Natural Rubber: A Product with a Thousand Uses

Derived from the latex of the rubber tree, it is utilized in the production of a wide array of common items.

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By Max Bender

rubber

Rubber is a 100% natural material extracted from the latex produced by certain plants commonly referred to as rubber trees. Its processing has been carried out for centuries and is an environmentally friendly process, which is why it is still considered a 100% ecological material today (of course we are talking about natural rubber).

Rubber: What Is It?

Rubber is 100% natural rubber. It is derived from the processing of latex obtained by incising the bark of a tree typical of the Amazon, the Hevea brasiliensis.

Rubber is an elastomer: a polymeric material of natural or synthetic origin characterized by great elasticity, meaning its ability to deform significantly when subjected to an external force and then return to its original shape.

Much of the use of this natural product today has been replaced with synthetic rubbers produced by industrial processes that allow the production of products with equivalent performance but at a significantly lower cost.

History of Rubber

Production was for years a unique prerogative of the Amazon Basin, a source of great wealth. This was one of the reasons why many Europeans speculated on cultivations in Brazilian plantations.

Natural rubber was already known in Europe by the mid-19th century, but it came solely from plantations in South America. Only in the 20th century were plantations also established in Southeast Asia, where the humid climate was favorable.

The invention of vulcanization was crucial for its widespread use. Its invention is usually credited to the American Charles Goodyear and dates back to 1844.

The latex, without this process, is unusable because it is sticky when exposed to sunlight, melts at high temperatures, is fragile at low temperatures, and turns brown and coagulates when exposed to air.

Until a few decades ago, it represented the only rubbery and elastic material on the market.

Rubber Tree

Hevea brasiliensis belongs to the Euphorbiaceae family, which includes about twenty species. It is widespread in northern Brazil, especially in the Amazon region.

The tree reaches a height of 10 meters, with apetalous flowers and leaves measuring 5-6 cm in length, but the most important characteristic of the plant is the presence of latex in the lactiferous vessels of the bark and in the liberian zone.

From the latex that flows when the bark of the tree is incised, para is obtained, which is the basis of natural rubber production.

In these tree plantations, 200-250 trees are cultivated per hectare, in order to obtain an annual yield of almost 450 kg of latex per hectare.

Processing of Liquid Rubber

After harvesting, the liquid rubber is filtered, diluted with water, and then mixed with some substances that improve mechanical resistance and abrasion resistance. In particular, carbon black is often used (hence the black color of rubber products). If a black color is to be avoided, white additives such as precipitated silica, clay, or precipitated gypsum are used.

These chemical treatments modify its structure, making it durable and elastic, as it is initially a material that is very sensitive to temperature changes and light:

  • It softens with heat
  • It stiffens with cold
  • The color changes when exposed to direct light

Vulcanization

To stabilize natural rubber and make it more durable, a process called sulfur vulcanization is carried out. It was introduced in 1840, so it’s old technology.

The costs of processing natural rubber are high, which is why in recent years, the consumer products industry has increasingly chosen to use synthetic rubber, almost completely replacing natural and ecological rubber.

rubber

Synthetic Rubber

The sudden shortage of raw materials at the end of the war highlighted both the economic and political importance of natural rubber and stimulated research into alternative products, particularly synthetic rubber.

The first synthetic rubbers produced were polyisoprene in Germany in 1909 and polybutadiene in Russia in 1910. The invention of styrene-butadiene rubber by German chemists in 1935 was also important.

With the advent of chemical industries in the 1960s, numerous synthetic rubbers were introduced to the market.

Synthetic rubbers, created to replace natural rubber by lowering production costs and using large-scale industrial processes, are very durable over time but are not biodegradable.

Biodegradable Rubber

Natural latex is inherently biodegradable and environmentally safe, but the substances with which it is treated, such as ammonia and tetramethylthiuram disulfide, and zinc oxide as a preservative against bacterial decomposition, make it difficult to recycle.

In fact, wastewater treatment plant operators report that latex is one of several problematic materials not affected by biological treatment systems.

Therefore, products made from it are difficult to recycle. At present, no technique has been found to reuse them while preserving all their qualities. However, it can be used to make less elastic products with lower purity requirements.

For example, flexible pavements made from recycled bitumen compared to regular ones are more flexible at low temperatures and more resistant to high temperatures.

Additionally, it can also be used as fuel in cement factories and some power plants, and the “dust” made from recycled rubber granules, especially from used tires, is used to improve the appearance, flexibility, and stability of artificial turf fields.

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