A Pioneer in Rubber Band Research

The ancient Mayan People used latex to make rubber balls, hollow human figures, and as bindings used to secure axe heads to there handles and other functions. Latex is the sap of various plants, most notably the rubber tree. When it is exposed to the air it hardens into a springy mass. The Mayans learned to mix the rubber sap with the juice from morning glory vines so that it became more durable and elastic, and didn’t get quite as brittle. Both the rubber tree and the morning glory were important plants to the Mayan people – the latter being a hallucinogen as well as a healing herb. They two plants tended to grow close together. Combining their juices, a black substance about the texture of a gum-type pencil eraser was formed. Native peoples in the region still make rubber in the same way. 

Vulcanized rubber –  The Beginning of Rubber

In 1736 several rolled sheets of rubber were sent to France where it fascinated those who saw it. In 1791, an Englishman named Samuel Peal discovered a means of waterproofing cloth by mixing rubber with turpentine. English inventor and scientist, Joseph Priestly, got his hands on some rubber and realized it could be used to erase pencil marks on sheets of paper. 

Thomas Hancock was an English inventor who founded the British rubber industry. He invented the masticator, a machine that shredded rubber scraps, allowing rubber to be recycled after being formed into blocks or rolled into sheets. In 1820, Hancock patented elastic fastenings for gloves, suspenders, shoes and stockings. In the process of creating the first elastic fabrics, Hancock found himself wasting considerable rubber. He invented the masticator to help conserve rubber. The first masticator was a wooden machine that used a hollow cylinder studded with teeth – inside the cylinder was a studded core that was hand cranked. In 1821, Hancock joined forces with the Scottish chemist and inventor of waterproof fabrics, Charles Macintosh. Together they produced Macintosh coats, or Mackintoshes, named after Charles Macintosh. 

In 1823, Charles Macintosh patented a method for making waterproof garments by using rubber dissolved in coal-tar naphtha for cementing two pieces of cloth together. While he was trying to find uses for the waste products of gasworks, Macintosh discovered that coal-tar naphtha dissolved India rubber. He took wool cloth and painted one side with the dissolved rubber preparation and placed another layer of wool cloth on top. 

In 1837, Hancock finally patented the masticator, when Macintosh’s waterproofing patent was being challenged. In the pre-Goodyear and pre-vulcanization age of rubber age, the masticated rubber that Hancock invented was used for pneumatic cushions, mattresses, pillows and bellows, hose, tubing, solid tires, shoes, packing and springs. It was used everywhere. Hancock became the largest manufacturer of rubber goods in the world. The wooden masticator turned into a steam-driven metal machine, used to supple the Macintosh factory with masticated rubber. 

This created the first practical waterproof fabric, but the fabric was not perfect. It was easy to puncture when it was seamed, the natural oil in wool caused the rubber cement to deteriorate. In cold weather the fabric became stiffer and in hot weather the fabric became sticky. When vulcanized rubber was invented in 1839, Macintosh’s fabrics improved since the new rubber could withstand temperature changes. 

Charles Goodyear, an American whose name graces the tires under millions of automobiles, is credited with the modern form of rubber. Before 1839, rubber was subject to the conditions of the weather. If the weather was hot and sticky, so was the rubber. In cold weather it became brittle and hard. Goodyear’s recipe, a process known as vulcanization, was discovered when a mixture of rubber, lead and sulfur were accidentally dropped onto a hot stove. The result was a substance that wasn’t affected by weather, and which would snap back to its original form if stretched. The process was refined and the uses for rubber materials increased as well. This new rubber was resistant to water and chemical interactions and did not conduct electricity, so it was suited for a variety of products. The process of making the rubber product improved as time went by, and now various chemicals are added before the mix is poured into molds, heated and cured under pressure. 

But who invented the rubber bands? 

On March 17, 1845, Stephen Perry of the rubber manufacturing company Messers Perry and Co, Rubber Co Manuf London patented the fist rubber bands made of vulcanized rubber. Perry invented the rubber band to hold papers or envelopes together. 

