Natural rubber , also called Indian rubber or caoutchouc , as originally produced , comprising a polymer of isoprene organic compounds, with small impurities from other organic compounds, plus water. Malaysia and Indonesia are the two leading rubber producers. The forms of polyisoprene used as natural rubber are classified as elastomers.
Currently, rubber is harvested mainly in the sap form of rubber trees or else. Latex is a sticky and soft colloid that is pulled by making an incision in the bark and collecting fluid in a blood vessel in a process called "wiretapping". Latex is then refined into a rubber ready for commercial processing. In the main area, latex is allowed to clot in collection cups. Lumpy bumps are collected and processed into dry forms for marketing.
Natural rubber is widely used in many applications and products, either alone or in combination with other materials. In most of its useful forms, it has a large stretch ratio and high resistance, and is highly water resistant.
Video Natural rubber
Variety
Hevea brasiliensis
The main commercial sources of natural rubber latex are Pará ( Hevea brasiliensis rubber trees, spurge family members, Euphorbiaceae . This species is preferred because it grows well under cultivation. Well-managed trees respond to wounds by generating more latex over several years.
Congo rubber
Congo Rubber, formerly a major source of rubber, originated from vines in the genus Landolphia L. kirkii , L. heudelotis , and L. Owariensis ).
Dandelion
Dandelion milk contains latex. Latex shows the same quality as natural rubber from a rubber tree. In the wild type of dandelion, the latex content is very low and varies. In Nazi Germany, the research project tried to use dandelion as a rubber production base, but failed. In 2013, by inhibiting one key enzyme and using modern cultivation methods and optimization techniques, scientists at the Fraunhofer Institute for Molecular Biology and Applied Ecology (IME) in Germany developed a cultivar suitable for commercial production of natural rubber. Working in conjunction with Continental Tire, IME started the pilot facility.
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Many other plants produce latex forms that are rich in isoprene polymers, although not all produce polymers that can be used as easily as Pará. Some of them require a more complicated process to produce something like usable rubber, and most are more difficult to tap. Some produce other desirable materials, eg gutta-percha ( Palaquium gutta ) and chicle of the Manilkara species. Others that have been commercially exploited, or at least show promise as a source of rubber, including rubber figures ( Ficus elastica ), Panama rubber trees ( Castilla elastica ), various spores > Euphorbia spp.), Lettuce ( Lactuca species), related Scorzonera tau-saghyz , various species Taraxacum , including dandelion ( Taraxacum officinale ) and Russian dandelion ( Taraxacum kok-saghyz ), and perhaps most important for the hypoallergenic, guayule (Parthenium argentatum ). The term rubber rubber is sometimes applied to natural rubber obtained from trees to distinguish it from synthetic versions.
Maps Natural rubber
History
The first use of rubber is by native Mesoamerican culture. The earliest archaeological evidence of the use of natural latex from the tree Hevea comes from the Olmec culture, where rubber was first used to make the ball for the Mesoamerican ballgame. Rubber is then used by Maya and Aztec cultures - besides making Aztec balls use rubber for other purposes such as making containers and making water-resistant textiles by planting them with latex rubber.
Paras rubber tree is customary to South America. Charles Marie de La Condamine is credited with introducing rubber samples to the French acadà © Ã… © Royale Royale des Sciences in 1736. In 1751, he presented a paper by FranÃÆ'§ois Fresneau to the AcadÃÆ' © nie (published on 1755) which describes many properties of rubber. This has been referred to as the first scientific paper on rubber. In England, Joseph Priestley, in 1770, observed that a piece of material is great for rubbing pencil on paper, that is the name "rubber". Slowly walking around England. In 1764 FranÃÆ'§ois Fresnau found that turpentine was a rubber solvent. Giovanni Fabbroni is credited with the discovery of naphtha as a rubber solvent in 1779.
