How do you identify the material of plastic parts?
Due to the limitation of factory conditions, unlike laboratories, which can be analyzed by instruments, they can only be identified by appearance. Preliminary judgment of different plastics by combustion method requires certain experience and long-term contact. However, there are limitations. If a part is made of several materials, it will increase the difficulty of appearance identification. It is also difficult to distinguish the plastics from various combustion characteristics and odors by combustion method.
The identification methods of several commonly used materials are introduced below.
I. Appearance Recognition Method
(1) PE, PP and PA have different flexibility. They have hard wax-like greasy touch and soft horny sound when they are knocked. Compared with PS, ABS, PC, PMMA, etc., there is no extensibility, the hand has a sense of rigidity, and the sound is clear when tapping.
(2) The relative density of PE and PP is less than 1, so they float in water; most other plastics are more than 1, so they sink in water.
(3) Before dyeing, LDPE plastic granules are opaque, transparent, soft and flexible, slightly elongated, and easily bitten and deformed with teeth. HDPE is milky white, opaque, slightly hard texture, not late extension, deformable with teeth breathing. PP is white, translucent, lighter and more rigid than PE. It is extremely difficult to deform with teeth.
(4) The difference between PS, HIPS and ABS is mainly PS brittleness, while HIPS and ABS are toughness, so PS is brittle when bending. The latter two are hard to break and whiten in the bend. It is easy to identify before dyeing; PS is transparent, HIPS is milky white, ABS is light ivory.
2. Combustion Observation Method
Different materials have different combustion behavior when burning, such as flame color and odor (plastic degraded due to heat in the actual processing process will also have a low molecular weight special taste), which is also the basic method of identifying common materials.
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Flame color produces smoke and melting odor.
PE Flammable Continuous Combustion Yellow and Blue Few Drops of Paraffin Flavor
PP Flammable Continuous Combustion with Yellow, Blue and Less Oil Flavor
PS Flammable Continuous Flammable, Yellow, Blue, Smokey and Foaming Styrene Flavor
Flammable and Continuous Combustion of ABS Fume Coking Rubber Flavor
HIPS Flammable Continuous Flammable Full Yellow Smoke Foaming Rubber without Dropping
Under PMMA slow-burning and continuous-burning, light blue and top white all bubbles, blossoms and fruits stink.
PA Flammable Continuous Burning with Fewer Drops of Burning Hair
POM can continue to burn non-dripping pungent taste
PET Flammable Continuous Combustion with Fewer Vinegar Flavor
PC slow-burning and non-continuous burning yellow and black soot carbon bundles blistering flower and fruit odor
PVC Flame-retardant Self-extinguishing, Upper Yellow, Lower Green, White Smoke, White Smoke and Spicy Taste
