2020/10/19

– Shared from ecoworldonline.com

February 23, 2020

Rubber and latex are not the same thing, but many people use the words as if they are the same. Latex is the milky white sap of rubber trees, which is found beneath the bark of a mature rubber tree.

So how is rubber made and does rubber contain latex? Yes, it certainly does and we will look at the production processes of how is rubber made.

Latex is a natural substance which is harvested from plants, but it can also be artificially produced through chemical processes. Latex is often used as a synonym for rubber, but the term actually refers to a suspension of tiny polymer particles that is held in any liquid medium.

Where does Latex come from?

Although the most famous source of natural latex is the rubber tree,

it is actually found in about ten percent of all plants. Latex is a different substance as sap, and the plant creates latex as a protection against insects. If a plant is injured, it produces latex to seal themselves and thereby protecting them from attacks by insects.
Natural latex is a complex mixture of proteins, starches, sugars, resins, oils, tannin, alkaloids and gums. When it is exposed to air, it coagulates.

The Para rubber tree, Hevea brasiliensis, originally came from Brazil, but from there is was introduced to the Far East to countries like Indonesia, Malaysia, Cambodia, Vietnam, China and Burma. Most natural rubber comes from the Far East, with Thailand and Indonesia as the two leading rubber producers.

Lifespan of rubber trees in plantations is about thirty-two years. The first seven year are just growing, and then there are twenty-five productive years. Well drained soil is required and the optimum climatic conditions are:

• Rainfall of about 2500 mm per year, and with at least 100 rainy days.
• Temperature range of between 20 degrees to 34 degrees Celsius, with a monthly average temperature of 25 degrees to 28 degrees Celsius.
• Humidity level of around 80%.
• Around two thousand hours of sunshine per year, at a rate of six hours per day.
• The absence of strong winds.

So What is Rubber?

Yes, rubber is that black stuff that makes up the tires on your car or motorbike or other vehicles. The description on Wikipedia is “Natural Rubber, also called by other names of India rubber, latex, Amazonian rubber, caucho or caoutchouc, as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds, plus water.”

Rubber has been commonly used for more than a thousand years. Originally it was all made from natural sources, but now it is also synthetically or artificially produced.

Synthetic rubber was predominantly developed in Germany and the USA, due to the increased demand for rubber during the Second World War. Russia, France, Germany and the USA are still the biggest producers of synthetic rubber.

The Different Types of Rubber

There are two different types of rubber:

1. Natural Rubber is made from latex that is grown from plants. Latex is a milky, runny liquid that oozes from certain plants when you cut them. Although there are about two hundred plants that produce latex, more than 99% of the world’s natural rubber, is produced from latex that comes from a tree species called Hevea brasiliensis, or commonly known as the rubber tree or Para rubber tree. Natural rubber is also called India rubber, latex, Amazon rubber.
2. Synthetic Rubber is made from petrochemicals in chemical plants, and one of the first, and best known artificial rubbers, is neoprene. The most important synthetic rubbers in the commercial world, are Styrene Butadiene (SBR), poly acrylics, polyvinyl acetate (PVA), polyvinyl chloride (PVC), polychloroprene (also known as neoprene) and various types of polyurethane. Synthetic latex is also a liquid emulsification of polymers, but to make synthetic rubber, petroleum based products are used. Synthetic rubber is stronger and more stable than natural rubber when it comes to products like vehicle tires, so synthetic rubber is widely used in manufacturing vehicle tires. Creating synthetic rubber involves a different process and will not be covered in this post.

Harvesting Latex

Natural rubber manufacturing starts with harvesting the latex from rubber trees. The process is called “tapping” and this means scoring or cutting into the bark of the tree. To harvest latex from rubber trees, the bark is split, which allows the milky latex to seep out and be collected.

Latex then flows into a cup that is attached to the end of the cut in the tree. The process is similar to harvesting the sap from the maple tree for maple syrup.

Trees are normally “tapped” every two to three days. Latex is led into the cup or receptacle by a galvanized “spout” which is knocked into the bark.

Rubber tapping demands accuracy so that the incisions would not be too deep or too many. The rubber tree must not be killed and the growth must not be stunted. The critical factor in tree tapping is bark consumption.

