I. Text A: «Plastics», Text B: «Types of plastics», Text C: «Composite Materials»

II. Famous People of Science: Alfred Bernhard Nobel.

Text A: «PLASTICS»

Plastics are non-metallic, synthetic, carbon-based materials. They can be moulded, shaped, or extruded into flexible sheets, films, or fibres. Plastics are synthetic polymers. Polymers consist of long- chain mole­cules made of large numbers of identical small molecules (monomers). The chemical nature of a plastic is defined by the monomer (repeating unit) that makes up the chain of the polymer. Polyethene is a polyolefin; its monomer unit is ethene (formerly called ethylene). Other catego­ries are acrylics (such as polymethylmethacrylate), styrenes (such as polystyrene), vinys (such as polyvinyl chloride (PVC)), polyes­ters, polyurethanes, polyamides (such as nylons), polyethers, acetals, phenolics, cellulosics, and amino resins. The molecules can be either natural — like cellulose, wax, and natural rubber — or synthetic — in polyethene and nylon. In co-polymers, more than one monomer is used.

The giant molecules of which polymers consist may be linear, branched, or cross-linked, depending on the plastic. Linear and branched molecules are thermoplas­tic (soften when heated), whereas cross-linked molecules are thermosetting (harden when heated).

Most plastics are synthesized from organic chemicals or from natural gas or coal. Plastics are light-weight com­pared to metals and are good electrical insulators. The best insulators now are epoxy resins and teflon. Teflon or polytetrafluoroethene (PTFE) was first made in 1938 and was produced commercially in 1950.

Plastics can be classified into several broad types.

1. Thermoplastics soften on heating, then harden again when cooled. Thermoplastic molecules are also coiled and because of this they are flexible and easily stretched.

Typical example of thermoplastics is polystyrene. Polystyrene resins are characterized by high resistance to chemical and mechanical stresses at low temperatures and by very low absorption of water. These properties make the polystyrenes especially suit­able for radio-frequency insulation and for parts used at low temperatures in refrigerators and in airplanes. PET (polyethene terephthalate) is a transparent thermoplas­tic used for soft-drinks bottles. Thermoplastics are also viscoelastic, that is, they flow (creep) under stress. Ex­amples are polythene, polystyrene and PVC.

2. Thermosetting plastics (thermosets) do not soften when heated, and with strong heating they decompose. In most thermosets final cross-linking, which fixes the molecules, takes place after the plastic has already been formed.

Thermosetting plastics have a higher density than thermoplastics. They are less flexible, more difficult to stretch, and are less subjected to creep. Examples of ther­mosetting plastics include urea-formaldehyde or polyurethane and epoxy resins, most polyesters, and phenolic polymers such as phenol-formaldehyde resin.

3. Elastomers are similar to thermoplastics but have sufficient cross-linking between molecules to prevent stretching and creep.

Vocabulary:

carbon — углерод

flexible — гибкий

fibre — волокно, нить

chain — цепь

identical — одинаковый, идентичный

molecule — молекула

branch — разветвленный

to synthesize — синтезировать

chemicals — химические вещества

to soften — смягчать

cellulose — клетчатка, целлюлоза

wax — воск

thermosetting plastics — термореактивные пласт­массы

to harden — делать твердым

coil — спираль

stretched — растянутый

transparent — прозрачный

rubber — резина, каучук

to decompose — разлагаться

soft-drink — безалкогольный напиток

to subject — подвергать

polyurethane — полиуретан

resin — смола

similar — сходный, подобный

sufficient — достаточный

to prevent — предотвращать

General understanding

1. What is the definition of plastics?

2. What is the basic chemical element in plastics for­mula?

3. What do polymers consist of?

4. What are long-chain molecules made of?

5. What are the main types of polymers?

6. Give examples of plastics belonging to these types.

7. What plastics are the best electrical insulators?

8. Describe the difference between thermoplastics and thermosets.

9. What are the main types of structures of polymers?

10. What are the most important properties of plastics?

11. Give the examples of various uses of plastics be­cause of their characteristic properties.

 

