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Fire pro­tec­tion for plas­tic and rub­ber products

19.10.2022   | Ste­fanie Schelberg

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Fire pro­tec­tion is an impor­tant issue and, depend­ing on the area of appli­ca­tion, must be tak­en into account in the devel­op­ment of plas­tic and rub­ber com­po­nents. If, for exam­ple, an elec­tron­ic prod­uct or the equip­ment of a vehi­cle catch­es fire, not only mate­r­i­al assets but also human lives are at risk. For this rea­son, the mate­ri­als used must meet fire safe­ty stan­dards to pro­vide the best pos­si­ble pro­tec­tion in the event of a fire.

At Jäger, we encounter two of these stan­dards par­tic­u­lar­ly fre­quent­ly: the Amer­i­can UL94 and the Euro­pean DIN EN 45545.

UL94 — Fire pro­tec­tion for plas­tics in equip­ment and applications

UL94 is a fire pro­tec­tion stan­dard issued by the U.S. orga­ni­za­tion Under­writ­ers Lab­o­ra­to­ries (UL), which spe­cial­izes in prod­uct and mate­r­i­al cer­ti­fi­ca­tions. The stan­dard tests the flam­ma­bil­i­ty of plas­tics used in com­po­nents in elec­tri­cal and house­hold appli­ances and has been har­mo­nized with sev­er­al inter­na­tion­al standards.

Its mea­sure­ment cri­te­ria assess burn­ing rate, extin­guish­ing time, after­glow dura­tion and droplet for­ma­tion, among oth­er things. In total, it includes twelve clas­si­fi­ca­tions, depend­ing on the appli­ca­tion of the mate­r­i­al being tested:

The test method depends on the respec­tive flam­ma­bil­i­ty class. The test spec­i­men is aligned either hor­i­zon­tal­ly (mark­ing H) or ver­ti­cal­ly (mark­ing V) and then exposed to a defined flame of a Bun­sen burn­er for a cer­tain time. The most strin­gent flame retar­dant clas­si­fi­ca­tion is the 5VA test.

Test spec­i­men in the flame of a bun­sen burner

The hor­i­zon­tal HB clas­si­fi­ca­tion tests the rate of fire after a sin­gle flame expo­sure, tak­ing into account the thick­ness of the mate­r­i­al. The ver­ti­cal flam­ma­bil­i­ty clas­si­fi­ca­tions V‑2 to V‑0 flame test twice. They test burn­ing and after­glow dura­tion and test whether burn­ing par­ti­cles detach from the mate­r­i­al sam­ple, ignit­ing a cot­ton indi­ca­tor locat­ed under the test specimen.

Class­es 5VB and 5VA have more strin­gent cri­te­ria. Here, the test spec­i­men is exposed five times to a flame that is approx­i­mate­ly ten times stronger than in the tests accord­ing to V‑0, V‑1, V‑2 and HB. Both the burn­ing behav­ior of ver­ti­cal­ly aligned bars and the hole for­ma­tion on hor­i­zon­tal­ly clamped plates are tested.

The VTM cri­te­ria are sim­i­lar to those for class­es V‑2 through V‑0, but the flame is applied for only 3 sec­onds instead of 10. For HBF tests, the flame appli­ca­tion time is sig­nif­i­cant­ly longer at 60 seconds.


You can read the exact test cri­te­ria for the indi­vid­ual flam­ma­bil­i­ty class­es on the Under­writ­ers Lab­o­ra­to­ries web­site.

DIN EN 45545 — Fire pro­tec­tion in rail vehicles

DIN EN 45545 is a Euro­pean stan­dard and focus­es on fire pro­tec­tion in rail vehi­cles. It is divid­ed into two parts: 

The stan­dard is intend­ed to ensure that pas­sen­gers and train crews suf­fer as lit­tle dam­age to their health as pos­si­ble in the event of a fire and can be evac­u­at­ed smooth­ly. Mate­r­i­al assets (e.g. the vehi­cle itself) play a sub­or­di­nate role.

The design of the fire pro­tec­tion reg­u­la­tions in DIN EN 45545–2 depends on the haz­ard lev­el. This is made up of the design class and the oper­at­ing class, which are described in DIN EN 45545–1.

The design class cat­e­go­rizes the con­struc­tion of the vehi­cle as well as its pri­ma­ry function:

The oper­at­ing class reflects the con­di­tions of use of the vehi­cle and thus the con­text of its operation:

The haz­ard lev­el is derived from a matrix whose dimen­sions rep­re­sent con­struc­tion type and oper­at­ing class. There are three cat­e­gories: HL1 (low haz­ard), HL2 (medi­um haz­ard) and HL3 (high hazard).


The clas­si­fi­ca­tion shows that the require­ments increase the more crit­i­cal the evac­u­a­tion situation.

The test pro­ce­dures and lim­it val­ues pro­vid­ed for indi­vid­ual com­po­nents depend on the haz­ard lev­el and are described in detail in DIN EN 45545–2. The require­ments dif­fer, among oth­er things, with regard to smoke devel­op­ment, oxy­gen con­tent and the gen­er­a­tion of tox­ic gases.

If you are inter­est­ed, you can pur­chase the com­plete stan­dard here.

Con­se­quences for mate­r­i­al selection

The pre­sump­tion is that the mate­r­i­al with the high­est fire pro­tec­tion class is always the best choice. How­ev­er, max­i­miz­ing the fire rat­ing may mean that the mate­r­i­al los­es oth­er desir­able prop­er­ties. Mate­r­i­al selec­tion in rub­ber and plas­tics is com­plex. There are sev­er­al fac­tors to con­sid­er in rela­tion. Turn­ing one screw can have con­se­quences elsewhere.

For exam­ple, the use of addi­tives that improve flame retar­dan­cy can have a neg­a­tive impact on oth­er prop­er­ties, such as UV sta­bil­i­ty, flex­ur­al strength or tem­per­a­ture sta­bil­i­ty of the mate­r­i­al. In addi­tion, increased require­ments for mate­ri­als are often also asso­ci­at­ed with increased mate­r­i­al costs and the choice of mate­ri­als is nar­rowed down.

It there­fore makes sense to coor­di­nate the actu­al min­i­mum require­ments based on the appli­ca­tion sit­u­a­tion along the sup­ply chain. Thus, in case of doubt, the use of an overqual­i­fied mate­r­i­al, and thus high­er mate­r­i­al costs, can be avoid­ed and a pos­si­ble com­pet­i­tive dis­ad­van­tage can be ruled out.


Secure the Start of Production 

Learn which fac­tors influ­ence your SOP!

Autorin: Ste­fanie Schelberg

Ste­fanie Schel­berg is a trained indus­tri­al clerk and busi­ness admin­is­tra­tor. She has been work­ing in sales at Jäger since 2016 and is respon­si­ble for cus­tomer-spe­cif­ic products.

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