The tubes in the bark that contains latex, ascends in a spiral to the right. Tapping cuts therefore usually ascends to the left, to cut through more tubes. Trees drip latex for about four hours and stops as the latex naturally coagulates on the cut. This then blocks the latex tubes in the bark.

Latex material from many trees is accumulated in large tanks.

Chemicals are added to the latex after collection to prevent it from stiffening up. To produce final natural rubber, latex goes through several processes like these: coagulation, centrifugation, compounding, vulcanization, stripping, leaching, chlorination and lubrication. More about how is rubber made will follow later.

Types of Field Coagula

Latex coagulates or solidifies quickly, so must be collected from the cups before it coagulates. The collected “field” latex is transferred into an air-tight container to preserve it in a liquid state for longer, or it is transferred into coagulation tanks for preparation of dry rubber. Ammonia is sometimes added to the latex to prevent it from solidifying.

1. Cup Lump: some trees continue to drip after the collection, leading to a small amount of coagulated material that is found in the collection cup when the tapper visits the tree again. This is high purity and more valuable than the other three types.
2. Tree Lace: latex coagulates on the tapping cut and forms a strip that the tapper peels off the previous cut before making a new cut. This has a higher manganese and copper content than cup lump. Copper and manganese are both pro-oxidants and can damage the physical properties of dry rubber.
3. Smallholder’s Lump is produced by smallholders that collect rubber from trees that are far away from factories. Smallholders who farm on paddies in remote areas, will tap the trees on the way to work in the paddy fields and collect it on their way home. By the time they return after work, the latex has coagulated and it is often impossible to preserve the latex sufficiently to be used in high quality products.
4. Earth Scrap is the material that gathers around the base of the tree. It comes from latex that overflows from the cut and runs down the bark, or rain can flood the collection cup, or it can be from tappers that spill latex during collection. This latex contains soil and other contaminants and has a variable rubber content. Earth scrap is collected two or three times per year and may be cleaned to recover the rubber., but it is low quality.

Latex vs Rubber – How is Rubber Made?

Temperature will change the natural latex. Unprocessed latex is brittle when it is cold and when it warms up, it becomes sticky and smelly. The molecules in raw latex are long chains that are tangled up and the links are weak. This means it is relatively easy to pull apart, which is why rubber is elastic and stretchy.

To turn it into a more versatile material, more processes are required and these are the basic steps:

• When latex is heated, solid chunks of crude rubber will rise to the surface of the liquid. This crude rubber is then skimmed of the surface and run through large heavy rollers. This will also remove any excess liquid. The long, thin, pressed rubber sheets are then taken to other factories to be turned into rubber products.
• Compounding adds chemicals and other additives to customize the rubber for the intended use. The formulation and method depends on the intended outcome of the fabrication process.
• Mastication: masticating machines have mechanical rollers and presses that “chew up” the raw rubber. It makes it softer, easier to work with and more sticky. After mastication, extra chemical ingredients are mixed in to improve the properties.
• Calendering is a process where the rubber is squashed into shape by rollers, or through.
• Extrusion the rubber is squeezed through specially shaped holes to make hollow tubes.
• Finally the natural rubber is vulcanized or cooked in an autoclave (an autoclave is an industrial pressure cooker). During this process, sulphur is added and the rubber is heated to about 140 degrees Celsius. Vulcanization makes rubber stronger, in that the sulfur atoms that are added, form cross-links that “bolt” the molecules together. This makes it more difficult to pull them apart, and improves the elasticity and resistance. Peroxide or bisphenol can also be added to prevent it from perishing. Vulcanization also makes rubber more stable in different temperatures.
• Fillers are also used to improve the durability and strength of rubber. Carbon black, derived from soot, is the most commonly used filler, resulting in a strong, durable, black rubber. Carbon black will increase the tensile strength of rubber and resistance to tearing and abrasion. It also increases rubber’s resistance to degradation by ultraviolet light, so is added to improve the strength of vehicle tires.

So does rubber contain latex? It certainly does, as natural rubber is made from latex.

Properties of Rubber

Rubber is strong, flexible, waterproof and a poor conductor of heat and electricity.