South America remained a major source of latex latex rubber used during the 19th century. The trade is highly protected and exporting Brazilian seeds is a violation of the law, although no law prohibits it. However, in 1876, Henry Wickham smuggled 70,000 rubber seeds from Brazil and sent them to Kew Gardens, England. Only 2,400 germinated. Seeds were then shipped to India, Ceylon England (Sri Lanka), Indies (Indonesia), Singapore, and British Malaya. Malaya (now Peninsular Malaysia) later became the largest rubber producer. In the early 1900s, Congo-Free State in Africa was also a significant source of natural rubber latex, mostly collected by forced labor. King Leopold II's colonial state imposed brutal production quotas. Tactics to enforce rubber quotas include removing the victim's hand to prove that they have been killed. Soldiers often returned from raids with baskets full of broken hands. Opposed villages were demolished to encourage better adherence locally. See Cruelty in Congo-Free Countries for more information on rubber trade in Congo-free Countries in the late 1800s and early 1900s. Liberia and Nigeria start production.
In India, commercial cultivation was introduced by British planters, although experimental efforts to grow rubber on a commercial scale began in 1873 in the Calcutta Botanical Gardens. The first commercial plantation Hevea was established at Thattekadu in Kerala in 1902. In recent years the estates were expanded to Karnataka, Tamil Nadu and the Andaman and Nicobar Islands of India. India is currently the third largest producer in the world and the 4th largest consumer.
In Singapore and Malaya, commercial production was heavily promoted by Sir Henry Nicholas Ridley, who served as the first Scientific Director of the Singapore Botanic Gardens from 1888 to 1911. He distributed rubber seeds to many planters and developed the first technique to tap trees for latex. without causing serious damage to the tree. Due to the strong promotion of this plant, he is popularly remembered by the nickname "Mad Ridley".
Pre-World War II
Charles Goodyear developed vulcanization in 1839, though Mesoamericans used a steady rubber for ball and other objects in the early 1600 BC.
Prior to World War II significant uses included profiles of doors and windows, hoses, belts, gaskets, webbing, floors and dampers (antivibration mounts) for the automotive industry. The use of rubber in automobile tires (initially solid and not pneumatic) typically consumes large amounts of rubber. Gloves (medical, household and industrial) and toy balloons are large consumers of rubber, although the type of rubber used is concentrated sap. Significant rubber tonnage is used as an adhesive in many manufacturing industries and products, although the two most notably are paper and carpet industries. Rubber is commonly used to make rubber bands and pencil erasers.
Rubber produced as a fiber, sometimes called 'elastic', has significant value for the textile industry because of its excellent elongation and recovery properties. For this purpose, made rubber fibers are made as extruded spherical fibers or rectangular fibers cut into strips of extruded films. Due to the low acceptance, taste and appearance of the dye, the rubber fibers are covered by yarns of other fibers or directly woven with other threads into the fabric. Rubber threads are used in foundation clothing.
While rubber is still used in textile manufacturing, its low strength limits its use in light clothing because latex has no resistance to oxidizing and is damaged by aging, sunlight, oil and sweat. The textile industry turns to neoprene (polymer chloroprene), a kind of synthetic rubber, and other more commonly used elastomer fibers, spandex (also known as elastane), because of its superiority to rubber both in strength and endurance.
Properties
Rubber shows unique physical and chemical properties. Rubber stress-strain behavior exhibits the effects of Mullins and Payne's effects and is often modeled as hyperelastic. Rubber strain crystallizes.
Due to the presence of double bonds in each repeating unit, natural rubber is vulnerable to vulcanization and sensitive to ozone cracking.
The two main solvents for rubber are turpentine and naphtha (petroleum). Because the rubber is not easily soluble, the material is subtly divided by chopping before dipping.
Ammonia solution can be used to prevent coagulation of raw latex.
The rubber begins to melt at about 180 ° C (356 ° F).
Elasticity
On a microscopic scale, relaxed rubber is a collection of irregular and fickle chain of wrinkles. In a rubber stretched, the chain is almost linear. The restoring force is caused by more conformation of wrinkles than the more linear ones. For quantitative treatment, see the ideal chain, for more examples see entropic style.
Cooling below the glass transition temperature allows local conformational changes but reordering is practically impossible due to a larger energy barrier for longer chain joint movements. Low 'frozen' rubber elasticity and strain results from small changes in length and bond angle: this causes the Challenger disaster, when the American Space Shuttle's flat o-ring fails to relax to fill the widening gap. Glass transitions are fast and reversible: force back on heating.
The rubber parallel chain stretches vulnerable to crystallization. This takes time because the twisted turns of the chain must move out of the way of growing crystal. Crystallization has occurred, for example, when, after days, inflated toy balloons found to wither at relatively large volumes of left. When touched, it shrinks as the temperature of the hand is sufficient to melt the crystals.
