In the laboratory with no test equipment analysis, it still can be distinguished by density size, combustion phenomenon and color, product performance; after the plastic being colored, it is difficult to judge simply by eye what kind of plastic it is, we can use those methods such as “watch, listen, smell, smash, bite” to comprehensively identify.
Below are some simple methods to identify the commonly used plastics, which refer to their characteristics, product performance, identification, etc.
● Commonly known as the persevering plastic.
● PP is the lightest plastic, with density of 0.9 ~ 0.91g/cm³, lighter than water, it can float on the water surface. PP particles are milky white, translucent, wax-like shape, it burns slowly, the upper end of the flame is yellow, while blue in the middle, with burning drops falling, after extinguishing, there is a smell of paraffin. PP products are light and hard, heat-resistant, corrosion-resistant, with excellent fatigue resistance, good toughness (can withstand tens of thousands of bending & folding). PP products are easy to be aged.
● Note: PP and PE (polyethylene) are similar in characteristics, but the density of PE is 0.91-0.95g/cm³, slightly higher than PP, but less harder，so PP should be carefully distinguished from PE when identifying.
● Commonly known as hard rubber
●Pure PS is a hard, brittle, colorless and transparent plastic, with density of 1.05g/cm³, close to water. Its flame is yellow, flashing, with black smoke. After extinguishing, there is a special smell of coal gas. PS products are hard, brittle, easy to scratch and produce internal stress cracking, which can be broken by hand (brittle damage). PS products have good surface gloss, but low impact strength.
3. Acrylonitrile-styrene copolymer (AS or ASN)
● Commonly known as transparent vigorous adhesive
● SAN (AS) is a slightly blue PS modified transparent granules, with density of 1.08g/m³, slightly heavier than water. SAN burns slowly, the flame is flashing and bright yellow, with black smoke. After extinguishing, there is an irritating odor like PS (fishy smell). SAN products have higher toughness, better than PS products.
● Commonly known as super unbreakable rubber
● ABS is an engineering plastic, the material is ivory yellow (ivory white), opaque plastic, with density of 1.06g/cm³, slightly heavier than water. It burns slowly. Its flame is yellow, flashing, with black smoke, after extinguishing, there is a similar PS irritating fishy smell. ABS glass fiber material is rough, light gray, with poor gloss. High strength, good rigidity, high hardness, impact resistance, good surface gloss are its characters.
● Commonly known as race steel
● The flame is blue when burning, almost colorless (no smoke), after extinguishing there is a strong, irritating formaldehyde odor (easy to tear).POM products are hard, rigid, wear-resistant, with high strength and good surface gloss. There will be a greasy feeling if touch. POM is a very rigid engineering plastic, similar to metals.
● Commonly known as bulletproof rubber
● PC is an excellent comprehensive performance engineering plastics, pure PC density is 1.20g/cm³, heavier than water. PC particles are slightly yellow and transparent. When burning, the frame of PC is bright, with a lot of black smoke, blistering & charring. It can self-extinguish after leaving the fire, with a slightly irritating phenol (fragrance) smell. PC products have high impact strength, good temperature resistance (120 ℃) and good toughness. Internal stress cracking phenomenon often occurs in PC products.
● Commonly known as nylon
● There is a great variety of PA, such as PA6, PA66, PA1010, etc.. The density of Pure PA is between 1.05~1.15g/cm³. PA is a light yellow, translucent material particles, the appearance is rough (not smooth). The flame of PA is yellow up and blue down when burning, with crackling drops into fiber. It can self-extinguish after leaving the fire (no black smoke), there is a burning keratin (nails, hair) smell.
● PVC is a kind of plastic with poor thermal stability, there are several types, which is divided into soft, semi-hard and hard PVC. PVC is generally white powder shape or flakes, or granules, etc. The pure PVC is colorless and transparent material grain, whose density is 1.25~1.45g/cm³, heavier than water. It burns slowly, with yellow and green flame, black smoke. It can self-extinguish after leaving the fire, with an irritating (HCL↑) scorching smell. ｛To check whether the plastic contains chlorine, it is often used to heat the copper wire on the alcohol lamp to a colorless red hot state, and then take a small amount of plastic, place on the copper wire to heat. If the flame appears blue-green (CuCL2), it is believed that the plastic contains chlorine.
● Plexiglass is also known as Acrylic, its material particles are mostly colorless and transparent (some are slightly blue), with a density of around 1.20g/cm³. It is the most transparent products, compared with PS, it is tough and not easy to brittle; but when compared with PC, its toughness and strength are both weaker. The surface hardness is low, easy to be scratched by hard objects.
● PMMA is easy to burn, the flame is blue (yellow top), no smoke, it is easy to occur dripping and bubbling phenomenon when burning; when leaving the fire, it can burn continually, and emit a strong smell of flowers and fruits (similar to the smell of durian) or rotten vegetable odor.
|Specific Gravity Identification Method|
|Test liquid name||Specific Gravity||Test Specific Gravity Apparatus|
|Alcohol for industrial use||0.8||Volumetric Flask|
Test Tube Rack
Stir Bar For Test Tubes
|Sodium chloride (saturated brine)||1.22|