Using The Burn Test to Identify Plastic Materials

Here is a simplified guide that will help you to identify many common types of plastic materials using a flame source such as a cigarette lighter, torch, or bottled gas burner. Naturally, the burn test should be used only for tentative identification. Many complex plastic compounds require a rigorous spectral or destructive chemical analysis for a positive identification.

To initially determine whether a material is thermoplastic (meltable) or thermoset (non-meltable) type, heat a metal or glass stirring rod until it glows red or orange (to about 500°F / 260°C) and press it against the sample. If the sample softens, the material is a thermoplastic; if it does not, it's probably a thermoset.

Next, hold the sample to the edge of a flame until it ignites. If no flame is produced quickly, hold the sample in the flame for about 10 seconds. If the material burns, note the color of the flame, the nature of the smoke, the presence of soot in the air and whether, while burning, the sample drips.

Next, extinguish the flame and cautiously smell the fumes. To identify the odor, samples of known plastic samples for comparison can be most helpful. Finally, check your observations against the known characteristics of each plastic as shown in the table below. Once you have made a tentative identification, it is usually desirable to repeat the flame test once or twice to confirm the results of the original identification. Remember that additives may affect results. For example: flame retardants can mask the polymer material's normal flame & smoke burning characteristics.

PLASTIC MATERIAL BURN TEST CHARACTERISTICS
Materials	No Flame	Burns, but Extinguishes on Removal of Flame Source			Continues to Burn after removal of Flame Source				Remarks
	Odor	Odor	Color of Flame	Drips	Odor	Color of Flame	Drips	Speed of Burning
THERMOPLASTICS
ABS		Acrid	Yellow, blue edges	No	Acrid	Yellow, blue edges	Yes	Slow	Black smoke with soot in air
Acetals	-	-	-	-	Formaldehyde	Blue, no smoke	Yes	Slow
Acrylics	-	-	-	-	Fruity	Blue, yellow tip	No (cast) Yes (molded)	Slow	Flame may spurt if rubber modified
Cellulosics
Acetate	-	Vinegar	Yellow with sparks	No	Vinegar	Yellow	Yes	Slow	Flame may spark
Acetate Butyrate	-	-	-	-	Rancid butter	Blue, yellow tip	Yes	Slow	Flame may spark
Ethyl Cellulose	-	-	-	-	Burnt sugar	Yellow, blue edges	Yes	Rapid	-
Nitrate	-	-	-	-	camphor	White	No	Rapid	-
Propionate	-	-	-	-	Burnt sugar	Blue, yellow tip	Yes	Rapid	-
Chlorinated Polyether	-		Green, yellow tip	No	-	-	-	-	Black smoke with soot in air
Fluorocarbons
FEP	Faint odor of burnt hair	-	-	-	-	-	-	-	Deforms; no combustion, but drips
PTFE	Faint odor of burnt hair	-	-	-	-	-	-	-	Deforms; does not drip
CTFE	faint odor of acetic acid	-	-	-	-	-	-	-	Deforms; no combustion, but drips
PVDF	acidic	-	-	-	-	-	-	-	Deforms
Nylons
Type 6	-	-	-	-	Burnt wool	Blue, yellow tip	Yes	Slow	-
Type 6/6	-	Burnt wool or hair	Blue, yellow tip	Yes	-	-	-	Slow	More rigid than Type 6 nylon
Phenoxies	-	Acridd	Yellowc	Noc	Acridd	Yellowd	Yesd	Slowd	Black smoke with soot in air
Polycarbonates	-	Faint, sweet aromatic ester	Orange	Yes	-	-	-	-	Black smoke with soot in air
Polyethylenes	-	-	-	-	Paraffin	Blue, yellow tip	Yes	Slow	Floats in water
Polyphenylene
Oxides (PPO)	-	Phenol	Yellow-orange	No	-	-	-	-	Flame spurts; very difficult to ignite
Modified Grade	-	Phenol	Yellow-orange	No	-	-	-	-	flame spurts; difficult to ignite, soot in air
Polyimides	b	-	-	-	-	-	-	-	Chars; material very rigid
Polypropylenes	-	Acrida	Yellowa	Yellowa	Sweet	Blue, yellow tip	Yes	Slow	Floats in water; more difficult to scratch than polyethylene
Polystyrenes	-	-	-	-	Illuminating Gas	Yellow	Yes	Rapid	Dense black smoke with soot in air
Polysulfones	-	b	Orange	Orange	-	-	-	-	Black smoke
Polyurethanes	-	-	-	-	b	Yellow	No	Slow	Black smoke
Vinyls   Flexible	-	Hydrochloric acid	Yellow with green spurts	No	-	-	-	-	Chars, melts
Rigid	-	Hydrochloric acid	Yellow with green spurts	No	-	-	-	-	Chars, melts
Polyblends
ABS/Polycarbonate	-	-	-	-	b	Yellow, blue edges	No	-	Black smoke with soot in air
ABS/PVC	-	Acrid	Yellow, blue edges	No	-	-	-	-	Black smoke with soot in air
PVC/Acrylic	-	Fruity	Blue, yellow tip	No	-	-	-	-
THERMOSETS
Alkyds	-	-	-	-	-	-	-	-	-
Diallyl Phthalates	-	-	-	-	Phenolic	Yellow	No	Slow	Black smoke, cracks
Diglycol Carbonate	-	-	-	-	Acrid	Yellow	No	Slow	Black smoke with soot
Epoxies	-	-	-	-	Phenol	Black smoke	No	Slow	Black smoke with soot in air
Melamines	Formaldehyde and fish		-	-	-	-	-	-	-
Phenolics	Formaldehyde and phenolc	Phenol and wood or paperd	Yellowd	No	-	-	-	-	May crack
Polyesters	-	Hydrochloric acida	Yellowa	Noa	b	Yellow, blue edges	No	Slow	Cracks and breaks
Silicones	b	-	-	-	-	-	-	-	Deforms
Ureas	Formaldehyde	-	-	-	-	-	-	-	-

a Flame retardant   b Nondescript   c Inorganic filler   d Organic filler

Ref: Materials Engineering, Penton/IPC, Cleveland, Ohio