At the present time Antoon Versteegde uses the same kind of rubber bands to fasten the bamboo poles in his transient constructions. 

Rubber tapping 

Latex (a natural, stretchy substance from which rubber is made) is extracted from rubber trees. Rubber trees are large trees (belonging to the spurge family, family Euphorbiaceae) that live in tropical (warm) areas. These trees are tapped for their latex, which is produced in their bark layers (latex is not the sap). The Pará rubber tree (Hevea brasiliensis) is native to South American rain forests, and grows to be over 30 m tall. 

In 1876, an Englishman named Sir Henry Wickham collected about seventy thousand rubber tree seeds from the Para rubber tree (taken from the lower Amazon area of Brazil) and brought them to London, England. Seedlings were grown in London, and later sent to the East Indies, Ceylon and Singapore, where he started rubber plantations. The technique of tapping rubber trees for their latex was developed in Southeast Asia (before that, the trees were cut down to extract the rubber). Commercial rubber production now takes place in Malaysia, Thailand, Indonesia, and Sri Lanka (but not significantly in South America). 

In 1877 an American named Chapman Mitchell learned to recycle used rubber into new products. 

Modern rubber 

Today about three quarters of the rubber in production is a synthetic product made from crude oil. World War II cut the United States off from rubber supplies worldwide, and they stepped up production of synthetic rubber for use in the war effort. There are about 20 grades of synthetic rubber and the intended end use determines selection. In general, to make synthetic rubber, byproducts of petroleum refining called butadiene and styrene are combined in a reactor containing soapsuds. A milky looking liquid latex results. The latex is coagulated from the liquid and results in rubber “crumbs” that are purchased by manufacturers and melted into numerous products. 

There is only one kind of natural rubber. Because the rubber plant only thrives in hot, damp regions near the equator, so 90% of true rubber production today occurs in the Southeast Asian countries of Malaysia and Thailand and in Indonesia. Indonesia’s production has dropped in recent years and new plantations were started in Africa to take up the slack.

Source – http://www.versteegde.nl/History_of_Elastic_and_Rubber_Bands.html

Expensive and exhibit best rubber properties in India, Thailand, Vieatnam and Malaysia

When it comes to dip molding products with emulsions of liquid rubber, it is necessary to complete a series of process steps to assure proper formation, vulcanization and finish treatment to meet the customer’s needs in the final application. 

Dip molding can enable the creation of products in a variety of shapes, sizes and wall thicknesses, including rubber bands probe covers, bellows, neck seals, surgeon gloves, heart balloons and other unique parts. 

Natural rubber has outstanding resilience and high tensile strength but also carries a protein that can cause an allergic reaction in humans. Synthetic neoprene and synthetic polyisoprene, in contrast, are non-allergenic. Neoprene stands up against a multitude of factors; it’s resistant to flame, oil (moderate), weather, ozone cracking, abrasion and flex cracking, alkalis and acids. Polyisoprene is a close replacement to natural rubber when it comes to feel and flexibility, with better resistance to weather than natural rubber latex. Polyisoprene, though, does sacrifice some tensile strength, tear resistance and compression set. 

The term “dipping” is associated with the manipulation of the dip form. In fact, the forms are dipped into the materials as the sequence is performed. It is important to ensure rubber recipes meet FDA medical device guidelines and requirements. 

Here’s what the process looks like: 

The dipping process can be characterized as a conversion sequence: The rubber is converted from a liquid to a solid and then chemically converted into a vulcanized network of molecules. More importantly, the chemical process converts the rubber from a very fragile film into a networked group of molecules that can stretch and deform – and still return to their original shape. 

Coagulation: Changing a liquid to a solid 
The coagulation process is not always necessary for all “dip” processing but is critical to our processing sequence. The rubber can be allowed to change from a liquid to a solid through air drying, but that will take much time. Some-thin walled parts are produced in this manner. The coagulation process uses chemicals to force this physical state change. 

