Demonstrating flame resistance

Incorporating wool fibre into a new stab and flame-resistant fabric developed at AgResearch increases its flame resistance and thermal protection. The wool fabric stops burning after the flame is removed, and the char that’s left helps prevent heat from passing through the fabric to the skin.

Questions to consider:

• What is the key information needed from a flame resistance test?

• What makes wool flame-resistant? (You could follow up discussion using the interactive: Wool fibre structure and properties).

• How does wool provide thermal protection?

Transcript

Dr Stewart Collie (AgResearch)

There are a whole range of test methods for measuring the flame retardance of fabrics depending on the application it is being used for, but in most situations, you are interested in the extent to which the fabric continues to burn after a flame is removed and also the amount of heat transfer that goes through the fabric to the other side where the wearer would be. So the wool fabric performs well in both of those.

So I hold the flame against the fabric for a prolonged period of time against my hand. I'm not feeling any heat coming through yet. It’s starting to char up the wool. So that is the charred wool, and you will notice that the wool didn't actually keep burning once I'd taken the flame away. It self-extinguishes straight away. And you can see this foamy char that has built up which continues to provide that thermal protection. And we can actually brush that away, and you can just be able to make out the Vectran™ knitted structure underneath. The Vectran™ itself is flame retardant and it helps just hold that whole structure together, so it keeps providing that protection, and if I turn the fabric over, you can see there is no damage to the back at all.