Nonmetallic materials

By the purpose they serve nonmetallic materials can be divided into a number of categories: constructional, lining, packing, sealing, paintwork, binding and others. They can be of the organic and inorganic origin.

Plastic materials form an independent group of nonmetals and play an important role in modern industry due to a number of valuable properties. Different plastics have different qualities, but they have some common qualities, first of all, they all are light and corrosion resistant.

Plastics, both organic and inorganic, are resinlike complex compounds based on natural or synthetic polymers and used for the manufacture of various products by molding methods. Polymers are high-molecular-mass resins whose basic molecules consist of the same group of atoms, called monomers. In addition to polymers plastics include fillers, stabilizers, hardeners, special additions and organic and inorganic matter.

The raw materials for the production of plastics are natural gas, oil by-products, coal and wood, which are readily available and quite cheap.

Plastic materials are classified by their application into: constructional plastics which are thermosetting compounds intended for machine elements; corrosion-resistant plastics, for example fluoroplastics and polyvinilchlorides, used to line acid tanks; heat-shielding materials which include asbestos-cloth laminates and glass-cloth-base laminates; packing-sealing plastics; electrical insulating materials, mainly paper-base laminates and fluoroplastics; antifriction materials, which are asbestos-cloth materials and others; translucent materials, for example, organic glass; and decorative materials, for example, paper- base laminates.

The products from plastic materials are mainly made by low-pressure molding, injection molding and sheet stamping. Molding is the most popular method of manufacturing parts from thermosetting plastics heated to 130-150° C. Plastics are easy to machine. The choice of cutting conditions depends on the specific properties of plastics.

Rubbers, or elastomers, are the products of processing special source materials with vulcanizing agents (sulfur) and various additives. The source materials for natural rubbers are gum resins obtained as the products of exudation of different trees and plants. Synthetic rubbers are polymeric materials similar in structure to plastic resins. Rubbers possess high elasticity and wear resistance, good electrical insulating properties, are chemically stable and air and water impermeable. That is why they find wide application in practically all industries, for example, in automotive-tractor industry.

Abrasive materials are nonmetals intended to finish structural materials. These are hard materials having rather sharp cutting faces. Natural abrasives include diamond, corundum and quartz. Manufactured abrasives are mostly artificial diamonds, silicon carbide and aluminum oxide, called synthetic corundum.

1. Find in the text English equivalents for the following words and word-combinations:

Неорганічного походження, призначені, умови різання, незалежний, різна продукція, ізолюючі матеріали, загальні властивості, досить дешеві, продукти обробки, гострі ріжучі грані, складні сполуки, хімічно стійкий, продукти обробки.

1. Answer the questions:

1. What is the origin of nonmetallic materials?

2. How are nonmetallic materials classified?

3. What materials are called plastics?

4. What do you know about the composition of plastics?

5. What are plastics made of?

6. What methods are usually used to make products from plastics?

7. What is the difference between natural and synthetic rubbers?

8. Why are rubbers widely used?

9. What purpose do abrasive materials serve?