The coagulant is a mixture or solution of salts, surfactants, thickeners and release agents in a solvent, typically water. Alcohol can also be used as the solvent in some processes. Alcohol evaporates quickly and leaves very little residue. Some water-based coagulants will require help from an oven or other means to dry the coagulant.

The main component of the coagulant is the salt (calcium nitrate), an inexpensive material that provides the best uniformity of coagulation over the dip form. 

Surfactants are used to wet out the dip form and assure a smooth, uniform coating of coagulant onto the form. 

Release agents such as calcium carbonate are used in the coagulant formula to aid in the removal of the cured rubber part from the dip form. 

Keys to coagulant performance include uniform coating, fast evaporation, material temperatures, entrance and retrieval speeds, and easy change or maintenance of the calcium concentration. 

The rubber dipping step 
This is the stage in which the rubber is converted from a liquid to a solid. The chemical agent which facilitates the solidification, the coagulant, is now applied to the dip form and is dry. 

The form is “dwelled,” or held immersed in the tank of liquid rubber. As the rubber makes physical contact with the coagulant, the calcium from the coagulant causes the rubber to destabilize and turn from a liquid state to a solid state. The longer the form is immersed, the thicker the wall will develop. This chemical reaction will continue until all the calcium is consumed from the coagulant. 

Keys to latex dipping include entrance and exit speeds, temperature of the latex, uniformity of coagulant coating, and controlling pH, viscosity and total solids of the rubber. 

The leach dip 
The leach process is the most effective stage to remove unwanted, water-based chemicals which are not wanted in the final product. The most opportune time to remove the unwanted materials from the dipped film is the leach before cure. 

What is removed? The leach process removes residual salts, surfactants and water based proteins. 

Main material components include the coagulant (calcium nitrate) and rubbers (natural (NR); neoprene (CR); polyisoporene (IR); nitrile (NBR)). Inadequate leaching can result in “sweating,” a sticky film on the finished product, as well as adhesion failure and increased risk of allergic reactions. 

The keys to leaching performance include water quality, water temperature, dwell time ad water flow rate. 

Cure stage 
This step is a two-step activity. The water in the rubber film is being removed and the temperature of the oven along with time is activating the accelerators starting the cure or vulcanization process. Cure time and cure temperature are key when it comes to optimizing the best physical properties of the different types of rubbers. 

Finish 
Several options are available to treat the surface of a dipped part so that the part does not stick to itself. Options include a powder part, urethane coating, silicone rinse, chlorination and soap wash. This is about what the customer wants or needs for their product to be successful.

Source – https://www.medicaldesignandoutsourcing.com/dip-molding-medical-device-products-need-know/

Very high production rate and less expensive. Most common method used around the world. 

Rubber bands are one of the most convenient products of the twentieth century, used by numerous individuals and industries for a wide variety of purposes. The largest consumer of rubber bands in the world is the U.S. Post Office, which orders millions of pounds a year to use in sorting and delivering piles of mail. The newspaper industry also uses massive quantities of rubber bands to keep individual newspapers rolled or folded together before home delivery. Yet another large consumer is the agricultural products industry. The flower industry buys rubber bands to hold together bouquets or uses delicate bands around the petals of flowers (especially tulips) to keep them from opening in transit. Vegetables such as celery are frequently bunched together with rubber bands, and the plastic coverings over berries, broccoli, and cauliflower are often secured with rubber bands. All in all, more than 30 million pounds of rubber bands are sold in the United States alone each year. Rubber, which derives from plants that grow best in an equatorial climate, was first discovered by European explorers in the Americas, where Christopher Columbus encountered Mayan indians using water-proof shoes and bottles made from the substance. Intrigued, he carried several Mayan rubber items on his return voyage to Europe. Over the next several hundred years, other European explorers followed suit. The word rubber was born in 1770, when an English chemist named Joseph Priestley discovered that hardened pieces of rubber would rub out pencil marks. By the late eighteenth century, European scientists had discovered that dissolving rubber in turpentine produced a liquid that could be used to waterproof cloth. 

