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The homeland of Hevea is Brazil. Hevea grows best near the equator in the so-called rubber belt - a strip 2,600 kilometers wide.
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Depending on the tissues in which rubber accumulates, rubber-bearing plants are divided into: parenchymal (in roots and stems), chlorenchymal (in leaves and young shoots), latex (in milky sap).
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The juice from the tank is poured into special pools. Latex is a complex mixture of organic and mineral substances. To isolate rubber, it must be mixed with formic acid. Latex curdles like milk. The coagulation process lasts 12 hours.
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Cambodia is a small charming kingdom in Indochina, which was previously a large powerful empire of Southeast Asia during the period of the 9th-14th centuries - the Khmer Empire
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Natural rubber Gutta-percha Synthetic rubber Cis-polyisoprene (2-methylbutadiene-1,3) (-CH3-CH=c(CH3)-CH2-)n Trans-polyisoprene (spatial isomer) 1) Butadiene (divinyl) (-CH2-CH =sn-sn2-)n 2) Butadiene-styrene (-sn2-sn=sn-sn2-sn2-sn(s6n5)-)n 3) Butadiene-nitrile (-sn2-sn=sn-sn2-sn2-sn( сN)-)n 4)Isoprene (-СН2-с(СН3)=СН-СН2-)n 5) Chloroprene (-СН2-СН(cl)=СН-СН2-)
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History of the discovery of rubber. Man met rubber for a long time. In tropical countries, there are still trees that produce rubber. In Mexico, for example, there are excavations in which rubber balls were found. These balls served for ritual purposes. Columbus's companions found the inhabitants of the island of Haiti playing ball. It is interesting to note that they still have this game to this day. The Europeans, of course, were also amazed by the unusual properties of the balls. The information obtained was recorded in the works of Spanish historians of the early 17th century, and from them we learned that the substance from which balls are made is obtained from the sap of a special tree. Samples of rubber were brought to Europe and kept in museums as rarities. 100 years later, in the first quarter of the 18th century, the French Academy of Sciences sent an expedition to South America to measure the length of the meridian. The expedition included the energetic scientist La Condamine. Having become interested in rubber, he found out about its extraction and use in Brazil. His notes are very instructive in this regard. They came out in 1735, and from them we learn the following: the tree from which rubber was extracted is called Hevea. When it is cut, white milky juice flows out, drying in the air and darkening at the same time. They impregnated fabrics with it to make them waterproof, made torches from dried resin, and also obtained special bottles in the form of syringes - hollow elastic vessels from which water can be thrown to great heights.
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PRACTICAL PART. We will try to obtain natural rubber in laboratory conditions, using the milky sap of ficus. We are collecting latex. To do this, we cut off several young leaves, collect the released juice and weigh it, since the quantities of substances given below are indicated for every 30 grams of latex. 2) Add to the collected latex 50 milliliters of a 40% solution of ammonium chloride NH4CI or 50 milliliters of a 25% solution of calcium chloride CaCI2. To destroy the shell surrounding the rubber particles. 3) After 30 minutes, add 50 milliliters of 96% C2H5OH to the resulting solution. After this, the rubber particles will stick together into droplets. 4) After 5-6 minutes, filter the solution through gauze. 5) Collect the filtered rubber with a glass rod preheated to a temperature of 55-60 degrees Celsius. Rubber cannot be made from such rubber, but you can test the properties of rubber. The total yield of rubber (from 30 grams of latex) ranges from 6.5 to 9 grams. In a similar way, rubber can be obtained from the milky juice of dandelion.
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Target:
Familiarization of students with the properties of natural rubber, its composition and structure, vulcanization
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Plan:
1. History of the discovery of rubber. 2. Natural rubbers: composition, structure, properties 3. Synthetic rubbers: receipt, classification, application 4. Vulcanization.
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Introduction
Rubber is a high-molecular compound, a polymer. There are two types of rubber: natural and synthetic. The monomer (elementary unit) of natural rubber has the following composition and structure: CH2═ C─CH═CH2 │ CH3 Name: 2-methylbutadiene 1,3.
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1. History of the discovery of rubber.
Currently, the history of the discovery of rubber dates back to the time when Columbus brought an elastic ball from the New World to Spain, which had the property of bouncyness. The Indians made such balls from the sap of the Hevea plant; they called this juice “caucha,” which meant “tears of the milky tree.”
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Natural rubber
Natural rubber (NR) is a high-molecular unsaturated hydrocarbon, the molecules of which contain a large number of double bonds; its composition can be expressed by the formula (C5H8)n (where the value of n ranges from 1000 to 3000).
