Texts on specialities
New words and word-combinations to be remembered:
rubber гума, каучук
to possess володіти, мати
resistant стійкий, витривалий
inexpensive дешевий, недорогой
long-lived durability витривалість
to compete with конкурувати з
chain reaction ланцюгова реакція
to mold формувати під тиском
Life depends fundamentally on organic polymers. These polymers provide not only food but also clothing, shelter and transportation.
Indeed, nearly all the material needs of man could be supplied by natural organic products. The list of these materials and things made of them might be very long: wood, fur, leather, wool, cotton, silk, rubber, oils, paper, paints and so on. The organic polymers from which such things could be made include proteins, cellulose, starch, resins and few other classes of compounds.
Modem methods of physical and chemical analyses have uncovered the principles that govern the properties of the natural polymers. A new industry of man-made organic polymers has appeared. One could list the principal products such as fibres, synthetic rubbers, coating, adhesive and a lot of materials called «plastics». Plastics and synthetic are already in common use.
Synthetic polymers now available already posses several of the properies required in a structural material. They are light in weight, transported, easily repaired, highly resistant to corrosion and solvents, and satisfactory resistant to moisture. It would be necessary to add that they have long-lived durability and resistance to high temperatures,.A very important question could arise whether synthetic polymers could be made inexpensive enough to compete with the structural materials such as metals and ceramics. The answer could be: «yes».
Natural substances can’t be like polymers in lightness, strength, chemical durability, ability to absorb vibrations and reflect, stop or let through sound or radio waves or nuclear radiation. Polymers can be elther porous or monolithic, transparent or opaque. They have long been used as excellent electrical insulators.
It might seem odd that man came rather late to the investigation of organic polymers as the principal means of supporting life. The natural polymers such as proteins, cellulose and others dominated his existence and even in ancient times people used these materials.
It was only in the 20th century that the scientists began thorough investigation of these materials. Having used some powerful physical Instruments, an electron microscope, viscometer, X-ray-diffraction apparatus, they could have revealed the polymers in all their intricacy.
I heir molecules were incredibly large, the molecular weight running as high as millions of units, whereas simple organic substances such as, for instance, sugar and gasoline have molecular weights in the range of only about 50-500.
The giant molecules can be composed of a large number of repeating units, they being given the name «polymer» from the Greek words «poly»- many and «meros» — a part. Most polymers have the form of long flexible chains. Having found out that, chemists began synthesizing artificial polymers. This has led to the establishment of industries producing synthetic fibres and numerous polymeric materials, many of which were less expensive and superior in various ways to the natural materials.
As for plastics themselves, there are two kinds — those which are affected by heat and those which are not, or cast plastics and moulded plastics. Cast plastics are manufactured as liquid resins and are then cast in the desired forms. Moulded plastics are usually mixed with "fillers» to strengthen the finished material and give certain characteristics.
Now it is quite clear that the production of synthetic polymers is very important.
Scientists work hard at this problem. It is quite clear that science will continue to create new polymers and our industry and agriculture will receive cheap new materials with valuable properties.
I. Answer the following questions:
1. What does life fundamentally depend on?
2. How has a new industry of man-made organic polymers appeared?
3. What properties do synthetic polymers possess?
4. Could synthetic polymers compete with metals and ceramics?
5. What molecular weights have organic substances?
6. How did chemists begin synthesizing artificial polymers?
7. There are two kinds of plastics, aren’t there?
II. Speak on the nature of polymeric materials using the following word-combinations:
— organic polymers, list of natural organic products;
— modem methods of physical and chemical analyses;
— properties of synthetic polymers;
— the molecular weight of organic substances;
— the molecular weight of polymer;
— number of repeating units;
— synthesizing artificial polymers;
— cast plastics, moulded plastics.