Plastic materials in general are excellent insulators. Combined with their high mechanical strength and low weight, they are particularly suitable for the electric and electronics (E&E) market as well as the transportation and appliances industries. One commonly used plastic material for this application is from the polyamide family.
However, these materials can catch fire when close enough to an ignition source like an electric spark. One measure to ensure fire safety is the addition of flame retardants (FR).
In general, a low amount of flame retardant is desired to have the least effect on the plastic’s properties and processing behavior. Like any additive, flame retardants increase the viscosity of polymer melts, which is especially critical in the electronics industry where miniaturization and thus very thin walls are standard.
Initiated by only one electric spark, even a starting fire develops smoke. The toxicity and corrosiveness of smoke often observed comes from halogenated polymers or flame retardants. For that reason, special non-halogenated flame retardants and graphite-based flame retardants are used to eliminate these problems.
The TCC 918 Cone Calorimeter saves lives!
Fire testing regulations are crucial in keeping flammability and the spread of fire at a manageable level. The “Reaction to Fire Test” in accordance with International Standard ISO 5660-1 and ASTM E1354 uses a Cone Calorimeter to assess the heat release rate and dynamic smoke production of a material sample. The Cone Calorimeter is also essential in determining the fire safety of newly developed materials.
How different flame retardants influence fire behavior
To study the effect of different non-halogenated flame retardants on the fire behavior of PA 6, samples of the different compounds were injection molded into 100 x 100 x 4 mm3 plates and tested in the TCC 918.
For neat PA 6, PA 6 with graphite based flame retardant and PA 6 with non-halogenated flame retardant the mass loss, heat release rate and transmission as a function of time were investigated (Figure 2).
It can be seen that the PA6 sample with 20 wt% graphite-based flame retardant (red curve) shows the lowest mass loss, heat release and smoke release (lowest reduction in transmission) of all samples. In comparison, the sample with 20 wt% non-halogenated flame retardant (green curve) behaves very similarly to the neat PA 6 material (blue curve). In the case of the heat release, it shows slightly lower values and the heat release ends earlier. In the case of transmission, however, the smoke emission is much higher than for the neat PA 6.
This shows that in the case of this particular PA6 as well as the investigated FR loadings, the graphite-based flame retardant performs much better and significantly reduces the detrimental effects a fire can have on its surroundings.
More about the sample preparation and test setup will be available in a new application note soon! Stay informed and subscribe to our newsletter!