Rubber vulcanization creates disulfide bonds between chains, limiting degrees of freedom and producing tightening chains faster for certain strains, thereby increasing the constant elastic strength and making the rubber harder and less extensible.
Malodour
Crude rubber storage and rubber processing depots can produce a serious malodour to be a source of complaints and protests for those living in the vicinity.
Microbial dung originates during the processing of rubber blocks. The impurities are damaged during storage or thermal degradation and produce volatile organic compounds. Examination of these compounds using gas chromatography/mass spectrometry (GC/MS) and gas chromatography (GC) shows that they contain sulfur, ammonia, alkene, ketones, esters, hydrogen sulfites, nitrogen and low molecular weight fatty acids (C2-C5 ). ).
When the latex concentrate is produced from rubber, sulfuric acid is used for coagulation. It produces malodourous hydrogen sulfide.
Industry can reduce this bad odor with scrubber system.
Chemical makeup
Latex is a cis-1,4-polyisoprene polymer - with a molecular weight of 100,000 to 1,000,000 daltons. Typically, a small percentage (up to 5% of dry mass) of other ingredients, such as proteins, fatty acids, resins, and inorganic materials (salts) found in natural rubber. Polyisoprene can also be made synthetically, producing what is sometimes referred to as "synthetic natural rubber", but synthetic and natural routes are different. Some natural rubber sources, such as gutta-percha, are composed of trans-1,4-polyisoprene, structurally similar structural isomers.
Natural rubber is elastomer and thermoplastic. After the rubber is vulcanized, it becomes thermoset. Most of the rubber in everyday use is vulcanized to the point where it shares the nature of both; ie, if heated and cooled, it is degraded but not destroyed.
The last properties of rubber goods depend not only on polymers, but also on modifiers and fillers, such as carbon blacks, facts, whiting and others.
Biosynthesis
Rubber particles are formed in the cytoplasm of specialized latex-producing cells called laticifiers in rubber plants. The rubber particles are surrounded by a single phospholipid membrane with a hydrophobic tail pointing inwards. Membranes allow biosynthetic proteins to be sequestered on the surface of growing rubber particles, allowing new monomer units to be added from outside the biomembrane, but in lacticifiers. Rubber particles are enzymatic active entities containing three layers of material, rubber particles, biomembrane and free monomeric units. Biomembranes are held tightly to the rubber core due to the high negative charge along the double bond of the rubber polymer backbone. Free monomeric units and conjugated proteins form the outer layers. The rubber precursor is isopentenyl pyrophosphate (allyl compound), which extends with independent condensation of Mg 2 by the rubber transferase action. Monomers increase the pyrophosphate tip of the growing polymer. This process replaces the high-energy terminal pyrophosphate. The reaction produces a cis polymer. The initiation step is catalyzed by prenyltransferase, which converts the three monomers of isopentenyl pyrophosphate into farnesyl pyrophosphate. Farnesyl pyrophosphate can bind to the rubber transferase to elongate the new rubber polymer.
The required isopentenyl pyrophosphate is obtained from the mevalonate pathway, derived from acetyl-CoA in the cytosol. In plants, isoprene pyrophosphate can also be obtained from the 1-deox-D-xyulose-5-phosphate/2-C-methyl-D-erythritol-4-phosphate pathway in the plasmid. The relative ratio of the initiator unit of farnesyl pyrophosphate and the isoprenyl pyrophosphate elongation monomer determines the degree of synthesis of new particles versus the elongation of the existing particles. Although the rubber is known to be produced by only one enzyme, extracts from many latex host proteins with small molecular weights with unknown function. Proteins may function as cofactors, as the synthetic rate decreases with complete removal.
Production
Nearly 28 million tons of rubber is produced in 2013, of which about 44% is natural. Since most are synthetic, derived from petroleum, the price of natural rubber is determined, to a large extent, by the prevailing global crude oil price. Asia is the main source of natural rubber, accounting for about 94% of production in 2005. The three largest producers, Thailand, Indonesia (2.4 million tonnes) and Malaysia, account for about 72% of all natural rubber production. Natural rubber is not widely cultivated in its native continent in South America due to the presence of South American leaf blight, and other natural predators.
Cultivation
Rubber latex extracted from rubber trees. The economic life of rubber trees in the plantation is about 32 years - up to 7 years of immature phase and about 25 years of productive phase.