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Natural rubber contains 91-96% polyisoprene hydrocarbon (C5H8)n, as well as proteins and amino acids, fatty acids, carotene, small amounts of copper salts, manganese, iron and other impurities. Natural rubber polyisoprene is a stereoregular polymer. Almost all 98-100% isoprene units in the macromolecule are attached in the cis-1,4 position:
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Natural rubber – cis-polyisoprene
Structure: structurally regular (1,4-polymerization); stereoregular (all links are cis - structure). Macromolecules can curl into balls and, when stretched, straighten out. Properties: resilient, elastic, wear-resistant in a small temperature range
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Gutta-percha, natural isomer – trans-polyisoprene
Structure: structurally regular (1,4-polymerization); stereoregular (all links of the trans structure) Macromolecules do not curl into balls, they are located close to each other. Properties: less elastic, high electrical insulation (underwater cable); a waste product of gutta-percha plants (euonymus).
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The first artificial - sodium butadiene rubber (synthesized by Lebedev S.V.)
Structure: no structural regularity (1,4- and 1,2-connections of units); there is no stereo regularity (there are links of cis structure and trans structure). Properties: less elastic and less wear-resistant.
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Nairit, neoprene - artificial polychloroprene rubber
Structure: structurally regular; stereoregular. Properties: non-flammable; wear-resistant; heat and light resistant; resistant to chemicals reagents; ability to stick together.
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Synthetic rubber
On instructions from the party, chemist Sergei Lebedev figured out how to synthesize rubber from ethyl alcohol, from which 1,3-butadiene was obtained. But he did not live to see the mass production of artificial rubber - he died of typhus.
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Types of synthetic rubbers:
Isoprene Butadiene Butadiene-methylstyrene Butyl rubber Ethylene-propylene Butadiene-nitrile Chloroprene Silicone Fluorine rubber Thiokols
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Isoprene
Isoprene is superior in wear resistance to natural rubber. Isoprene is used mainly in the manufacture of shoes, gloves and some knife handles.
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BUTADIENE
The main properties of butadiene are: high strength, tear resistance, elasticity and wear resistance. Butadiene is used in the production of linoleum, abrasive tools, conveyor belts, household products, etc.
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METHYLSTYRENE RUBBER
Used for most rubber products (including chewing gum).
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BUTYL RUBBER
Resistant to many aggressive environments. The most important application of butyl rubber is the production of tires. In addition, they are used in the production of various rubber products that are resistant to high temperatures.
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ETHYLENE-PROPYLENE RUBBER
Ethylene-propylene rubber is suitable for the production of hoses, insulation, anti-slip profiles, bellows. One of the many areas of application is coverings for outdoor sports and children's playgrounds.
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NITRILE BUTADIENE RUBBER
Advantages: very good resistance to oils (due to the content of nitrile compounds) and gasoline, excellent resistance to petroleum hydraulic fluids, good resistance to carbonaceous solvents, very good resistance to alkalis and solvents; wide range of operating temperatures (depending on composition): from -57°C to +120°C. Limitations: Low resistance to ozone, sunlight and natural oxidizing agents, poor resistance to oxidized solvents. [-CH2-CH=CH-CH2-]n - [-CH2-CH(CN)-]m
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CHLOROPRENE RUBBER
Good resistance to open fire; excellent ability to adhere to fabrics and metals; very good weather resistance, ozone resistance and resistance to natural oxidation; good resistance to abrasion and low temperature. Chloroprene rubber crystallizes when stretched, making rubber based on it have high strength. Production of rubber technical products: conveyor belts, belts, sleeves, hoses, diving suits, electrical insulating materials. They also produce wire and cable sheaths and protective coatings. Adhesives and chloroprene latexes are of industrial importance.
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SILOXANE RUBBER
Siloxane rubbers have the following properties: increased heat, frost and fire resistance, resistance to the accumulation of residual compression deformation, etc. They are used in very important areas of technology, and their relatively high cost is paid off by a longer service life.
Introduction Rubbers are natural or synthetic materials characterized by elasticity, water resistance and electrical insulating properties, from which rubber is obtained through special processing. Natural rubber is obtained from a milky-white liquid called latex - the milky sap of rubber plants. In technology, rubber is used to make tires for vehicles, airplanes, and bicycles; Rubbers are used for electrical insulation, as well as for the production of industrial goods and medical devices.
One Brazilian Hevea tree, on average, until recently, was capable of producing only 2-3 kg of rubber per year; The annual productivity of one hectare of hevea before the Second World War was kg of technical rubber. Such volumes of natural rubber did not satisfy the growing needs of industry. Therefore, there was a need to obtain synthetic rubber. Replacing natural rubber with synthetic rubber results in huge labor savings. Modern, ever-developing and increasingly complex technology requires good and different rubbers; rubbers that would not dissolve in oils and gasoline, withstand high and low temperatures, and would be resistant to oxidizing agents and various aggressive environments.
