Changzhou Huisheng Maoxin Plastic Products Co., Ltd.

The identification of plastics can be done by scientific methods such as infrared spectroscopy, paramagnetic resonance and X-ray, but it can also be done by simple methods. Simple identification methods are briefly introduced as follows:

Sensory identification

Sensory identification (organize students to participate in the identification of plastics)

（1） Look

First, look at the color and transparency of the products.

Transparent products include polystyrene and plexiglass.

Translucent products include low-density polyethylene, cellulose plastics, polyvinyl chloride, polypropylene, epoxy resin and unsaturated resin.

Opaque products include high-density polyethylene, polyurethane and various colored plastics.

（2） Listen

When striking with hard objects, the sound is different, polystyrene sounds like metal, and plexiglass sounds thick and stuffy.

（3） Touch

It must be polyolefin if the product feels like wax by hand. Secondly, the degree of hardness and softness can be simply expressed as follows:

Hard → Soft

Polystyrene → Polypropylene → Polyamide → Organic glass → High density polyethylene → Rigid polyvinyl chloride → Low density polyethylene → Soft polyvinyl chloride

Then test the surface hardness and mark the surface with pencils of different hardness to make a difference:

The HB pencil for polyethylene plastic can scratch lines;

Polypropylene plastic with ZH pencil can scratch lines.

Due to the difference of people's physiological conditions, the sensory identification results are different, so this method is only for reference.

Identification basis of several easily mixed plastics

（1） Identification basis of polyethylene and polypropylene plastics

Both polyethylene and polypropylene plastics are opalescent translucent bodies, light in weight and able to float on the water surface, and the combustion phenomenon is basically the same. However, there are also obvious differences between the two: polyethylene has a waxy and smooth feel when touching, and the texture is soft and flexible, while polypropylene has a smooth and delicate feel, but no waxy and smooth feel, and the texture is very hard and flexible; Polyethylene plastic softens significantly in boiling water, while polypropylene plastic does not soften significantly in boiling water; When the polyethylene plastic strip is stretched, "thin neck" is produced, while polypropylene is not.

（2） Identification basis of PVC and polyethylene plastic film

The processing methods of PVC and polyethylene are different: PVC is rolled into a single film, while polyethylene is blown into a cylindrical double-layer bag; From the perspective of color and transparency: polyethylene is milky white and translucent, with a bright surface and a waxy and greasy feel when touched. Multiple layers stacked together are still milky white and translucent, while the transparency of polyvinyl chloride is higher than that of polyethylene, with yellowish color. Multiple layers stacked together are yellowish, with a smooth but sticky feel. Carefully observe the mold fine lines; Different combustion phenomena: polyethylene is flammable, molten and dripping, with paraffin smell, while polyvinyl chloride is nonflammable, with green flame root, and the irritating smell of hydrochloric acid is emitted; Polyethylene can float on the water with small specific gravity, while PVC can sink in the water.

（3） Identification basis of phenolic and urea formaldehyde plastics

Both are thermosetting plastics, which are hard and opaque. They are mainly different in the following aspects: phenolic plastics are generally black brown, while urea formaldehyde plastics are mostly light colored and bright colored; The section structure of phenolic plastic is loose, while that of urea formaldehyde plastic is tight; During combustion, phenol formaldehyde emits phenol odor, carbonization cracking occurs at the part contacting the flame, urea formaldehyde escapes with urea odor, and whitening cracking occurs at the part contacting the flame.

（4） Identification basis of polystyrene, polyvinyl chloride and polyethylene plastics

The identification basis of the three plastics is as follows:

1. Color and transparency

Polystyrene plastic is bright in color and transparent as glass; The color and transparency of PVC plastic are worse than that of polystyrene; Polyethylene plastic translucent body, the appearance is like wax products, and the dye is easy to seep out.

2. Hand feel

Polystyrene has smooth hand feel, hard surface, and is afraid of bumping and extrusion; The handle of PVC is smooth, and the film products are sticky; There are soft and hard products; The handle of polyethylene is waxy and slippery, and the products are soft and resistant to bending.

3. Relative density

The relative density of polystyrene is 1.05~0.06, and it sinks slowly in water; The relative density of PVC soft plastic is 1.24~1.45, and that of rigid plastic is 1.35~1.45, so it sinks rapidly in water; The relative density of high-density polyethylene is 0.94~0.97, and the relative density of low-density polyethylene is 0.91~0.93, so it floats in water.

4. Sound

When hard objects are knocked, polystyrene has a clear metallic sound, PVC is loud but not brittle, and polyethylene is stuffy but not brittle.

5. Flammability

Polystyrene is flammable, the flame is orange, emits flocculent black smoke, and has a pungent smell of styrene monomer; Polyvinyl chloride cannot self ignite, it is extinguished when it is away from the fire, the flame is yellow, the root is green, and the smell of hydrochloric acid is emitted; Polyethylene is flammable, the flame is yellow, the root is blue, and it emits a small amount of black smoke. It softens when burning, drops wax tears like a candle, and emits a paraffin smell.