IDENTIFYING PLASTICS

Here is a preliminary guide that will help you to identify many of the basic types of plastics using simple techniques and readily available tools. Naturally, these tests should be used only for tentative identification because some complex plastic compounds require a rigorous analysis for identification.

To initially determine whether a material is thermoset or thermoplastic, heat a stirring rod (to about 260°C). If the material softens it is a thermoplastic; if not, it is probably a thermoset.

Next, hold the sample to the edge of a flame until it ignites. (Hold in the flame for about 10 seconds if no flame is produced immediately). If the material burns, note the nature of the smoke, the presence of soot in the air and, if while burning, the sample drips. Next, extinguish the flame and cautiously smell the fumes. (In identifying the odour, a known sample is most helpful for comparison). Finally, check your observations against the known characteristics of each plastic given below. Once you have made a tentative identification, it is usually desirable to make one additional test to confirm the results of the original identification. Remember additives may affect results; for example, flame retardants would mask the polymer's normal burning characteristics.

Materials No Flame Odour Burns, but extinguishesColour of flameDripsContinues to burn
after removal of flame source odour
Colour of flameDripsSpeed of burningRemarks
THERMOPLASTICS
ABSAcridYellow,
blue edges
NoAcridYellow,
blue edges
YesSlowBlack smoke
with soot in air
ACETALSFormaldehydeBlue,
no smoke
YesSlow
ACRYLICSFruityBlue,
yellow tip
No (cast)
Yes (molded)
SlowFlame may spurt
if rubber modified
CELLULOSICS
ACETATEVinegarYellow
with sparks
NoVinegarYellowYesSlowFlame may spark
ACETATE BUTYRATERancid butterBlue,
yellow tip
YesSlowFlame may spark
ETHYL CELLULOSEBurnt sugarYellow,
blue edges
YesRapid
NITRATECamphorWhiteNoRapid
PROPIONATEBurnt sugarBlue,
yellow tip
YesRapid
CHLORINATED POLYETHERGreen,
yellow tip
NoBlack smoke
with soot in air
FLUOROCARBONS
FEPFaint odour
burnt hair
Deforms;
no combustion,
but drips
PRTFEFaint odour
burnt hair
Deforms;
does not
drip
CTFEFaint odour
acetic acid
Deforms;
no combustion,
but drips
PVFAcidicDeforms
NYLONS
TYPE 6Burnt woolBlue,
yellow tip
Slow
TYPE 6/6Burnt wool
or hair
Blue,
yellow tip
YesSlowMore rigid than Type 6 nylon
PHENOXIESAcidicYellowNoAcridYellowYesSlowBlack smoke
with soot in air
POLYCARBONATESFaint, sweet
aromatic ester
OrangeYesAcridYellowYesSlowBlack smoke
with soot in air
POLYETHYLENESParaffinBlue,
yellow tip
YesSlowFloats in water
OXIDES (PPO)PhenolYellow-orangeNoYel<br>lowYesSlowFlame spurts;
very difficult to ignite
MODIFIED GRADEPhenolYellow-orangeNoYellowYesSlowFlame spurts;
difficult to ignite
soot in air
POLYIMIDESChars;
material very rigid
POLYPROPYLENESAcridYellowYellowSweetBlue,
yellow tip
YesSlowFloats in water; more difficult to scratch than polyethylene
POLYSTYRENESIlluminating GasYellowYesRapidDense black smoke with soot in air
POLYSULFONESOrangeOrangeBlack smoke
POLYURETHANESYellowNoSlowBlack smoke
POLYBLENDS
ABS/POLYCARBONATEYellowNoBlack smoke
ABS/PVCAcridYellow, blue edgesNoBlack smoke with soot in air
PVC/ACRYLICFruityBlue, yellow tipNo
THERMOSETS
ALKYDS
EPOXIESPhenolBlack smokeNoSlowBlack smoke with soot in air
MELAMINESFormaldehyde and phenoicPhenol & wood or paperedYellowNoMay crack
POLYESTERSYellowNoYellow, blue edgesNoSlowCracks and breaks