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 extinguishes | Colour of flame | Drips | Continues to burn after removal of flame source odour | Colour of flame | Drips | Speed of burning | Remarks |
---|---|---|---|---|---|---|---|---|---|
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 odour burnt hair | Deforms; no combustion, but drips | |||||||
PRTFE | Faint odour burnt hair | Deforms; does not drip | |||||||
CTFE | Faint odour 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 | Acidic | Yellow | No | Acrid | Yellow | Yes | Slow | Black smoke with soot in air | |
POLYCARBONATES | Faint, sweet aromatic ester | Orange | Yes | Acrid | Yellow | Yes | Slow | Black smoke with soot in air | |
POLYETHYLENES | Paraffin | Blue, yellow tip | Yes | Slow | Floats in water | ||||
OXIDES (PPO) | Phenol | Yellow-orange | No | Yel<br>low | Yes | Slow | Flame spurts; very difficult to ignite | ||
MODIFIED GRADE | Phenol | Yellow-orange | No | Yellow | Yes | Slow | Flame spurts; difficult to ignite soot in air | ||
POLYIMIDES | Chars; material very rigid | ||||||||
POLYPROPYLENES | Acrid | Yellow | Yellow | 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 | Orange | Orange | Black smoke | ||||||
POLYURETHANES | Yellow | No | Slow | Black smoke | |||||
POLYBLENDS | |||||||||
ABS/POLYCARBONATE | Yellow | No | Black smoke | ||||||
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 phenoic | Phenol & wood or papered | Yellow | No | May crack | ||||
POLYESTERS | Yellow | No | Yellow, blue edges | No | Slow | Cracks and breaks |