Ebonite sheet is a highly vulcanized product of natural or synthetic sulfur rubber. The bound sulfur in ebonite is about 32%, which corresponds to the formula (C6H9S)2. Ebonite is usually dark brown or black in color.
Ebonite lends itself well to machining; non-hygroscopic, does not adsorb gases, resistant to acids and alkalis, swells in carbon disulfide and petroleum products, dissolves in paraffin at temperatures above 300°C with the release of hydrogen sulfide. Under the action of sunlight due to oxidation, the insulating properties of ebonite decrease. Ebonite softens usually between 70°C and 80°C and hardens again when cooled; at temperatures ≥200°С it chars without melting.
The rubber used for the manufacture of ebonite must be completely free from contaminants that lead to the formation of bubbles, which reduce electrical insulating properties and make machining difficult. The most valuable grades of ebonite contain only rubber (~66 parts by weight) and sulfur (~34 parts by weight).
Ebonite dust, talc, pumice, white soot, diatomaceous earth and others are used as fillers for ebonite. Soot is introduced in small amounts of 3-5%) to color ebonite black (high doses of soot worsen the dielectric properties).
Ebonite is produced in the form of plates, rods and tubes and is used for the manufacture of electrical products, especially those that must be resistant to acids (accumulator tanks), as well as containers for storing acids and alkalis.
Ebonite is a hard hard variety of rubber, devoid of characteristic elasticity, having a dark brown or black color, less often a sandy tint. It has high electrical insulating qualities, due to which it is used in the manufacture of complex precision electrical appliances, and the separation of conductors.
How and from what is ebonite made?
The production of ebonite is carried out in a similar way as the production of rubber, the difference lies in the ratio of components, as well as the absence of some additives. This material is a natural or synthetic rubber that has undergone a vulcanization process after mixing with sulfur.
Due to heating and proximity to sulfur, the rubber becomes solid. Other components, in particular dyes, can be additionally included in its composition. For example, to obtain black ebonite, 5% soot is added. The material is harder than rubber, as it contains about 30% sulfur by weight of rubber. The latter has only 1-5%, sometimes more. There are grades of ebonite in which the proportions of sulfur and rubber are the same.
The value and qualities of ebonite depend on the degree of its purity. The best is considered to be a material that consists only of sulfur and rubber. Moreover, the concentration of the first is 35%. The inclusion of soot for tinting is accompanied by a decrease in the cost of the material, and most importantly, its dielectric qualities.
ebonite properties
Ebonite is characterized by qualities that other rubber products do not have. In general, its key characteristics include:
Possibility of machining.
Moisture resistance.
Gas-tight.
Acid resistance.
dielectric properties.
Fire resistance.
Due to the hardness, the processing of ebonite is not much different from working with plastics. It can be cut, sawed, sharpened, ground, polished, drilled. What are the decorations carved from ebonite worth. This material is not only convenient, but also pleasant to work with. After polishing, it acquires a rather attractive appearance. But this applies only to types of ebonite with certain dyes. Technical material with a brown tint is processed well, but it will not work to get an outwardly attractive product from it.
Ebonite is characterized not only by moisture resistance, but by the complete absence of hygroscopicity. When immersed in water, ebonite does not absorb it at all. This quality is no longer so important, but before the advent of a wide variety of plastics, it had no analogues. The material is used for the manufacture of cups, toys, door handles, knife handles. Also, gases do not pass through it. This allows the material to be used for the manufacture of battery cases. It perfectly protects the environment from electrolyte evaporation.
The material also tolerates contact with many types of acids that can corrode the metal. Its chemical resistance is also manifested by its resistance to damage by fats and salts. Ebonite is a prime example of a dielectric. It absolutely does not pass electric current, even when applying large charges. Rubber has the same property. But large electrical discharges can pierce through it. The ebonite surface is impenetrable for them. It's all about the higher particle density.
The hardness of the material can be compared with ivory. For this reason, products made from it have a high resistance to abrasion. But it should be noted that when the temperature drops, it becomes brittle. Breaking it in the cold will not be difficult.
Ebonite is generally characterized by inertness. He does notacts on other substances in contact with it. This eliminates the change in the density of chemically active substances. Tubes from it are used to connect vessels with chemical reagents. By this quality, it can be equated to glass, but only under conditions of work with certain liquids, to which it has full resistance.
The surface of ebonite cannot be set on fire. When exposed to open fire, it simply chars. This distinguishes it from rubber. In the latter, due to a smaller amount of sulfur, stable combustion occurs with the release of a large amount of soot. Moreover, if the ebonite surface is heated to +300°C, it will melt. If the temperature is equal to + 70 ° C, then it will become pliable, it can be bent, giving the necessary shape. It is for this reason that the material has given way to plastics at the household level. Now they no longer make those products that were made before. He became a purely insulator for electrical conductors, where he has no equal.
The recommended temperature range for using ebonite is from -50 to +60°C. Within such limits, the material has sufficient strength and rigidity. With greater cooling, it becomes critically brittle. Overheating ends with flexibility. It is impossible to work with ebonite as with plastic, in terms of melting and casting. When heated, it simply begins to char as a result of contact with oxygen. But you can still melt ebonite. To do this, it is placed in a paraffin bath. Moreover, such an action is more like dissolution, since it will not work to separate it. This does not give real results, since secondary processing by melting for ebonite is not available.
