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Flame Retardant Polythene

Polythene has a ton of beneficial properties. It’s flexible, durable, lightweight – and super affordable. It’s an amazing insulator, highly resistant to many chemicals, and has found use in just about every single facet of our lives.

Learn more about the physical properties of polythene

However, one key drawback is that polythene is flammable. And this poses a significant safety risk in a few applications. Let’s explore the reasons behind polythene’s flammability, how flame retardant additives mitigate this risk, and examine the different applications of flame retardant polythene – in packaging, construction, and other industries.


A single lick of flame on a reddish, off-black background.


Why is polythene flammable?

Polythene is essentially just the solid form of a flammable gas. 

Polythene is a type of polymer made from ethylene gas – which is a naturally flammable substance, and the simplest known alkene (a hydrocarbon with carbon–carbon double bonds). Ethylene gas is made of carbon and hydrogen atoms, which combust into CO2 and water.

Polythene is made by putting ethylene gas under immense pressure, at an immensely high temperature, which links these once free-floating carbon and hydrogen molecules into long chains. These chains clump and lock together, to make polythene the plastic we all know.

Read more – how is polythene made?

Unlike pure ethylene gas, polythene does not burn cleanly. When exposed to heat or flame, the carbon-hydrogen bonds in polythene molecules break, releasing energy and producing more complex, volatile and toxic compounds than water and CO2. The molten polythene is also hazardous, and can cause severe burns if it comes into contact with skin.

Making polythene flame retardant, especially in environments close to heat sources or sparks, is clearly a good thing. But how is it done?

How is polythene made flame retardant?

Polythene’s flammability is minimised with flame retardant additives, which can be added into the masterbatch before extrusion. The additives used are generally halogen compounds, which contain elements such as chlorine or bromine. These halogens act by disrupting the combustion process, either by inhibiting the formation of flammable gases or by interfering with the chemical reactions that sustain combustion.

Halogens are highly effective flame retardants because they release “halogen radicals” when exposed to heat or flame. These radicals effectively slow down or suppress the spread of flames by creating water as a byproduct, quenching the flames. Halogen compounds can also form a protective char layer on the surface of the polythene, which acts as a barrier to further combustion and preserves packaging or sheeting integrity for longer when exposed to heat.

The uses for flame retardant polythene

Ideally, flame retardant polythene should be used in any fire-prone application. It’s not always useful in every single packaging application – such as in part of a bag and box system, where the outer packaging is invariably going to be flammable. But it still finds widespread use in various industries, for packaging as well as within the construction sector.

In construction, flame retardant polythene is used for a range of applications, including for damp proof membranes, temporary flashings and coverings, and is even useful in general packaging for things like aggregates, which may run afoul of falling sparks.

We’ve written before about how polythene is also a highly effective material for electrical insulation – and in fact this was one of its earliest uses, during WWII and the development of radar technology.

Electrical components in automotive and aerospace industries can be separated with polythene in many ways – as a cable surround, or as a sheet that prevents short circuits between whole PCBs. Flame retardant polythene provides an added layer of protection in these applications, reducing the likelihood of electrical fires and enhancing overall electrical safety.

Flame retardant polythene finds applications in transportation, packaging, electronics – and any other sectors where fire safety is paramount. By using flame retardant additives in your own polythene packaging materials, you can enhance the safety and reliability of your products – protecting lives and property from the devastating effects of fire.

Want to create a custom, flame retardant polymer blend for your next packaging run or construction project?

Talk to our friendly team of polythene experts.

Custom polymer blends and flame retardant polythene

Order custom polythene, made to your own specs – including flame retardant polythene additives for optimal safety. Get in touch, or call us on 01773 820415 to start your order.