The History of Rubber and Latex

History: No one knows how long rubber has been around. Men have discovered fossils of rubber-producing plants which appear to date back almost 3,000,000 years. Archeologists have dug up crude rubber balls in ruins

of Inca and Mayan civilizations in Central and South America. These are at least nine centuries old. Christopher Columbus deserves some credit for the discovery of rubber. The earliest reliable records note that the natives of Haiti played a game with a ball made from “the gum of a tree”. This report was written by a Spanish subject who accompanied Colombus on his second voyage to the New World. Portuguese historians have written that Emperor Montezuma in 1520 entertained Hernan Cortes and his soldiers in Mexico city with a game played with rubber balls. Even earlier the natives southeastern Asia knew of rubber prepared from the “juice” of a tree. They used it to make torches, and coated baskets and jars with it to make them waterproof.

In the eighteenth century two French scientists, Francois Fresneau and Charles Marie de la Condamine found new uses for rubber. These two scientists spent several years in South American on botanical research for the French academy. In 1736 they sent back to France several rolls of crude rubber, together with a description of the products fabricated from it by the people of the Amazon Valley. Fresneau called it “caoutchouc”, the French variation for “cahucho” the Indian term for “weeping tree”.

The reports described how the South Americans made shoes, battle shields, and syringe bulbs, or bottles, from the rubber, and how it was used to waterproof clothing. General scientific interest in the substance and its properties was revived.

Thirty years later, in 1770, Joseph Priestly, an English chemist at the discovery of oxygen, found that rubber could run out the marks made with a pencil. However, it is believed that someone else gave the substance it’s English name “rubber”. These two scientists spent several years in south American on botanical research for the French academy. In 1791 the first commercial application of rubber was initiated when an English manufacturer, Samuel Peal, patented a method of waterproofing cloth by treating it with a solution of rubber in turpentine. In 1820 British Industrialist Nadier produced rubber threads and attempted to use them in clothing accessories. The British inventor and chemist Charles Macintosh, in 1823, established a plant in Glasgow for the manufacture of waterproof cloth and the rainproof garments that have since borne his name.

Because the rubber then used in England came from India the term “Indian Rubber” was widely used. This term is still generally used in European countries, especially the English speaking ones. In the United States and Canada the name rubber is used alone.

NRL: Latex, milky fluid found in specialized cells, called lactiferous cells, of many higher plants. Latex, a polymer dispersed in water, contains a complex emulsion composed of varying proportions of gums, resins, tannins, alkaloids, proteins, starches, sugars, and oils. It is usually white, but in a few plants it may be yellow, orange, or red.

Latex is found in most species of the milkweed, dogbane, sapodilla, spurge, mulberry, poppy, and chicory.Many commercial gums, including rubber, balata, guayule, gutta-percha, opium, chicle, and chewing gum, are products made from refined latex. It is now also produced synthetically. The growth function of latex is not entirely understood by botanists. In some plants, latex is exuded at the site of wounds, forming a protective layer. The latex in several plants is bitter or poisonous, providing a defense against animals.

Thailand, Malaysia and Indonesia are the largest producers of natural rubber in the world.. Natural rubber comes from the Havea brasiliensis tree, which grow in tropical regions. They typically reach 20-30 meters in height on rubber plantations, and are able to produce commercial quantities of latex at about 7 years of age, depending on climate and location. The trees tend to live about 10 to 20 years, but may extend past 25 years in the hands of a skilled tapper and bark consuHavea trees are not tapped any more often than once per day, with 2 or 3 days being the norm. In countries such as Thailand, tapping usually takes place in the early hours of the morning, before dawn because the temperatures are very high and the clothing the tappers have to wear to protect them from predators is extremely hot.. Also flow rates are increased due to higher turgor pressures at these times.

A tapper uses a sharp hook shaped knife to shave a thin layer of fresh bark from the tree. This exposes the latex vesicles. The cut is typically done at 25-30° to the horizontal, as this exposes the maximum number of vesicles. The same incision is done the next day. Virgin bark is exposed first working around in panels. They may do the same thing up to seven hours later.
The thickness of the slices is extremely important to the vitality of the tree as well as the production of the latex. If you cut the slice too thick you will damage the tree and reduce the amount of product it can produce. If you cut the slices too thin it won’t produce a good amount of latex. Bark is removed in a specific area for a period of time, and then a new area is tapped allowing the tree to heal and eventually repair itself.

The latex runs down and is collected in a cup. Each tree usually produces about half a cup of latex per day and is collected later in the day. Latex will flow for approximately 1 to 3 hours after which time the vesicles become plugged with coagulum .Processing of natural rubber involves the addition of a dilute acid such as formic acid.

Then a final rolling is performed using a textured roller and the resultant rubber sheet is dried. Following this, the rubber is ready for export of further processing. This type of natural rubber accounts for about 90% of natural rubber production.Final rolling of the latex sheets using a textured roller.

