Most people likely think of rubber bands, tires or pencil erasers when we hear the word “rubber”. Rubber is elastic and water-resistant; it can be formulated to trap air (inner tubes) and not conduct electricity. Its most distinguishing characteristic is that it can be stretched to two, three, five, even 10 times its original length without breaking; let it go and it snaps back to its original size and shape, virtually unaltered. It can be squeezed, twisted or distorted and again, will spring back to its original shape unchanged.
Rubber consists of thousands of loosely joined molecules to make long, tangled chains. These chains of molecules can be pulled apart and untangled fairly easily, but spring back together upon release —that’s what gives rubber elastic properties.
Rubber also has astoundingly high abrasion resistance – higher than steel. It is unaffected by the corrosive action of most common chemicals and can be bonded firmly to metal as well as textiles.
For these and other reasons, rubber finds its way into tens of thousands of different products. Rubber can be formulated for applications ranging from healthcare to space travel and armaments to recreational products – everything from rubber stamps and waterproof shoes to wetsuits, hoses, gaskets, o-rings, seals, vehicle tires and artificial hearts.
There was a time when rubber came entirely from natural sources. Today however, rubber is just as likely to be made artificially, synthesized from petroleum and combined with other minerals. That’s largely because our planet can’t produce enough natural rubber to meet all of our needs.
Rubber was known to the native peoples of the Americas long before the arrival of European explorers. As early as 1525, explorers reported observing Mexican tribespeople playing with elastic balls. The first scientific study of rubber was undertaken in 1735.
It has been widely recorded that the first use for rubber was as an eraser. It was Magellan, a descendent of the famous Portuguese navigator, who suggested this use. In England, a noted 18th-century chemist credited with the discovery of oxygen, popularized rubber to the extent that it became known as “India Rubber”.
In the middle of the 20th century, a decisive historical episode irreversibly altered the state of the rubber industry. On December 7, 1941 the United States entered World War II. Three months after the attack on Pearl Harbor, the Japanese invaded Malaysia and the Dutch East Indies, desperate to take over control of natural rubber production from the allies. This gave the Axis control over 95% of world rubber supplies, plunging the United States into a “rubber” crisis.
Each Sherman tank contained a half a ton of rubber; each warship contained 20,000 rubber parts; rubber was used to coat every centimeter of wire used in every factory, home, office and military facility throughout the United States.
Unfortunately, there was not a viable, commercially produced, general purpose synthetic alternative available in the United States. To that point, American production of synthetics had been confined to relatively specialized materials with very limited production volumes. Reviewing all possible sources, at normal consumption levels, the nation had about one year’s worth of rubber stock; however these reserves also had to supply the largest and most critical industry during this period: the arms sector.
This led to the institution of a vast government program to fast track the production a general purpose synthetic material in the U.S and Canada. Ultimately, 51 government plants were constructed and began operations in North America. Within the first year of production, output of synthetic rubber tripled to 30,000 tons, increasing to more than 700,000 tons by the end of the war.
Natural rubber, also referred to as “India Rubber”, was originally derived from a milky liquid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored sap collected and refined into a usable material.
There is only one chemical type of natural rubber. The variety of physical properties found in different natural rubber products is produced entirely by different methods of plantation processing. The purified form of natural rubber is polyisoprene which can also be produced synthetically.
Natural rubber is used extensively in many applications and products. It is naturally very elastic, flexible and waterproof.
Contrarily, there are many different chemical types of synthetic rubber – each with its own advantages and disadvantages, its own spectrum of properties and its own particular area of usefulness.
It is important to understand that there is not a single type of rubber that is better than all others in an absolute sense. The choice depends on what properties are essential for a particular application. When more than one rubber can meet the requirements, certainly then price and availability would be considerations.
The earliest commercial synthetics were developed in direct response to the growing need for elastic materials with better resistance than natural rubber to oil, to heat, to sunlight and aging. Chloroprene, aka neoprene, offered improvement in all respects.
There is an exhaustive litany of mechanical, chemical, physical and specialized tests to measure specific outcomes to help you determine which rubber material best fits your specific application.
- International Institute of Synthetic Rubber Producers, Inc.
Mark Johnson is the Executive Vice President of Marketing at WARCO BILTRITE
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