An international standard, ISO 2921:2019 – Rubber, Vulcanized – Determination Of Low-Temperature Characteristics – Temperature-Retraction Procedure (TR Test), helps test vulcanized rubber.
Vulcan is the Roman god of fire, metalworking, and the forge. He’s even where we get the word “volcano”— the Italian volcano derives from the Latin Vulcanus. His counterpart in the Greek pantheon, Hephaestus, shares many striking similarities, but is unique in his lack of mobility. To aid him in his workshop, Hephaestus created automatons—robots.
The process performed to fortify rubber and make it heat-resistant—vulcanization—derives its name from a Roman god whose alternative essentially, according to legend, created machinery, a typical companion to vulcanized rubber. In fact, vulcanized rubber typically comprises tires, as well as sticking plasters, apparel, and adhesives.
Among several strengthened qualities, vulcanized rubber is able to retain its elasticity across a spectrum of temperatures. To help assure this quality, ISO 2921:2019 outlines specific temperature-retraction testing of vulcanized rubber.
What is Vulcanized Rubber?
Vulcanized rubber is marked by a few key characteristics: high strength, elasticity, durability, and waterproofness, which are granted through a chemical process. This process, vulcanization, takes place when rubber is heated with a curing ingredient, typically sulfur.
While rubber today is often imbued with these qualities, that was not always the case. Back in the mid-1800s, rubber was praised for its versatility, even being labeled as a wonder material. Unfortunately, rubber was only a marvel for half the year—in the summer, it melted, and, in the winter, it cracked.
Charles Goodyear set out to remedy this issue. Putting his family in debt and his own health on the line, Goodyear eventually combined rubber and sulfur together on a hot stove by accident. Following a tireless, decade-long process, in 1844, he patented the vulcanization process.
Today, thanks to this discovery, vulcanized rubber has become exceedingly prominent, deriving both naturally from the rubber tree and from artificial sources.
What is ISO 2921:2019?
To test the temperature-retraction characteristics of stretched vulcanized rubber, while following ISO 2921:2019, a test piece is stretched at standard laboratory temperature, then cooled to a low temperature. Once the stretching force is removed, the process involves increasing the temperature at a uniform rate. This allows the user to determine the temperatures at which specified percentage retractions occur.
Users should note that ISO 2921:2019 does not cover thermoplastic rubbers, since many thermoplastic elastomers have a yield point in the range of 5% to 20% elongation.
ISO 2921:2019 – Rubber, Vulcanized – Determination Of Low-Temperature Characteristics – Temperature-Retraction Procedure (TR Test) is available on the ANSI Webstore.