Production method using Lebedev's method In 1910, S.V. Lebedev was the first to obtain synthetic rubber and butadiene. The raw material for producing synthetic rubber was ethyl alcohol, from which 1,3-butadiene was obtained (it turned out to be a more accessible product than isoprene). Synthetic butadiene rubber was then obtained through a polymerization reaction in the presence of sodium metal. In 1926, the Supreme Economic Council of the USSR announced a competition to develop an industrial method for synthesizing rubber from domestic raw materials. By January 1, 1928, the jury had to submit a description of the method, a scheme for the industrial production of the product and 2 kg of rubber. The winner of the competition was a group of researchers headed by S. V. Lebedev, professor at the Medical-Surgical Academy in Leningrad. In 1932, it was on the basis of 1,3-butadiene that a large synthetic rubber industry arose. Two factories for the production of synthetic rubber were built. S.V. Lebedev’s method turned out to be more developed and economical. In the years S.V. Lebedev first synthesized a rubber-like substance during the thermal polymerization of divinyl and studied its properties. In 1914, the scientist began studying the polymerization of about two dozen hydrocarbons with a system of double or triple bonds. In 1925, S.V. Lebedev put forward the practical task of creating an industrial method for the synthesis of rubber. In 1927, this problem was solved. Under the leadership of Lebedev, the first kilograms of synthetic rubber were obtained in the laboratory. In 1930, using Lebedev’s method, the first batch of new rubber was produced at a pilot plant in Leningrad, and two years later the world’s first synthetic rubber production plant was put into operation in Yaroslavl.
Obtaining synthetic rubber In developing the synthesis of rubber, Lebedev followed the path of imitation of nature. Since natural rubber is a polymer of diene hydrocarbon, Lebedev also used diene hydrocarbon, only a simpler and more accessible one - butadiene. The raw material for producing butadiene is ethyl alcohol. The production of butadiene is based on the reactions of dehydrogenation and dehydration of alcohol. These reactions occur simultaneously by passing alcohol vapor over a mixture of appropriate catalysts: Butadiene is purified from unreacted ethyl alcohol and numerous byproducts and subjected to polymerization. In order to force the monomer molecule to connect with each other, they must first be excited, that is, brought to a state where they become capable of mutual attachment as a result of the opening of double bonds. This requires the expenditure of a certain amount of energy or the participation of a catalyst. During catalytic polymerization, the catalyst is not part of the resulting polymer and is not consumed, but is released at the end of the reaction in its original form. As a catalyst for the polymerization of 1,3-butadiene, S. V. Lebedev chose metallic sodium, first used for the polymerization of unsaturated hydrocarbons by the Russian chemist A. A. Krakau. A distinctive feature of the polymerization process is that the molecules of the original substance or substances combine with each other to form a polymer, without releasing any other substances.
Slide 1
Organic chemistry grade 10. School collection
Moscow, 2004
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1. A little history 2. Chemical structure of natural and synthetic rubber and rubber 3. Rubber 4. The concept of terpenes 5. Obtaining rubber 6. Application of rubber
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1. A little history
The homeland of rubber is Central and South America.
Brazilian Hevea (Hevea brasiliensis)
30% natural polymer
Milky white
Emulsion
"Tears of a Tree" - sao-o-Chu
Cao – tree, o-Chu – cry
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A little history of the 15th century
Impregnation of boats, baskets, clothes with milky juice - do not allow water to pass through.
Torches - burn for a long time, pleasant smell
Unbreakable container for liquids
Rubber shoes
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A little history of the 18th – 19th centuries
In the first half, samples reached Europe
Balls that bounce when hit
The first pencil erasers
1823 Charles Mackintosh invented waterproof fabric. The raincoats were called "Mackintosh". The production of galoshes has been established.
1832 The first shoe factory with rubber coating was built in St. Petersburg.
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A little history 1832 - the German chemist Ludesdorff found that
K a u ch u k FROST HEAT fragile soft
resilient and elastic
SULFUR + TURPENESS
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A little history of the 19th century.
1839 Vulcanization of rubber was discovered by C. Goodyear, a merchant of various goods
1843 Englishman T. Hancock discovered a similar method and called it vulcanization, and the new product rubber
The need for rubber increased sharply, and in 1876, Hevea seeds were secretly exported from Brazil and distributed in the countries of Southeast Asia and Africa.
1888 The rapid development of the automobile industry posed the task of producing synthetic rubber.
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2.Structure of natural and synthetic rubber.
POLYMERS ELASTOMERS PLASTICS FIBERS rubber rubber ebonite
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Chemical structure of natural rubber.
CH2 CH2 - CH2 CH2 - . . .
Natural rubber is cis-polyisoprene.
Rubber in which all the elementary units are in either a cis or trans configuration is called stereoregular.