Some people have a serious latex allergy, but it could be the residues from chemicals that can also lead to allergic reactions, rather than the latex itself.

Soft and stretchy latex is used in products like pencil erasers, protective gloves, condoms, balloons, adhesives and paints.

Hard rubbers are used for stronger and tougher applications like inflatable boats, waterproof liners for garden ponds, heat pipes and fiber-optic cables.

Uses of Rubber

Rubber is a very versatile product, and although about fifty percent of rubber is used in vehicle tires, it also has many other diverse uses.

• Door seals on washing machines.
• Widely used in the building industry as roof and floor sealants
• Sound and vibration absorbers in window and door linings
• Elastic and rubber produced as a fiber, has excellent elongation and recovery properties, making it very important in the textile industry. Spandex, used in stretchy fabrics, is an elastomer fiber.
• Uncured rubber is used for adhesives, insulation and friction tapes.
• Vulcanized rubber has more uses, conveyor belts being on eof them.
• Flexibility means it can be used for hoses, rollers in printing presses and clothes wringers.
• Elasticity makes it suitable for shock absorbers and to reduce vibration in machine mountings.
• Rubber is impermeable to gas, which makes it useful for articles like balls, balloons, in hoses and cushions.
• Footwear like flip flop sandals and thongs. 
• Water resistant which makes it suitable to be used for diving gear, rain wear, medical and chemical tubing, linings in storage tanks, railroad tank cars and processing equipment.
• Waterproof clothes like raincoats and wellington boots and shoes, adhesives, sticky plasters.
• Outer covering of wet suits and Patagonia is producing neoprene free wet suits, made with Yulex natural rubber. .
• Electrical resistance:
  • soft rubber is used as insulation and for protective products like gloves, shoes and blankets.
  • hard rubber for electrical instruments, parts of radio sets and meters and telephone housings
• The friction coefficient of rubber is low on wet surfaces and high on dry surfaces, leading to it being used for power-transmission belting and water-lubricated bearings in deep-well pumps.
• High value items like surgical gloves, condoms and balloons are manufactured from the top end of latex production.

A wide range of bacteria can lead to degradation of natural rubber.

Rubber derived from dandelions

Dandelions grow in moderate climates and soil that might not be suitable for cultivation of food. The plant is extremely resilient and is an annual crop. Russian dandelion yields a large amount of natural rubber and could be a good alternative to the rubber tree.

The only drawback is that a huge amount of land would be required to cultivate enough dandelions to replace rubber trees.

The dandelion roots are pulverized to extract the rubber as the leaves contain very little rubber. It is an eco-friendly and sustainable crop.

Is Rubber Eco-friendly?

Natural rubber or rubber derived from trees, is eco-friendly. Harvesting the latex and using the product, has a low environmental impact and after incision, the tree heals naturally. The rubber tree is an ecologically, sustainable crop and helps to maintain the global carbon balance in the atmosphere.

There is a huge amount of rubber waste that mainly comes from discarded vehicle tires. Natural rubber can be recycled.

• Recycled rubber: Ground up used and discarded vehicle tires are used to make recycled rubber. A variety of mesh sizes are produced from the tire crumb. The product with the highest demand is for Tyre Derived Fuels or TDF’s. The build-up of rubber in landfill is eliminated by the production of this type of rubber. It has a lost cost to manufacture and has low energy requirements. It is the most economical of all rubber options. Recycled rubber is used for matting or flooring in children’s playgrounds, car components, shoe soles, mouse pads, sports bags and many more. Recycled rubber sheets also have commercial applications. These are all forms of eco-friendly rubber.
• Reclaimed rubber: this is discarded elastomer which has been de-vulcanized. This means that it can be used in a similar way to virgin materials.

New innovations with recycled rubber, are wallets made from upcycled wet suits.

Half of the world’s rubber is used to make vehicle tires, with at least half of the tires ending up in landfill, dumped or incinerated.

Synthetic rubber, which is petroleum-based elastomers, is not environmentally friendly or sustainable.

So does rubber contain latex It certainly does, but they are not the same thing.

If you have any comments on latex vs rubber, or how is rubber made, please leave them below and I will get back to you.

– Many thanks for sharing this article by Liné on ecoworldonline.com