Английский язык. Учебные задания. Циленко Л.П. - 9 стр.

UptoLike

ВУЗ: 

ТГТУ | Тамбов

Составители: 

Рубрика: 

Пояснения к тексту
1. condensation – уплотнение
2. gradual – постепенный
3. elimination – устранение, исключение, очищение
4. to derive – извлекать
5. excessive – излишний, чрезмерный
Principles and process of polymerization in plastics production
1. Condensation polymerization and addition polymerization are the two main processes in plastics produc-
tion. The manufacture of plastics depends upon the building of chains and networks during polymerization. A
condensation polymer is formed by a synthesis that involves the gradual reaction of reactive molecules with one
another, with the elimination of small molecules such as water. The reaction gradually slows down as polymers
are built up.
2. An addition polymer forms chains by the linking of small identical units without elimination of small
molecules. The most important concept in condensation polymers is that of "functionality", i.e., the number of
reactive groups in each molecule participating in the chain build-up. Each molecule must have at least two reac-
tive groups, of which hydroxyl (–OH), acidic endings (–COOH), and amine endings (–NH) are the simplest.
3. Hydroxyl is characteristic of alcohol endings, combining with an acid ending to give an ester, the poly-
mer being known as a polyester. Examples are polyethylene terephthalate obtained by reaction of ethylene gly-
col containing hydroxyl groups at each end and terephthalic acid containing two acidic groups and polycarbon-
ate resins.
4. Alcohols are a particular class of oxygen-containing chemical compounds with a structure analogous to
ethyl alcohol (C–HOH). Amines are various compounds derived from ammonia by replacement of hydrogen by
one or more hydrocarbon radicals (molecular groups that act as a unit). Esters are compounds formed by the
reaction between an acid and an alcohol or phenol with the elimination of water.
5. Bulk addition polymerization of pure monomers is mainly confined to styrene and methyl methacrylate.
The process is highly exothermic, or heat producing. The dissipation of heat (necessary to maintain chain
length) is achieved in the case of styrene by intensive stirring of the viscous, partially polymerized mixture,
which is then passed down a tower through zones of increasing temperature. Alternatively, polymerization may
be completed in containers that are small enough to avoid an excessive temperature rise as a result of the heat
released during polymerization.
V. Прочитайте пятый абзац текста и ответьте письменно на следующий вопрос:
How does polymerization may be completed аlternatively?
ВАРИАНТ IV
I. Перепишите и письменно переведите на русский язык следующие предложения. Помните, что
объектный и субъектный инфинитивные обороты соответствуют придаточным предложениям (см. обра-
зец выполнения I).
1. Our country is known to have put the first atomic power station into operation in 1954.
2. The early artificial satellites showed the Earth to be surrounded by intense radiation.
3. On some occasions scientists may consider the acceleration of gravity to be constant.

Страницы