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Identifying Plastics
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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 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
PRTFE Faint odor of
burnt hair
- - - - - - - Deforms;
does not drip
CTFE faint odor of
acetic acid
- - - - - - - Deforms;
no combustion,
but drips
PVF acidic - - - - - - - Deforms
Nylons                  
Type 6 - - - - Burnt wool Blue,
yellow tip
- 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 - Yellow No Slow b - - - 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 - - - - - - - - -
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 acid>a Yellowa Noa b Yellow,
blue edges
No Slow Cracks and breaks