The soil requirement is well drained, the weathered soil consists of laterite, laterite type, sediment type, red soil or alluvial nonlaterite.
Climatic conditions for optimal growth of rubber trees are:
- Rainfall of about 250 centimeters (98Ã, in) is evenly distributed in the absence of marked dry seasons and with at least 100 rainy days per year
- Temperature range of about 20 to 34Ã, Â ° C, with monthly averages of 25 to 28Ã, Â ° C
- The atmospheric humidity is about 80%
- About 2000 hours of sunshine per year at a rate of six hours per day throughout the year
- Absence of strong winds
Many high yield clones have been developed for commercial cultivation. This clone produces more than 2,000 kg of dry rubber per hectare per year, under ideal conditions.
Collection
In places such as Kerala and Sri Lanka where coconut is in abundance, half the coconut shell is used as a collection container for latex. Glasses of pottery or aluminum or plastic cups are becoming more common in Kerala and other countries. The cups are supported by the wire that surrounds the tree. This wire combines springs so that it can stretch as the tree grows. The latex is brought into the cup by a galvanized "drain" which is struck into the bark. Tapping usually occurs in the morning, when the tree's internal pressure is highest. Good tappers can tap trees every 20 seconds on a standard half-spiral system, and the common daily "task" size is between 450 and 650 trees. Trees are usually tapped on alternate or third days, although many variations in time, length and number of pieces are used. "The tapper will make a slash on the bark with a small ax.This slant allows the latex to flow from the canal located in the outer or inner layer of bark (cambium) from the tree.Because the cambium controls the growth of the tree, growth stops if cut, a rubber beat requires accuracy, so the incision will not be too much considering the size of the tree, or too deeply, which could inhibit growth or kill it. "
It is usual to knock the pannel at least twice, sometimes three times, during the life of the tree. The economic life of a tree depends on how well the tapping is done, because the critical factor is the consumption of bark. A standard in Malaysia for alternate daily tapping is the consumption of 25 cm (vertical) bark per year. The tube containing latex in the skin rises to the spiral to the right. For this reason, cutting leads usually go up to the left to cut more tubes.
The trees drip latex for about four hours, stopping because the latex naturally clumps on the tapping piece, thus blocking the latex tube in the bark. Tappers usually rest and eat after completing their wiretapping work, then begin collecting "latex field" fluids around midday.
Field coagula
The four types of field coagules are "cuplump", "treelace", "small peasant lump" and "earth piece". Each has significantly different properties. Some trees continue to drip after collection leads to a small number of "clumps of trophies" collected at the next tapping. Latex that clumps on pieces is also collected as "tree lace". Clumps of trees and trophies converge to 10-20% of the resulting dry rubber. Latex dripping to the ground, "Earth memo", also collected periodically for processing low-grade products.
Cup bump
The cup lump is a coagulated material that is found in the collection cup when the next tapper visits the tree to knock it again. It arises from latex attached to the cup wall after the last latex is poured into the bucket, and from the latex that drips out before the latex carrier vessels from the tree become clogged. It is a higher purity and a greater value than the other three types.
Tree lace
The tree lace is a coagulum strip taken by the bugs from the previous piece before making a new piece. It usually has a higher copper and manganese content than a lump cup. Both copper and manganese are pro-oxidants and can damage the physical properties of dry rubber.
small peasant lump
Small farmer lumps are produced by small farmers who collect rubber from trees far from nearby factories. Many small Indonesian farmers, who farm in remote areas, tap trees scattered on their paths to work in the fields and collect latex (or coagulation sap) on their way home. Because it is often impossible to preserve enough sap to bring it to a factory that processes latex in time for use to create high quality products, and since latex will also be coagulated upon reaching the mill, smallholders will coagulate by whatever means are available, in any container which are available. Some small farmers use small containers, buckets, etc., but often latex is coagulated in holes in the soil, which are usually coated with plastic sheeting. Fermented acids and fruit juices are used to coagulate latex - a form of assisted biological coagulation. Little care is taken to exclude twigs, leaves, and even skin from the formed bumps, which may also include tree lace.
