Engineering plastics – The Manual - F.wood-supply.dk

Flame retardant classification
With regard to flame retardant classification, a variety of
characteristics are of relevance. Combustibility is defined
as the chemical property of materials to react with oxygen
while emitting radiant energy. Only combustible materials
are able to burn.
Flammability is another important property of a material.
Most organic compounds are combustible on the direct application
of energy. However, some plastics, in particular
high-performance plastics, are flame retardant by their nature
or inherently self-extinguishing, making them suitable
for use where fire protection is an issue.
There are various standards available which classify the
combustibility of polymers. Generally speaking, in most
cases the internationally adopted combustibility tests set
out by UL94 are performed.
Classification of combustibility behaviour according to
UL94 takes place predominantly in accordance with the following
criteria:
ˌˌUL94-HB (horizontal burning): Material burns and drips.
ˌˌUL94-V2 (vertical burning): Burning period < 30 seconds.
After repeated flaming: Burning period
< 250 seconds, flaming drips are admissible
ˌˌUL94-V1 (vertical burning): Burning period < 30 seconds.
After repeated flaming:
< 250 seconds, flaming drips are not admissible
ˌˌUL94-V0 (vertical burning): Burning period < 10 seconds.
After repeated flaming:
< 50 seconds, flaming drips are not admissible
Combustibility testing to UL94 is generally performed on
raw material. Alongside testing in accordance with the
specifications of UL or using a UL-accredited laboratory,
listing (using so-called yellow cards) is also performed directly
by UL itself. For this reason, a distinction must be
made between materials with a UL listing and materials
which only comply with the requirements of the respective
UL classification (without listing).
Alongside flame retardant classification in accordance with
UL94, a wide range of other industry-specific tests exists
which classify the combustion behaviour of plastics. Depending
on the specific branch of industry, not only combustion
behaviour but under certain circumstances smoke
development, drip behaviour and fume toxicity are also assessed.
Examples of typical additional
flame retardant classification tests
Railway testing standards
ˌˌDIN ISO 5510-2
ˌˌCEN TS 45545-2
ˌˌNFF 16101
Aerospace
ˌˌFAR25-853
Automotive
ˌˌFMVSS 302
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