composition;    large, enlarge, enlargement;    act, active, actively, activity;    care, careful, carefully, careless; leaf-leafless; transform, formation, transformation; decorate, decorative, decorator ; harm - harmful.

Ex.3: State the part of speech of the underlined words and translate the sentences.

1.   Wood is a very important raw material adaptable to both structural and decorative use.

2.    The enlargement of the trunk is brought about entirely by the activity of cambium.

3.   No wood is formed in autumn and   in winter when the growth of trees slows down and they are leafless.

4.   It is impossible to use valuable qualities of wood without studying the structure and chemical composition of this material.

Ex. 4: Answer the following questions.

1.   What purposes did ancient people use wood for?

2.   Does wood serve many purposes nowadays?

3.   What part of the tree is of the greatest value in the manufacture of wood products?