Firing test

The burn test is a quick method for identifying fibers and other materials , especially plastics . It serves to differentiate on the one hand the major types of raw materials and on the other hand between the various synthetic fibers. It is not very suitable for webs made of different fiber materials. To do this, the different fibers would have to be removed from the composite and checked individually. The firing test is a preliminary test. For the exact determination of the raw material, further instrumental methods must be used, such as B. microscopically observed swelling and solution reactions or differential thermal analysis (determination of the glass, crystallization, melting and decomposition temperatures) or IR spectroscopy . Since the preparations or finishes affect the characterization of the fibers, they should be removed, e.g. B. by extracting with dichloromethane or washing.

execution

A snippet, chip or thread of the material to be tested is ignited using a lighter or gas flame. The behavior and appearance of the flame, the smoke / soot, the smell of the combustion exhaust gas and the fire residues are considered. The firing sample is therefore one of the destructive material tests .

The following table gives an overview of the characteristic features of burning plastics or fibers:

Plastic / fiber	flame	Burning smell	Flammability	Burning residue
cotton	bright flame	mild, like burnt paper	burns quickly, continues to glow, embers can be ignited by carefully blowing	slightly whitish, light, finely rubbed ash
Rayon , viscose	like cotton, bright flame	mild, like burnt paper	burns quickly	slightly whitish, light, finely rubbed ash
Wool	yellowish white flame, but quick and little	after burned hair	extremely quickly, especially with loose fibers, the flame goes out easily	blistered, charcoal, crumbly, easily friable ash residue
silk	like wool	like wool, after burned hair	like wool	like wool
Polyethylene (PE)	luminous, bluish inside	like candle wax	flammable	practically no residue, melts, possibly slight traces of soot
Polyacrylonitrile (contained in ABS )	-	after hydrogen cyanide	melting, then burning, development of soot	hard, black melting pearl
Polymethyl methacrylate (PMMA)	burns with a crackling yellowish flame	sweet smell	melting, then burning	dripping and without residue
Polycarbonate (PC)	burns sooty with a glowing flame	phenolic	melting, dripping, goes out after removing the ignition source	dripping and without residue
polyamide	blue flame with a yellowish rim, not sooty	like horn or wool	melting, then burning, foaming and forming brown-black edges	glassy, ​​yellow to dark, stringy melting pearl
polyester	-	indefinitely aromatic	melting, then burning	hard melting bead
Polypropylene	bright	resinous	flammable
Polystyrene (PS)	glowing, sooty	sweetish	flammable	coal-like, easily friable
Polytetrafluoroethylene ("Teflon")	burns up in great heat	stabbing	non-flammable
Polyvinyl chloride (PVC)	greenish flame edge	stabbing; Hydrochloric acid ( HCl ), dioxin and furans are released	difficult to ignite	charred
Polyurethane	bright	stabbing	drips and foams when burning
Phenoplasts	sooting	stinging ( phenol , formaldehyde )	difficult to ignite
Copper fiber	no own flame; colors the flame greenish-blue	no smell	not noticeably flammable; the fibers become red-hot and then pearl together	-
glass fiber	no own flame	no smell	incombustible; the fibers become red-hot and then pearl together	-

Individual evidence

1. ↑ Wolfgang Bobeth (Ed.): Textile fibers. Texture and properties . Springer-Verlag, Berlin / Heidelberg / New York 1993, ISBN 3-540-55697-4 , p. 182 f.
2. ↑ Fabia Denninger, Elke Giese: Textile and Model Lexicon , completely revised and expanded edition, Deutscher Fachverlag GmbH, Frankfurt am Main 2006, vol. A - K, ISBN 3-87150-848-9 , p. 90.
3. ↑ Alfons Hofer: fabrics 1 - raw materials: fibers, yarns and effects . 8th, completely revised and expanded edition, Deutscher Fachverlag, Frankfurt am Main 2000, ISBN 3-87150-671-0 , p. 592.