Exercise 5.1. Find English equivalents in the text:

1. синтетические полимеры

2. молекулы с длинными цепями

3. характерные свойства полимера

4. синтезируются из органических химических ве­ществ

5. хороший электрический изолятор

6. размягчаться при нагревании

7. затвердевать при охлаждении

8. гибкий и легко растяжимый

9. течь под нагрузкой

10. более высокая плотность

11. менее подвержены ползучести

12. достаточная взаимосвязь между молекулами

Exercise 5.2. Translate into English:

1. Длинные цепи молекул полимеров состоят из одинаковых небольших молекул мономеров.

2. Сополимеры состоят из двух и более мономеров.

3. Пластмассы можно получать в виде листов, тон­ких пленок, волокон или гранул.

4. Молекулы полимеров могут быть линейными, ветвящимися или с поперечными связями.

5. Малый вес пластмасс и хорошие электроизоля­ционные свойства позволяют использовать их в радио­электронике и электроприборах, а также вместо ме­таллов.

6. Молекулы термопластов имеют извитую форму и, поэтому, они гибкие и легко растяжимы.

7. Эластомеры имеют большое число поперечных связей между молекулами.

Text В: «TYPES OF PLASTICS»

Epoxy resin.

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.

2. PVC (polyvinyl chloride)

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.

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.

4. Polythene (polyethene, polyethylene)

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 bar at 200°C. This produced low-density poly­thene (LDPE). A relatively high-density form (HDPE) was synthesized in the 1950s 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.

Vocabulary:

adhesion — прилипание

adhesive — клей

bond — связи, узы

insulation — изоляция

casting — литье

void — пустота

solid — твердое тело, твердый

acid — кислота

alkali — щелочь

to obtain — доставать, получать

granule — гранула

solution — раствор

lattices — латексы

paste — паста

yield — выход

durable — прочный

rubber — резина, каучук

garment — предметы одежды

lens —линза

capacitor — эл. конденсатор

syringe — шприц

light-duty — неответственный

envelope — зд. обрамление

impact — удар

improved — улучшенный

modifiers — модификаторы

addition — добавление

readily — легко, с готовностью

foam — пена

catalyst — катализатор

wax — воск

reasonable — приемлемый, неплохой

coating — слой, покрытие

General understanding:

1. What are the types of plastics?

2. What are the features of the epoxy resin?

3. What is epoxy resin used for?

4. What is PVC usually used for?

5. What are the typical applications of polystyrene?

6. When was polyethylen synthesized?

7. Under what conditions is polyethylen synthesized?

8. What sorts of polyethylen can be synthesized?

Exercise 5.3. Translate into Russian:

1. Polythene is a plastic made from ethane.

2. Epoxy resins have outstanding adhesion, toughness and resistance to attack from chemicals.

3. PVC is a colourless solid with outstanding resist­ance to water, alcohols, and concentrated acids and al­kalis.

4. Polystyrene is a thermoplastic produced by the po­lymerization of styrene.

5. Polythene is a white waxy solid with very low den­sity, reasonable strength and toughness but low stiffness.

Exercise 5.4. Translate into English:

1. Эпоксидная смола затвердевает когда смешива­ется с отвердителем и пластификатором.

2. Эпоксидные смолы используются в качестве клея, а с добавками — в строительстве лодок и спор­тивного снаряжения.

3. ПВХ — бесцветное твердое вещество с выдаю­щейся устойчивостью к воздействию воды, спиртов, концентрированных кислот и щелочей.

4. ПВХ широко используется при производстве изоляции для проводов.

5. Выдувка непластифицированного ПВХ исполь­зуется при производстве прозрачных бутылок для на­питков.

6. Полистирол легко вспенивается и используется для упаковки.

7. Полиэтилен — воскообразное вещество белого цвета с очень низкой плотностью и малой жесткостью.