Rubber Tapping and Coagulation

A milky liquid comes out of the wound when the bark of the Hevea tree is partially cut through (tapped), and it dries to form a rubbery film. The biological function of this is still unknown: it could aid wound healing by protecting the inner bark, or it could have other biochemical functions. The Latex is comprised of an aqueous suspension of very small particles, up to 0.5 micrometre in diameter, of cis-polyisoprene, a linear rubbery polymer with a high molecular weight. The suspension’s rubber content is up to 30%.

About Rubber Trees

Let us look at the process of rubber chemical compound tapping and coagulation.

Rubber trees can be tapped around once every two days, yielding a cupful of l that contains nearly 50 grams (1.7 ounces) of solid rubber every single time. The traditional method of tapping is to score the tree with a knife for half of the circumference of the trunk, slanting the cut down from the highest point, which is convenient to the tapper, at an angle of 30° from left to right. Every subsequent cut can be made immediately below its predecessor.

Following a time of hard tapping, trees are often resting. When a tree is 5 or 6 years old, the production commences; with care, the useful life of the tree may extend to more than 20 years. With the trees cultivated at a density of 375 per one hectare (150 per acre), nearly 2,500 kg of rubber may be produced per hectare per one year (it means nearly one ton per acre per one year).

The below figure shows Latex, which is being extracted from a rubber tree:

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After the collection of tapped Latex, rubber can be recovered from the process of emulsion by coagulation with formic acid by creating crumbs, which resemble curds of milk. The crumbs are washed and then dried between the rolls and compacted into blocks 67 by 33 by 18 cm (it means 26 by 13 by 7.5 inches) in size and weighing about 33.3 kg (or 73 pounds). Then, the blocks are wrapped in polyethylene sheets and, after that, packed into one-ton crates for shipping.

The below figure represents the sheets of natural rubber, which is coagulated from Latex being passed between rollers:

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Another production of rubber is as a smoked sheet, where the coagulum can be pressed into thin sheets, which are washed and, after that, dried over a smoky wood fire. Natural fungicides in the smoke protect against mould growth and give the smoke its distinctive amber colour. Dried sheets are then packed into 110-kg (or 250-pound) bales for shipping.

In the figure given below, the sheets of natural rubber are hung from the racks in a smoke room for final drying:

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Latex is made from about 10% of all-natural rubber, concentrated to a rubber content of about 60%, and used to make dipped products like surgical gloves, prophylactics, and toys.

Development of the Natural Rubber Industry

If the Latex is allowed to naturally evaporate, the rubber film that forms can be dried and pressed into useful items like shoes, balls, and bottles. Indians who are living in South America made such objects in early times: for instance, rubber balls were used in an Aztec ceremonial game (known as ollama) long prior to Christopher Columbus exploring the Caribbean and South America.

Columbus is known to have seen natives in present-day Haiti playing a game with balls made from the tree's gum during his second voyage to the New World in 1493–96. In 1615, a Spaniard related how the Indians, having gathered the milk from the incisions made in different trees, brushed it onto their cloaks and also obtained the bottles and crude footwear by coating the earthen molds and allowing them to dry.

Charles-Marie de La Condamine, a member of a French geographic expedition sent to South America in 1735, gave the first serious accounts of rubber production and the primitive Native American system of manufacture in the 18th century. La Condamine has described “caoutchouc” (as the French spelling of a native word for “weeping wood”) as the Hevea tree’s condensed juice, and after that, in 1736, he sent rubber samples to Europe.

At first, the new material was merely a scientific curiosity. After a British scientist named Joseph Priestley commented on its utility for scraping pencil marks from paper a few years later, the word "rubber" was coined. Gradually, other applications developed, notably for clothing and waterproofing shoes.

Essential progress toward a true rubber industry came out at the beginning of the 19th century from the separate experiments of an English inventor named Thomas Hancock and a Scottish chemist named Charles Macintosh. The contribution of the macintosh was the rediscovery, in 1823, of coal-tar naphtha as an effective and cheap solvent. And, he placed the solution of rubber and naphtha between the two fabrics and, in so doing, avoided the sticky surfaces that had been quite common in earlier single-texture garments that are treated with rubber. The manufacturing of these double-textured waterproof cloaks henceforth referred to as “mackintoshes,” began soon afterwards.