Rubber is one of the most popularly used products on earth. It exists in two forms – natural rubber made from plants and synthetic rubber made from chemicals. Either way, the end product is a somewhat malleable, highly durable substance that can be used in anything from tires to shoes. But is rubber a major danger to us all and could it catch fire at any instant?
Rubber is not highly flammable in that it has a high ignition temperature of 500 to 600 degrees Fahrenheit (260 to 316 Celsius). However, once rubber starts to burn, it can be very difficult to extinguish and it produces very toxic smoke that is filled with dangerous chemicals.
There are a few types of rubber with different properties and behaviors when it comes to fire. Here’s what you need to know.
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Also read: What Makes Something Flammable?
What Is Rubber?
Natural rubber (which may also be known as latex, Amazonian rubber, or India rubber) is a rubber that is formed from isoprene and water. (It may also include some minor additional chemicals in the mix).
Rubber is harvested from rubber trees and then refined into a rubber that is ready to be processed for industrial production.
It might surprise you to learn that, in theory, you could also make rubber from dandelions which produce their own latex, and a German company has demonstrated that this is commercially feasible.
Synthetic rubber is a much broader term. It refers to any polymer which is considered to be an “artificial elastomer”. They make up the bulk of the rubber market and sales of synthetic rubber, last year, were estimated to be over $50 billion globally!
The original synthetic rubber, which was used in bicycle tires, was made by Bayer in Germany in the early 1900s. Within 10-20 years many other synthetic rubbers had been developed. Mainly because of the ever-increasing market prices of natural rubber.
By the 1960s, the sales of synthetic rubber had completely overtaken the sales of natural rubber and while natural rubber is still used today – synthetic rubber is what most of us will encounter in day-to-day life.
Also read: Are Tires Flammable? You May Be Surprised…
Will It Catch On Fire?
For the moment, let’s talk about synthetic rubber, we’ll tackle natural rubber a bit later and for the sake of brevity – we’re going to call synthetic rubber, “rubber” and distinguish the other form with the word “natural” in front of it.
Synthetic rubber is not highly flammable, but it can certainly catch fire. It usually has to be heated to a fairly high temperature in order to ignite.
Once it does catch fire, rubber can sustain a flame for a very long time and be challenging to extinguish.
If you’ve ever seen one of those disturbing videos of tires burning for weeks, months or years – you will know this.
Check it out here:
Does It Burn Easily?
This is a good question and it’s hard to answer because there are so many different forms of synthetic rubber.
I’ve found a German company suggesting it will burn at 320 degrees Centigrade (608 degrees Fahrenheit) and should be considered “highly flammable”.
While the technically term for flammable is usually reserved for materials that can catch fire at low temperature, like gasoline, rubber doesn’t quite fit that criteria.
Most types of rubber will ignite around 500 to 600 degrees Fahrenheit (260 to 316 Celsius), which means that it is not easy to catch on fire.
And then other people claiming that rubber is heat-resistant and abrasion resistant and can be used for these properties.
So, what’s the truth? 600 degrees Fahrenheit is probably about the average ignition temperature of rubber and therefore, it’s not really flammable. And more to the point – depending on the thickness of the rubber, it may take several minutes for the rubber to warm through to that temperature before it will burn.
That’s because rubber is truly heat-resistant and a terrible thermo-conductor.
So, rubber does not burn easily.
What we can say though is that once it catches fire – it can be very hard to put the fire out. We’ll tackle that in a minute.
At What Temp Will It Melt?
Rubber begins to melt as it catches fire. So, at around 500 to 600 degrees Fahrenheit.
This is a problem because molten rubber can inflict horrific burns on people.
This is why it was often used as a punishment in the darkest days of Apartheid South Africa. The “offending individual” would have a burning tire hanged around their neck and they would be severely burned.
What About Natural Rubber?
Natural rubber, though it is naturally occurring, rather than made from chemicals, is quite similar to synthetic rubber, when it comes to fire.
You can see how natural rubber is harvested in this video:
Natural rubber will also ignite around 600 degrees and can sustain fire for a long time, once it starts.
How Do You Put Out A Rubber Fire?
Extinguishing a rubber fire can be very challenging.
The properties that make rubber, particularly thick rubber goods, highly combustible are the properties that make it hard to put fires out.
When rubber is burning, it can be soaked in water and the fire on the facing side of the rubber (or on the outside in case of tires) will go out. But because it has poor thermo-conducting properties, the water does not cool the rest of the rubber and it continues to burn, unseen.
Then when you stop adding water, over time, the heat from the other side returns to the side which was extinguished, and it ignites again.
This is why tire fires, for example, can burn for years. It’s not that people don’t want to extinguish them – it’s that they can’t extinguish them.
There are special firefighting agents that can be used to fight these fires, but even those are not always effective, depending on the size of the fire.
Techniques that cut off the supply of oxygen to the fire, such as smothering with sand or dirt or firefighting foam, can also be used. But the truth is that these are not always enough. And that is why these fires can burn for so long, in extreme cases.
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