Appearance method:
Appearance identification mainly observes the appearance characteristics of plastic products through vision, touch, smell, etc., such as the shape, transparency, color, gloss, hardness, etc. of the product.
After plastics are recycled and reprocessed, the color, gloss, strength, etc. will change. The color of plastics without recycled materials will generally be more transparent, and products mixed with recycled materials will reduce the transparency; the gloss of recycled materials is relatively poor; experienced injection molding Personnel can preliminarily determine the strength of the plastic by biting it with teeth. Plastics with added recycled materials are more brittle. The appearance method is generally used as a preliminary identification of plastic recycled materials.
Physical property testing method:
Different types of plastics usually have relatively large differences in density, and the density of the same plastic before and after recycling will also vary greatly.
The density method can be used to roughly identify plastic regrind, but it cannot be used to completely judge plastic regrind because many voids or other defects will be produced during the plastic recycling and reproduction process. For example, the regeneration process of ABS/PC will produce many tiny holes, and the number of holes increases with the number of regenerations.
Strength properties such as impact strength, tensile strength, compressive strength, and flexural strength will change with the increase in plastic recycling content, and there will be a significant decrease trend, especially the tensile strength and flexural strength.
The reduction in these strength properties is closely related to the formation of voids and defects and the reduction in molecular weight of the recycled materials during the recycling process. Therefore, for the identification of plastic recycled materials, these strength properties of plastics can be tested, and through comparison, it can be initially determined whether the product contains recycled materials.
Dissolution method:
The solubility of plastics in different organic solvents can be used to identify different plastics, and also to identify plastic recycling. Since it is difficult to achieve higher purity during the recycling and reuse process of recycled materials, there will be some impurities, resulting in poor solubility of the recycled materials. If the raw materials are good, there will be residues in the plastic recycling process during the dissolution process of organic solvents.
Commonly used organic solvents for dissolving plastics include benzene, xylene, tetrahydrofuran, ether, acetone and formic acid. However, the dissolution method has very large limitations. Many plastic products are added with various fillers during processing, which affects the comparison between recycled materials and original materials.
Therefore, the dissolution method has a large error in identifying the recycled materials, but it is a relatively fast method to identify the type of plastic recycled materials.