Natural rubber is used in a pure form in some applications. In this case, the latex tapped from trees is concentrated using centriguges, removing water and proteinaceous materials. It is then preserved using a chemical such as ammonia.

Natural rubber is used for making products such as glue, tires, toys, shoes, condoms, gloves, catheters, balloons, some medical tubing ect. When the rubber tree dies it’s wood is used to make furniture. The tree rarely ever goes to waste and serves a meaningful purpose for it’s lifespan.

Vulcanization of Rubber: Vulcanization is the treatment of rubber to give it certain qualities like strength, elasticity, and resistance to solvents, and to render it impervious to moderate heat and cold. Chemically, the process involves the formation of cross-linkages between the polymer chains of the rubber's molecules. Vulcanization is accomplished usually by a process invented by Charles Goodyear in 1839, involving combination with sulfur and heating. A method of cold vulcanization (treating rubber with a bath or vapors of a sulfur compound) was developed by Alexander Parkes in 1846. Rubber for almost all ordinary purposes is vulcanized; exceptions are rubber cement, crepe-rubber soles, and adhesive tape.

Hard rubber is vulcanized rubber in which 30% to 50% of sulfur has been mixed before heating; soft rubber contains usually less than 5% of sulfur. After the sulfur and rubber (and usually an organic accelerator, e.g., an aniline compound, to shorten the time or lower the heat necessary for vulcanization) are mixed, the compound is usually placed in molds and subjected to heat and pressure. The heat may be applied directly by steam, by steam-heated molds, by hot air, or by hot water.

Vulcanization can also be accomplished with certain peroxides, gamma radiation, and several other organic compounds. The finished product is not sticky like raw rubber, does not harden with cold or soften much except with great heat, is elastic, springing back into shape when deformed instead of remaining deformed as unvulcanized rubber does, is highly resistant to abrasion and to gasoline and most chemicals, and is a good insulator against electricity and heat. Many synthetic rubbers undergo processes of vulcanization, some of which are similar to that applied to natural rubber. The invention of vulcanization made possible the wide use of rubber and aided the development of such industries as the automobile industry.

For years Goodyear tried to make rubber that would not be affected by temperatures. One day Goodyear accidentely spilled a mixture of rubber and sulphur on a hot stove. When he removed it he found that the rubber could be stretched and was not gummy. He found that in order to make a rubber manufacture you need to add rubber, sulphur and intense heat. In 1844 he had his discovery patented. The process was called vulcanization after Vulcan the roman god of fire.

Several other inventors helped to perfect rubber. Thomas Handcock developed a similar method of vulcanization. Nelson Gooyear perfected another way of making hard rubber. Edwin Marcus Chaffee invented the calendars used in rubber factories.

Latex Allergy: Allergy to natural rubber latex is becoming more common. Healthcare workers are especially prone to the condition, and it is in these people, and in children who have repeated surgical procedures, that the increase is occurring.
This increase is thought to be caused by the general requirement for healthcare workers to use latex gloves when patients are undergoing many treatment procedures because of the increasing prevalence of blood-borne viral diseases such as hepatitis and AIDS. Latex gloves prevent contact with other peoples body fluids.

The increase in demand for latex gloves has caused a change in the methods of manufacture and many gloves now contain more natural latex protein than before. Most adults who have become latex sensitive are either health-care workers (particularly nurses), or they are the partners of health care workers, and therefore regularly exposed to latex particles from surgical rubber gloves. It has been suggested that some babies may become sensitized from the latex gloves used by the midwife at the time of their birth.

There are two types of allergy to rubber gloves. One is an example of type I (IgE-mediated) allergy and the other is an example of type IV (contact) allergy. Type I can cause generalized allergy or even anaphylaxis and the allergy is caused by a latex protein. Type IV causes dermatitis and chemicals used in glove manufacturer are more likely to cause it than the latex itself. Vulcanized rubber, on the other hand, has numerous applications. Resistance to abrasion makes softer kinds of rubber valuable for the treads of vehicle tires and conveyor belts, and makes hard rubber valuable for pump housings and piping used in the handling of abrasive sludges.

Conclusion: The flexibility of rubber is often used in hose, tires, and rollers for a wide variety of devices ranging from domestic clothes wringers to printing presses; its elasticity makes it suitable for various kinds of shock absorbers and for specialized machinery mountings designed to reduce vibration. Being relatively impermeable to gases, rubber is useful in the manufacture of articles such as air hoses, balloons, balls, and cushions. The resistance of rubber to water and to the action of most fluid chemicals has led to its use in rainwear, diving gear, and chemical and medicinal tubing, and as a lining for storage tanks, processing equipment, and railroad 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 articles such as telephone housings, parts for radio sets, meters, and other electrical instruments. The coefficient of friction of rubber, which is high on dry surfaces and low on wet surfaces, leads to the use of rubber both for power-transmission belting and for water-lubricated bearings in deep-well pumps.

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