Heated, it can be softened and then pressed into the desired shape. It is impossible to achieve fluidity with the possibility of flowing into small cavities. The maximum that can be done is to compress another similar form from an ebonite product of one form. For example, to get a cylinder from a parallelepiped.
It should be noted that the material does not tolerate direct sunlight. It oxidizes. As a result, a greenish coating appears on it. In this regard, they try to use it on products that do not come into contact with ultraviolet radiation. Also, the disadvantages of ebonite include intolerance to certain hydrocarbons. That is, oil products are contraindicated for him. In particular, this applies to gasoline and oil, which corrode it.
Use of ebonite
For most people, ebonite is associated with the lessons of physics, in connection with a memorable experiment in electrifying bodies. If you rub an ebonite stick on silk, wool or hair, then it will begin to attract small pieces of paper for some time. This is a visual guide to electrification. But in fact, the material is much more in demand in the industry than just the manufacture of scientific equipment for the school curriculum.
The main value of ebonite is in its dielectric qualities and pronounced chemical resistance. For this reason, it is used in the manufacture of batteries. The internal partitions between the fields of the batteries are made from it. They also share other electrical capacities. The electrolytes inside the batteries are absolutely safe for him.
Still, the production of batteries, even with the advent of plastics, is not the only area where ebonite is used. It is used in the following areas:
Electrical engineering.
Hand made souvenirs.
Medicine.
Radioelectronics.
Medical equipment, etc.
Initially, at the time of invention in the 18th century, the material was used to make various crafts. Chess was cut out of him, knife handles, buttons, bracelets, etc. were made. It was very popular at the time as there were no plastics. With the development of the direction of electricity in the 20th century, it was possible to use it as a dielectric. It can be found in the design of transformers, batteries, electrical measuring instruments.
Currently, ebonites are practically replaced by plastics, which are superior to ebonites in terms of dielectric properties, chemical and temperature resistance. However, an ebonite stick is in the physics classroom at every school, as it is the simplest source of obtaining a negative charge when rubbing wool against it.
In production
Ebonites were used as electrical insulators and acid-resistant materials in the production of electrical insulating parts of devices, in the rubberizing of various containers for aggressive liquids, cases of acid batteries, etc.
Ebony was also used as a substitute for expensive materials like ebony, ivory, horn, or tortoiseshell.
In industry
At the beginning and middle of the 20th century, combs, knife handles, mouthpieces for cigarettes and smoking pipes, cases of fountain pens, in music - gramophone records, mouthpieces for clarinets, saxophones and bassoons were made from ebonites. Pipes, flutes and clarinets are also made.
Advantages and disadvantages
We offer you to understand what positive aspects are hidden in this product:
Hygroscopicity. This property allows the use of products based onebonite in the open air, without fear for the weakening of the properties from moisture. Dielectric properties, which are in demand more than others, will not weaken under any circumstances.
Ease of processing. This positive property allows you to give ebonite parts a variety of shapes. Not so long ago, decoration elements were cut out of them, handles for knives and handles for cutlery were made. The modern possibility of milling and laser processing allows you to apply graphics and text on the surface of the processing.
The material is easy to grind. Both mechanical and manual processing is acceptable. At the same time, the latter takes more time, but in small volumes of production it takes place, as well as at the stages of fitting the mold.
Does not affect other, surrounding materials. This property allows not to change the density of chemically active media, as well as taste. For example, the bases of smoking pipes are made from ebonite. At the same time, even with direct contact with the human mucosa, the material does not in any way harm health and does not spoil the taste.
Large scope. You have seen for yourself how many variations are possible based on this product. Moreover, this applies not only to forms, but also to color, features of operation, type of blanks and other features.
At the same time, the scope is also based on affordability in terms of price. The latter applies only to blanks, since what has already been processed by the manufacturer, including jewelry, a mouthpiece, decorative elements and other things, are not cheap.
Does not burn. It is impossible to set fire to the workpiece, which at least guarantees that the ebonite dielectric will not cause a fire in electrical equipment. But, it is heating that is an important processing step, since it allows you to give products various shapes, up to bending into a circle.
It is important that the processing temperature can be raised in steps, starting from 70 degrees for a small deformation and ending with 300 degrees Celsius for complete melting into a viscous substance.
There are almost no shortcomings. Unless, during processing, specialists highlight the fragility of the material. Namely, you should not drop ebonite products, subject them to excessive friction and shock. The brittleness properties are enhanced at negative temperatures, which is important in electrical installations. Therefore, in the latter case, ebonite is always used in the case to protect it from accidental falling.
It is due to the fact that already at a temperature of more than 60 degrees Celsius, ebonite softens, it is abandoned, replacing it with plastic. However, the operating temperature range is not always positive. On the contrary, the manufacturer claims the possibility of applying from -50 to +50 degrees. Recall that the product is completely melted only at a temperature of +300 degrees in paraffin.
If dielectric properties are important, be sure to protect the dielectric with a case, otherwise it will lose its properties. Where this is not important, for example, in jewelry and decorative products, the manufacturer either initially gives the raw material a greenish tint to avoid fading, or adds carbon black to the composition, which increases the black pigment. Greenish ebonite in the photo, as in life, looks attractive.
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