How Rubber Bands Are Manufactured?
Rubber bands start of life as blocks of spongey-type material that’s basically just sap from rubber trees. For some reason, they dye it yellow, too. After the rubber has been formed into a dough, there’s loads of other bizarre processes it has to go through before it evolves into a band.
The manufacturing process starts with processing natural latex – Impurities such as tree sap and debris are filtered out and combined with acetic or formic acid to form slabs. The slabs are squeezed between rollers to remove water and pressed into bales or blocks usually 2 or 3 square feet.
Then comes the mixing and milling – Slabs are machine cut into small pieces. Using a banbury mixer the rubber is mixed with other ingredients: sulfur to vulcanize, pigments to color, and chemicals to adjust the required elasticity of the rubber bands. Milling entails heating the rubber and squeezing it flat in a milling machine.
In the next step extrusion takes place – Rubber sheets are cut into strips. Still hot from the milling, the strips are fed into an extruding machine which forces the rubber out in long, hollow tubes to form into a tube shape.
Then comes the curing – 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.
In this step cutting takes place – Removed from the poles and washed to remove the talcum powder, the tubes of rubber are fed into another machine that slices them into “rings” that are finished rubber bands.
Final step includes quality control check- 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.