Earth scrap
Lumps of soil are materials that gather around the base of the tree. It arises from the sap coming out of the piece and flowing in the bark, from rain flooding the collection cup containing latex, and from the spill from the bug bucket during collection. It contains soil and other contaminants, and has variable rubber content, depending on the amount of contaminants. Ground soil is collected by a field worker two or three times a year and can be cleaned with a used washing machine to recover rubber, or sold to contractors who clean it and recover rubber. It's of low quality.
Processing
Latex clumps in a cup if stored long and must be collected before this happens. Collected latex, "latex field", is transferred into a coagulation tank for the manufacture of dry rubber or transferred into an airtight container by sieving for ammoniation. Ammoniation retains latex in a colloidal state for longer periods of time.
Latex is generally processed into a latex concentrate for the manufacture of articles immersed or coagulated under controlled and clean conditions using formic acid. The coagulated latex can then be processed into a higher-tech rubber block and is technically determined as SVR 3L or CV SVR or used to produce the Ribbed Smoke Sheet value.
The naturally coagulated rubber (cup lump) is used in the manufacture of rubber classes TSR10 and TSR20. Processing for this value is a reduction in size and cleaning process to remove contamination and prepare the material for the final drying stage.
The dried material is then removed and a pallet is made for storage and delivery.
vulcanized rubber
Natural rubber is often vulcanized, a process whereby the rubber is heated and sulfur, peroxide or bisphenol are added to enhance its durability and elasticity and to prevent it from destruction. Before World War II, black carbon was often used as a rubber additive to increase its strength, especially on vehicle tires.
Transportation
Natural rubber latex is shipped from factories in Southeast Asia, South America, and West and Central Africa to destinations worldwide. As the cost of natural rubber has increased significantly and solid rubber products, the delivery method that offers the lowest cost per unit weight is preferred. Depending on the destination, warehouse availability, and transport conditions, some methods are preferred by certain buyers. In international trade, latex rubber is mostly shipped in a 20-foot seawater. Inside the container, smaller containers are used to store latex.
Usage
Unsharpened rubber used for cement; for adhesives, insulation, and friction ribbons; and for crepe rubber used in blankets and footwear insulation. Rubberized rubber has more applications. Abrasion resistance makes softer rubber grades valuable for vehicle tires and conveyor belts, and makes valuable hard rubber for pumping and piping houses used in the handling of abrasive mud.
The flexibility of rubber pulls in hoses, tires and rollers for devices ranging from domestic presses to printing presses; its elasticity makes it suitable for different types of shock absorbers and for special engine mounts designed to reduce vibration. The nature of gas impermeability makes it useful in making articles such as air hoses, balloons, balls and cushions. The resistance of rubber to water and the action of most of the liquid chemicals has led to its use in raincoats, diving equipment, and chemical and pharmaceutical tubes, and as a coating for storage tanks, processing equipment and rail tank cars. Because of their electrical resistance, soft rubber goods are used as insulation and for protective gloves, shoes and blankets; Hard rubber is used for items such as home phone, spare parts for radio sets, meters and other electrical instruments. The high friction coefficient of rubber on dry and low surfaces on wet surface, leads to its use for the transmission of belting power and for cushions lubricated with water at deep well pumps. Indian rubber ball or lacrosse ball made of rubber.
About 25 million tons of rubber are produced each year, of which 30 percent is natural. The rest is synthetic rubber derived from petrochemical sources. The ends of latex products in latex products such as surgical gloves, condoms, balloons and other products of relatively high value. The medium range derived from technically determined natural rubber materials mostly ends in tires but also in conveyor belts, marine products, windshield wipers and other goods. Natural rubber offers good elasticity, while synthetic materials tend to offer better resistance to environmental factors such as oil, temperature, chemicals, and ultraviolet light. "Recovered rubber" is a rubber that has been aggravated and undergoes a vulcanization process to create a cross link in a rubber matrix.
Allergic reactions
Some people have serious latex allergies, and exposure to natural latex rubber products such as latex gloves can cause anaphylactic shock. The antigenic proteins found in Hevea latex can be intentionally reduced (though not eliminated) by processing.
Latex from sources Hevea , such as Guayule, can be used without an allergic reaction by people with allergies to Hevea latex.
Some allergic reactions are not to the latex itself, but from chemical residues used to speed up the cross processing. Although this may be confused with allergies to latex, it differs from that, usually taking the form of type IV hypersensitivity in the presence of traces of specific processing chemicals.
Microbial degradation
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