Common identification methods for plastic products
Plastic identification methods usually use appearance and use, density test, softening point or melting point, combustion test, and comprehensive identification methods. The following are several commonly used methods for everyone to learn:
Appearance and use
To analyze an unknown polymer sample, first look at it with your eyes and touch it, and make a preliminary judgment on which category it belongs to based on its appearance. If possible, you should also understand its source and know as much as possible about its use;
◎Transparency and color
Crystalline → translucent/opaque (PP, PE, Nylon, POM, PET, …)
Amorphous → transparent (PC, PMMA, GPPS, SAN, PPO)
◎Touch and mechanical properties
Pulling, squeezing, knocking or bending the sample by hand can sense the approximate strength and toughness of the material: scratching with fingernails (or with the help of tools such as nails) can determine the hardness of the material. These can be used to preliminarily identify the general type of material.
◎ Use of plastic products
Qualitative identification without background knowledge is very difficult. However, if the source of the sample and other background knowledge of the usage are known, the scope of identification is greatly reduced.
For example: unbreakable plastic liner thermos
Density test
Isodensity method (refer to ASTM D1505; ISO R 1183 method D)
The density of the solid can be measured by suspending the solid to be tested in a liquid of known density (i.e., the density is equal).
Solution Specific gravity Solution Specific gravity
Industrial alcohol 0.8 Sodium chloride 1.22
Water 1 Zinc chloride 1.63
Magnesium chloride 1.33
Combustion test
◎The method of combustion test is very simple. Use tweezers or a scraper to support a small piece of sample and heat it directly with a flame. Generally, let one corner of the sample approach the edge of the flame. For samples that are easy to ignite, you can first distinguish them, and then put them on the flame to burn, and occasionally move them away to determine whether they continue to burn away from the flame.
◎The flammability of materials is related to the elements they contain.
Combustible elements - carbon, chlorine, sulfur and other difficult-to-burn elements - halogens, phosphorus, nitrogen, silicon, boron, etc.
The color of the flame is usually related to the element
Yellow - plastics containing only carbon and hydrogen, such as PS
Blue - plastics containing oxygen, such as POM
Green - plastics containing chlorine, such as PVC
White - plastics that burn fiercely, such as cellulose nitrate, etc.