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Chemical structure of synthetic rubber.
The composition of natural rubber was known already in the second half of the 19th century.
Bouchard's 1875 Isolation of Isoprene from Natural Rubber
B U T A D I E N O V Y K A U C H U K
USSR according to the method of S.V. Lebedeva 1931
The tire was manufactured and ran for 16,000 km.
1957 B.A. Dolgoplosk I.A. And Korotkov obtained butadiene rubber with a stereoregular structure.
Divinyl rubber
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When rubber with sulfur is heated, individual polymer chains are cross-linked due to the formation of disulfide bridges.
Rubber structure diagram
…CH2-CH-CH-CH2-… (S)n …-CH2-CH-CH-CH2-… RUBBER
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4. Understanding terpenes
These are hydrocarbons whose structural fragment is isoprene. They have a common “generic” name -TERPENS and have the general formula (C5H8)n
They are a component of essential oils.
OCIMENE is contained in the basilica.
LIMONENE is found in citrus peels.
SQUALENE isolated from shark liver
ß – CAROTENE is found in carrots
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The concept of terpenes
CH2=C-CH2-CH2-CH=C-CH=CH2
CH3 ocimene CH3 CH2 C limonene
Essential oils are oily products that are insoluble in water and completely evaporate. Used for preparing fragrant compositions. First used 2100 BC. e. under King Hamurappi.
IntroductionRubbers - natural or
synthetic materials,
characterized by elasticity,
waterproof and
electrical insulating properties,
of which by special
processing produces rubber.
Natural rubber is obtained from
milky white liquids
called latex - milky
juice of rubber plants.
In technology, rubber is used to make
tires for vehicles,
airplanes, bicycles; rubbers
used for electrical insulation, and
also industrial production
goods and medical devices.
Since 1932, according to Lebedev’s method, the world’s first synthetic rubber industry began to be created in the USSR
Method of production using Lebedev's method
In 1910, S.V. Lebedev was the first to obtain synthetic rubber andbutadiene. The raw material for producing synthetic rubber was ethyl alcohol, from
which 1,3-butadiene was obtained (it turned out to be a more accessible product than
isoprene). Then, through a polymerization reaction in the presence of a metal
sodium produced synthetic butadiene rubber.
In 1926, the Supreme Economic Council of the USSR announced a competition to develop an industrial method
synthesis of rubber from domestic raw materials. By January 1, 1928, the jury needed
provide a description of the method, a scheme for the industrial production of the product and 2 kg
rubber The winner of the competition was a group of researchers led by
Professor of the Medical-Surgical Academy in Leningrad S. V. Lebedev.
In 1932, it was on the basis of 1,3-butadiene that a large industry arose
synthetic rubber. Two factories were built for the production of synthetic
rubber S.V. Lebedev’s method turned out to be more developed and economical.
In 1908-1909, S.V. Lebedev was the first to synthesize a rubber-like substance
during the thermal polymerization of divinyl and studied its properties. In 1914, the scientist
began studying the polymerization of about two dozen hydrocarbons with
system of double or triple bonds.
In 1925, S.V. Lebedev put forward the practical task of creating an industrial
rubber synthesis method. In 1927 this problem was solved.
Under the leadership of Lebedev, the first kilograms were obtained in the laboratory
synthetic rubber.
In 1930, using Lebedev’s method, the first batch of new rubber was obtained at
pilot plant in Leningrad, and two years later the first one was put into operation in Yaroslavl
the world's largest synthetic rubber plant.
Obtaining synthetic rubber
In the development of rubber synthesis, Lebedev followed the path of imitationnature.
Since natural rubber is a polymer of diene hydrocarbon, then
Lebedev also used diene hydrocarbon, only more
simple and affordable - butadiene
The raw material for producing butadiene is ethyl alcohol. Receipt
butadiene is based on the reactions of dehydrogenation and dehydration of alcohol.
These reactions occur simultaneously when alcohol vapor is passed over
a mixture of appropriate catalysts:
Butadiene is purified from unreacted ethyl alcohol,
numerous by-products and undergo polymerization.
In order to force the monomer molecules to connect with each other,
they must first be aroused, that is, brought into such
state when they become capable, as a result of disclosure
double bonds to mutual addition. This requires costs
a certain amount of energy or catalyst participation.
In catalytic polymerization, the catalyst is not included in the composition
of the resulting polymer and is not consumed, but is released at the end
reactions in their original form. As a catalyst
polymerization of 1,3-butadiene S. V. Lebedev chose metal
sodium, first used for the polymerization of unsaturated
hydrocarbons by the Russian chemist A. A. Krakau.
A distinctive feature of the polymerization process is that
in this case, the molecules of the original substance or substances are connected between
themselves to form a polymer, without releasing any other
substances.
