Simple identification of plastic types

- Jan 02, 2019-

Identification

Plastics are often sorted before recycling used plastics by various plastic recycling methods. Due to the complexity and complexity of plastic consumption channels, some post-consumer plastics are difficult to distinguish by simple appearance. Therefore, it is best to indicate the variety of materials on plastic products. China has formulated GB/T16288-2008 “Recycling Mark for Plastic Packaging Products” with reference to the material variety label proposed and implemented by the American Plastics Association (SPE). Although the above marking method can be used to facilitate sorting, there are still many unmarked in China. The plastic products bring difficulties to the sorting. In order to separate the different types of plastics for classification and recycling, we must first grasp the knowledge of identifying different plastics. The following describes the simple identification method of plastics:

Appearance identification

By observing the appearance of plastics, it is possible to initially identify a large category of plastic products: thermoplastics, thermosets or elastomers.

Generally thermoplastics are available in both crystalline and amorphous forms. The appearance of the crystalline plastic is translucent, opaque or opaque, and it is transparent only in the state of the film, and the hardness is soft to horny. Amorphous is generally colorless, completely transparent when no additives are added, and hardness is harder than horny rubber (additives such as plasticizers are often added at this time). Thermoset plastics typically contain fillers and are opaque, such as when they are free of fillers. The elastomer has a rubbery feel and a certain stretch ratio.

Simple identification

The first is to look at it, because dark color pigments are generally very toxic, so in general, the darker the color, the more toxic the plastic. Another important reason for dyeing plastics is that the raw materials are waste plastics in order to cover up the original colors.

The second is to smell, as long as the plastic has an odor, no matter how the food can not be loaded, the odor is generally added to the product, such as additives, colorants and other additives or residual monomers.

The third is to touch, the plastic containing food is generally smooth and shiny to touch, if the hand feels not smooth, especially the sticky must not be loaded with food, because there are too many additives, you can not imagine more, may Accounted for more than 50%.

Next, simply say some materials, packaged foods generally use PP (polypropylene), PE (polyethylene), these two are relatively safe, the plastic wrap film in the supermarket is generally PP, and the hot water pipe at home is also PP, because Be sure to be non-toxic. PC (polycarbonate) is usually used for plastic cups that can hold hot water, but the disc is also used, and the waste is returned to the furnace. It is not a problem to use PVC in the down pipe.

Identification method

1. Density method: By examining the density of various plastics and using liquid as a medium to see its ups and downs, it is possible to roughly identify the major categories of plastics. Assuming that the plastic can float in the water, it can be judged that the raw material is not PVC.

2, combustion method: by burning plastic to view the color of the flame and the smell and smoke emitted when burning, usually the polyolefin flames are mostly blue or light blue, the smell is mild and light, the smoke is white, and most of the belt The raw materials of benzene or chlorine are easy to emit black smoke after burning, and the smell is strong, and ABS is. In addition, such as PE, PP has dripping phenomenon, while PVC and so on, there is no drenching, but there is self-extinguishing phenomenon.

3, optical method: by observing the transparency of raw materials for identification, generally commonly used transparent raw materials are: PS, PC, PMMA, AS; translucent raw materials are: PE, random copolymer PP, homopolymer PP, soft PVC, transparent ABS, etc. Other raw materials are basically opaque.

4, color discrimination method: Generally speaking, if the raw material without additives, if it contains double bonds, the color will be slightly yellow, such as ABS, due to the copolymerization of butadiene, the polymer still contains double bonds after polymerization. Therefore, it will be slightly yellow.