However, until the beginning of the 19th century, natural rubber presented several technical challenges. While it clearly had the potential for useful development, no one was able to get it to the point where it could be used commercially. Rubber rapidly became dry and brittle during cold European winters. Worse, it became soft and sticky when warn. 

The American inventor Charles Goodyear had been experimenting with methods to refine natural rubber for nearly a decade before an accident enabled him to overcome these problems with unprocessed rubber. One day in 1839, Goodyear accidentally left a piece of raw rubber on top of a warm stove, along with some sulfur and lead. On discovering his “mistake,” Goodyear delightedly realized that the rubber had acquired a much more usable consistency and texture. Over the next five years, he perfected the process of converting natural rubber into a usable commodity. This process, which Goodyear dubbed vulcanization after the Roman god of fire, enabled the modern rubber industry to develop. 

The first rubber band was developed in 1843, when an Englishman named Thomas Hancock sliced up a rubber bottle made by some New World Indians. Although these first rubber bands were adapted as garters and waistbands, their usefulness was limited because they were unvulcanized. Hancock himself never vulcanized his invention, but he did advance the rubber industry by developing the masticator machine, a forerunner of the modern rubber milling machine used to manufacture rubber bands as well as other rubber products. In 1845, Hancock’s countryman Thomas Perry patented the rubber band and opened the first rubber-band factory. With the combined contributions of 

After the latex has been harvested and purified, it is combined with acetic or formic acid to form rubber slabs. Next, the slabs are squeezed between rollers to remove excess water and pressed into bales or blocks, usually 2 or 3 square feet. The rubber is then shipped to a rubber factory, where the slabs are machine cut into small pieces and mixed in a Banbury mixer with other ingredients—sulfur to vulcanize it, pigments to color it, and other chemicals to increase or diminish the elasticity of the resulting rubber bands. After being milled, the heated rubber strips are fed into an extruding machine that forces the rubber out in long, hollow tubes. 
After the latex has been harvested and purified, it is combined with acetic or formic acid to form rubber slabs. Next, the slabs are squeezed between rollers to remove excess water and pressed into bales or blocks, usually 2 or 3 square feet. 
The rubber is then shipped to a rubber factory, where the slabs are machine cut into small pieces and mixed in a Banbury mixer with other ingredients—sulfur to vulcanize it, pigments to color it, and other chemicals to increase or diminish the elasticity of the resulting rubber bands. After being milled, the heated rubber strips are fed into an extruding machine that forces the rubber out in long, hollow tubes. 
Goodyear, Hancock, and Perry, manufacturing effective rubber bands became possible. 
In the late nineteenth century, British rubber manufacturers began to foster the development of rubber plantations in British colonies like Malaya and Ceylon. Rubber plantations thrived in the warm climate of Southeast Asia, and the European rubber industry thrived as well, because now it could avoid the expense of importing rubber from the Americas, which lay beyond Britain’s political and economic control. 

Raw Materials 
Although 75 percent of today’s rubber products are made from the synthetic rubber perfected during World War II, rubber bands are still made from organic rubber because it offers superior elasticity. Natural rubber comes from latex, a milky fluid composed primarily of water with a smaller amount of rubber and trace amounts of resin, protein, sugar, and mineral matter. Most non-synthetic industrial latex derives from the rubber tree (Hevea brasiliensis), but various equatorial trees, shrubs, and vines also produce the substance. 

