The nature of polymeric materials

Read the text, translate it in written form using dictionary.

Read and translate the sentences. Correct the false statements.

EXERCISES

VOCABULARY

marketability -товарність brushability –придатність до роботи пензликом brush marks -мазки, сліди пензликiв adequately –відповідним чином, рівномірно similarly -аналогічно rheology -реологія conventional -звичайний

shear -відшаровуватися drilling muds -бурильне мастило (шлам) to lubricate -змащувати drill bit -бурильне свердло rock chips –уламки породи oil well -нафтова свердловина at rest -в стані покою foodstuffs -харчові продукти in respect to – відносно

1. If the paint is too thin it will adequately cover a surface. 2. The art of paper coating is dependent on the rheology of the coating material. 3. The petroleum industry uses small quantities of drilling muds. 4. Muds should exhibit viscosity under shearing. 5. Most foodstuffs are non-newtonian in behaviour.

Plastics have established themselves as active competitors to the older materials of construction, even on the score of price, and the rapid growth of the plastic industry is attributable in part to the utilization of this group of materials for industrial construction. Of the vinyl resins, polyvinyl chloride is perhaps most widely used and is fabricated in sheets and drawn in tubes by welding. Sharp-tipped tools and high machine speeds produce the best results with this class of material. However, where dimensional stability is of paramount importance the filled phenolics still lead the field. This material is used as the material of construction not as a lining, even to very large units of equipment. By selecting the filler this may be produced as a thermal and electrical insulator or conductor. The material is fabricated by moulding, so that roughly speaking, any detail that can be cast in iron can be formed from a filled phenolic, but where flatsided vessels are involved, plates are fabricated by joining with chemically accelerated cements, and this can be done in situ.

Life depends fundamentally on organic polymers. These polymers provide not only food but also clothing, shelter and transportation.

Indeed nearly all the material need 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, papers, paints and so on. The organic polymers from which such things could be made include proteins, cellulose, starch, resins, and a few other classes of compounds.

Modern methods of physical and chemical analyses have uncovered the principles that govern the properties of the natural polymers. On the basis of the discovery involved a new industry of man-made organic polymers has appeared. One could list the principal products: such as fibers, synthetic rubbers, coatings, plastics. Plastics and synthetic coating are already in common use.

Synthetic polymers now available already possess several of the properties required in a structural material. They are light in weight, easily transported, easily repaired, highly resistant to corrosion and solvents, and satisfactorily 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”. The natural polymers such as proteins, cellulose and other dominated his existence and even in ancient times people used these materials.

Yet as late as at the end of the 19th century polymer chemistry got little attention. Chemists attacked sugar, glycerol, fatty acids, alcohol and other organic compounds. But only feeble efforts were made to investigate such common materials as wood, starch, wool, silk. The substances composing these materials couldn’t be crystallized from solution, nor could they be isolated by distillation.

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. Their molecules were very large, the molecular weights running as high as million units, whereas simple organic substances such as sugar and gasoline have molecular weight in the range of only about 50-500.

The giant molecules can be composed of a large number of repeating units. Most polymers have the form long, flexible chains. Having found out that, chemists began synthesizing artificial polymers. This has led to the establishment of industries producing synthetic fibers and numerous polymeric materials.

Дата добавления: 2015-01-03