Routine identification methods for PVC

Identification by combustion method
Softening or melting temperature range: 75~90 ° C;
Combustion: self extinguishing after ignition;
Combustion flame state: yellow at the top and green at the bottom with smoke; After fire: off fire; Odor: Irritating sour taste.
This method is the most simple and direct, and is generally preferred.
Identification of solvent treatment
Solvent: tetrahydrofuran, cyclohexanone, dimethylformamide;
Non solvent: methanol, acetone, heptane.
Add the suspected PVC plastic to the above solvents and observe the dissolution of the plastic to determine whether it is PVC. After the solvent is heated, the dissolution effect will be more obvious.
Hydrometric method
The specific gravity of PVC is 1.35~1.45, generally about 1.38. Polyvinyl chloride and other plastics can be distinguished by specific gravity difference or by measuring specific gravity. However, because PVC can change its specific gravity and hardness greatly by adding plasticizers, modifiers and fillers, and many properties of PVC plastic will change due to the addition of some components, leading to the ineffectiveness of our common identification methods and even the change of phenomena, making it impossible to make accurate judgments. For example, the density of plasticized polyvinyl chloride (about 40% plasticizer) is 1.19~1.35; However, PVC hard products are increased to 1.38~1.50. In case of high filled PVC products, the density sometimes exceeds 2.
In addition, it can also be determined by determining whether there is chlorine in the material, but because vinyl chloride copolymer, neoprene rubber, polyvinylidene chloride, chlorinated polyvinyl chloride, etc. all contain a high proportion of chlorine, they must be identified by pyridine color reaction. Note that before the test, the test sample must be extracted with ether to remove the plasticizer. Test method: dissolve the sample taken with ether benzene in tetrahydrofuran, filter out the insoluble components, add methanol to precipitate them, and dry them below the first 75 degrees after extraction. A small amount of dried sample does not need 1mL pyridine to react with it. After a few minutes, add 2 drops of methanol solution of 5% sodium hydroxide (1g sodium hydroxide is dissolved in 20mL methanol) to the site. Observe the color immediately, and observe again after 5min and 1h. Different chlorinated plastics can be identified according to their colors.