Types of plastics

Epoxy resin is a thermoset plastic containing epoxy groups. Epoxy resin hardens when it is mixed with solidifier and plasticizer. Plasticizers make a polymer more flexible.

Epoxy resins have outstanding adhesion, toughness, and resistance to attack from chemicals. They form strong bonds and have excellent electrical insulation properties. Large, complex, void-free castings can be made from them. They are also used as adhesives, and in composites for boat building and sports equipment.

PVC (polyvinyl chloride) is a thermoplastic polymer made from vinyl chloride is a colourless solid with outstanding resistance to water, alcohols, and concentrated acids and alkalis. It is obtainable as granules, solutions, lattices, and pastes. When compounded with plasticizers, it yields a flexible material more durable than rubber. It is widely used for cable and wire insulation, in chemical plants, and in the manufacture of protective garments. Blow moulding of unplasticized PVC produces clear, tough bottles which do not affect the flavour of their contents. PVC is also used for production of tubes or pipes.

Polystyrene is a thermoplastic produced by the polymerization of styrene. The electrical insulating properties of polystyrene are outstandingly good and it is relatively unaffected by water. Typical applications include light fixtures, toys, bottles, lenses, capacitor dielectrics, medical syringes, and light-duty industrial components. Extruded sheets of polystyrene are widely used for packaging, envelope windows, and photographic film. Its resistance to impact can be improved by the addition of rubber modifiers. Polystyrene can be readily foamed; the resulting foamed polystyrene is used extensively for packaging.

Polythene (polyethene, polyethylene) is a plastic made from ethane. It is one of the most widely used important thermoplastic polymers. It was first developed by the polymerization of ethane at a pressure of 2,000 bars at 200 ºC. This produced low-density polythene (LDPE). A relatively high-density form (HDPE) was synthesized in the 1950 s using a complex catalyst. Polythene is a white waxy solid with very low density, reasonable strength and toughness, but low stiffness. It is easily moulded and has a wide range of uses in containers, packaging, pipes, coatings, and insulation.

3. Make up the plan of the text.

4. Give a brief summary of the text.

Text D

1. Read the text and choose the most suitable title out of the given once:

a) Advanced Composites.

b) Composit Materials.

c) Composites.

The combinations of two or more different materials are called composite materials. They usually have unique mechanical and physical properties because they combine the best properties of different materials. For example, a fibre-glass reinforced plastic combines the high strength of thin glass fibres with the ductility and chemical resistance of plastic. Nowadays composites are being used for structures such as bridges, boat-building etc.

Composite materials usually consist of synthetic fibres within a matrix, a material that surrounds and is tightly bound to the fibres. The most widely used type of composite material is polymer matrix composites (PMCs). PMCs consist of fibres made of a ceramic material such as carbon or glass embedded in a plastic matrix. Usually the fibres make up about 60 per cent by volume. Composites with metal matrices or ceramic matrices are called metal matrix composites (MMCs) and ceramic matrix composites (CMCs), respectively.

Continuous-fibre composites are generally required for structural applications. The specific strength (strength-to-density ratio) and specific stiffness (elastic modulus-to-density ratio) of continuous carbon fibre PMCs, for example, can be better than metal al1oys have. Composites can also have other attractive properties, such as high thermal or electrical conductivity and a low coefficient of thermal expansion.

Although composite materials have certain advantages over conventional materials, composites also have some disadvantages. For example, PMCs and other composite materials tend to be highly anisotropic – that is, their strength, stiffness, and other engineering properties are different depending on the orientation of the composite material. For example, if a PMC is fabricated so that all the fibres are lined up parallel to one another, then the PMC will be very stiff in the direction parallel to the fibres, but not stiff in the perpendicular direction. The designer who uses composite materials in structures subjected to multidirectional forces, must take these anisotropic properties into account. Also, forming strong connections between separate composite material components is difficult.

The advanced composites have high manufacturing costs. Fabricating composite materials is a complex process. However, new manufacturing techniques are developed. It will become possible to produce composite materials at higher volumes and at a lower cost than is now possible, accelerating the wider exploitation of these materials.

2. Write out:

a) key worlds and terms;

b) the sentences expressing the main idea of each paragraph.

Unit 8

GRAMMAR: Modal Verbs

1. a) Translate the following words, word combinations and chemical terms into Russian:

butadiene, dimensional, flexural, opaque, polystyrene, rigidity, subsequent, toughness, unique, versatile, based on the first letters, with essentially no loss, sediment, substitute, residue

b) Translate the following derivatives into Russian:

1) develop, development; 2) compose, composition; 3) mono-mer, monomeric; 4) adopt, adoptation; 5) polymer, copolymer, polymerization, polymerize; 6) nature, natural; 7) improve, improvement; 8) tough, toughness; 9) introduce, introduction; 10) rigid, rigidity; 11) resist, resistant, resistance; 12) apply, application; 13) viscous, viscosity; 14) use, useful, useless; 15) process, processing.

c) Translate into Russian paying attention to the Modal Verbs:

1. Plastics can do a better job, often at lower cost.

2. The development of lamination has shown how modern plastics may be used for many engineering and structural applications.

3. We are able to build car bodies and the hulls of the boats from plastics.

4. We shall have to seek new sources of organic chemical materials.

5. The present century is the time when one has to understand how to make all the new synthetic materials from simple chemicals.

6. We can make alcohol by fermentation of the sugars produced by fast-growing plants.

7. One has to keep in mind that the most striking property of the white phosphorus is its activity with oxygen.

8. They have to determine this substance.

9. Adhesion should not be confused with friction.

10. Coal and petroleum are capital assets; the world has a limited supply, and we cannot replace the material we use.

2. Put the words in the correct order to form sentences.

1) can be, remelted, and, with, essentially, no, in, properties, ABS plastics, various, loss, reformed, into, shapes;

2) have ousted, plastics, they, do, job, often, at lower cost, materials, can, a better, older, because;

3) plastics, may, be, for, many, and, structural, modern, used, engineering, applications;

4) we, make, by, the, sugars, produced by, fast-growing, plants, can, alcohol, of, fermentation;

5) are, build, car, and, the hulls, the, boats, of, plastics, able to, bodies, from, we.