Within the rubber tree, latex is found between the external bark and the Cambium layer, through which the tree’s sap flows. Distinct from the sap, latex serves as a protective agent, seeping out of and sealing over wounds in the tree’s bark. To “tap” the substance, rubber harvesters cut a “V”-shaped wedge in the bark. They have to be careful to make their cuts at a depth of between .25 and .5 inch (.635 and 1.2 centimeters) in a mature tree (7 to 10 inches or 17.7 to 25.4 centimeters in diameter), because they must reach the latex without cutting into the sap vessels. They must also take care to tap each tree in a slightly different place every time. At the end of the nineteenth century botanist Henry Ridley began recommending this measure, having noted that repeated tapping in the same 

After being extruded, the rubber tubes are forced over aluminum poles called mandrels and cured in large ovens. Finally, the tubes are removed from the mandrels and fed into a cutting machine that slices them into finished rubber bands. 
After being extruded, the rubber tubes are forced over aluminum poles called mandrels and cured in large ovens. Finally, the tubes are removed from the mandrels and fed into a cutting machine that slices them into finished rubber bands. 
spot swiftly killed rubber trees. After workers make a cut, latex oozes out and collects in a container attached to the tree. Tapping takes place every other day, and each tapping yields about 2 ounces (56 grams) of the substance. After tapping, the cut dries, and latex stops flowing in an hour or two. 

The Manufacturing Process 
Processing the natural latex 
1 The initial stage of manufacturing the harvested latex usually takes place on the rubber plantation, prior to packing and shipping. The first step in processing the latex is purification, which entails straining it to remove the other constituent elements apart from rubber and to filter out impurities such as tree sap and debris. 
2 The purified rubber is now collected in large vats. Combined with acetic or formic acid, the rubber particles cling together to form slabs. 
3 Next, the slabs are squeezed between rollers to remove excess water and pressed into bales or blocks, usually 2 or 3 square feet (.6 or .9 square meter), ready for shipping to factories. The size of the blocks depends on what the individual plantation can accommodate. 
Mixing and milling 
4 The rubber is then shipped to a rubber factory. Here, the slabs are machine cut (or chopped) into small pieces. Next, many manufacturers use a Banbury Mixer, invented in 1916 by Femely H. Banbury. This machine mixes the rubber with other ingredients—sulfur to vulcanize it, pigments to color it, and other chemicals to increase or diminish the elasticity of the resulting rubber bands. Although some companies don’t add these ingredients until the next stage (milling), the Banbury machine integrates them more thoroughly, producing a more uniform product. 
5 Milling, the next phase of production, entails heating the rubber (a blended mass if it has been mixed, discrete pieces if it has not) and squeezing it flat in a milling machine. 
Extrusion 
6 After the heated, flattened rubber leaves the milling machine, it is cut into strips. Still hot from the milling, the strips are then fed into an extruding machine which forces the rubber out in long, hollow tubes (much as a meat grinder produces long strings of meat). Excess rubber regularly builds up around the head of each extruding machine, and this rubber is cut off, collected, and placed back with the rubber going into the milling machine. 
Curing 

7 The tubes of rubber are then forced over aluminum poles called mandrels, which have been covered with talcum powder to keep the rubber from sticking. Although the rubber has already been vulcanized, it’s rather brittle at this point, and needs to be “cured” before it is elastic and usable. To accomplish this, the poles are loaded onto racks that are steamed and heated in large machines. 
8 Removed from the poles and washed to remove the talcum powder, the tubes of rubber are fed into another machine that slices them into finished rubber bands. Rubber bands are sold by weight, and, because they tend to clump together, only small quantities can be weighed accurately by machines. Generally, any package over 5 pounds (2.2 kilograms) can be loaded by machine but will still require manual weighing and adjusting. 

Quality Control 
Sample rubber bands from each batch are subjected to a variety of quality tests. One such test measures modulus, or how hard a band snaps back: a tight band should snap back forcefully when pulled, while a band made to secure fragile objects should snap back more gently. Another test, for elongation, determines how far a band will stretch, which depends upon the percentage of rubber in a band: the more rubber, the further it should stretch. A third trait commonly tested is break strength, or whether a rubber band is strong enough to withstand normal strain. If 90 percent of the sample bands in a batch pass a particular test, the batch moves on to the next test; if 90 percent pass all of the tests, the batch is considered market-ready. 

Source – http://www.madehow.com/Volume-1/Rubber-Band.html#ixzz59A8Z6xGbVery high production and less expensive. Most common method used around the world.