Plastic

The construction industry uses over a quarter of all the plastics that are produced. However of the large number of plastics available, only a small number are suitable for use in the major elements of a building. The principal distinction among plastics is between the thermosetting and thermoplastic materials. Both types may be reinforced by fibres and in the case of thermosetting plastics this is almost always necessary in order to obtain good mechanical properties. Plastics are widely used because of their high strength to weight ratio, their ease of forming and their resistance to corrosion.

The most popular thermosetting plastic in use in the construction industry, due to its cost, strength, relative hardness and toughness, is fibreglass reinforced polyester, GRP, a composite which has a polyester resin matrix and glass fibre reinforcement. In a reinforced plastic the matrix binds the fibres together and protects them from damage; the fibres are much stronger than the surrounding matrix material. Fillers such as glass, mica and sand can also be incorporated so as to improve properties.

The properties of the plastic depend on the molecular structure and on the way the links between molecules are made. Only variations in temperature are needed in order to make large changes in the properties of the plastic. For example, unlike most metals, an increase in temperature even of 10°C (18°F) has a major effect on the strength, creep, elastic modulus and, therefore, the stiffness of the plastic. In addition to temperature, the mechanical properties of a plastic will depend on its conditions of use since production.

Notes:

fibreglass reinforced polyester полиэфирное стекловолокно

matrix n. матрица

mica n. слюда

molecular adj. молекулярный

thermoplastic adj. термопластичный

thermosetting adj. термореактивный

toughness n. жёсткость, прочность

Ответьте на вопросы к тексту.

1. How many plastics does the construction industry use?

2. What is the principal distinction among plastics?

3. Why are plastics widely used?

4. What is the most popular plastic?

5. How can the properties of plastics be improved?

6. What do the properties of the plastic depend on?

7. What is needed in order to change the properties of the plastic?

8. What has a major effect on the stiffness of the plastic?

9. How high should an increase in temperate be?

10. What will the mechanical properties of a plastic depend on?

Date: 2016-02-19; view: 481; Нарушение авторских прав