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How to Identify 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 500°F/260°C, the material 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 odor, a known sample is most helpful for comparison.) Finally, check your observations against the known characteristics of each plastic given on page 93. 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
Yes
Slow
-
  Type 6/6
-
Burnt wool
or hair
Blue,
yellow tip
Yes
-
-
-
Slow
More rigid than
Type 6 nulon
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 phenol
c
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


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