Recycled plastics refer to plastic raw materials obtained by processing waste plastics through physical or chemical methods such as pretreatment, melt granulation, and modification. It is the reuse of plastics.
◆Uses of recycled plastics
Plastics have good processing properties and are easy to shape, such as: blowing, extrusion, pressing, easy to cut, and easy to weld. In production and life, there are many plastics that can be granulated, such as waste food bags, sandals, wires, wire boards, agricultural films, pipes, barrels, basins, strapping tapes and various waste plastic products. They can be repeatedly molded and processed to produce plastic raw materials, and then through special processes and formulas, they can be used to make machine parts and components; they can be used to make water pipes, agricultural machinery, packaging bags, cement bags; they can replace some wooden products; they can be used to make various plastic bags, barrels, basins, toys and other plastic products and daily necessities.
◆Advantages of recycled plastics
World resources are always a hot topic for mankind. The slogan of saving resources has gradually penetrated into people's hearts. Therefore, the awakening of recycled materials is inevitable. In this way, people can truly achieve environmental protection and energy saving through the recycling of resources. Recycled materials are processed according to different needs, and the corresponding products are manufactured, so that resources will not be lost.
◆Performance changes
PVC: The color change is more obvious after regeneration. After one regeneration extrusion, it will be light brown, and after three regenerations, it will almost become opaque brown. The specific viscosity remains unchanged in the second time, and there is a tendency to decrease after more than two times. Whether it is hard or soft PVC, stabilizers should be added during regeneration. In order to make the re-product glossy, ABS 1%-3% for mixing can be added during regeneration.
PE: After PE is recycled, its performance is reduced and its color turns yellow. After multiple extrusions, the viscosity of high-density polyethylene decreases, while the viscosity of low-density polyethylene increases.
PP: After one regeneration, the color remains almost unchanged and the melt index increases. After more than two regenerations, the color becomes heavier and the melt index still increases. After regeneration, the breaking strength and elongation decrease, but there is no problem in use.
PS: The color turns yellow after regeneration, so the regenerated PS is generally color-differentiated. The degree of decline in the performance of the recycled material is proportional to the number of regenerations. The breaking strength does not change significantly when the addition amount is less than 60%, and the limiting viscosity does not change significantly when the addition amount is less than 40%.
ABS: The color change after regeneration is more obvious, but when the use amount does not exceed 20-30%, the performance does not change significantly.
PA: Nylon recycling also has the problem of discoloration and performance degradation, and the amount of mixing should be less than 20%. The recycled elongation decreases, but the elasticity tends to increase.
◆How to distinguish the quality of recycled plastics
1. Look at the color
The lighter the color (even colorless and transparent), the wider the scope of use and the higher the grade. For example, white can be adjusted to a variety of other colors, or it can be made back to white products, and the price is also high. Secondly, due to the needs of the product, various ingredients are added to the raw materials.
2. Look at the CaC03 (stone powder) content
The more CaC03 content, the lower the grade, and the lower the price. From the naked eye, if the product is not bright and has no luster (except matte), the CaC03 content is high, and it will feel heavy. If it is burned with fire, the burned part will turn red and turn into ash after being extinguished. In addition, we must pay attention to the reinforced (referring to glass fiber) products. The only reinforced products that can be used are PA, PBT, PP, etc., and the prices are not high. There are also several alloy materials. At present, only ABS+PC is sold in China, and the others are not available. Then judge whether the mixed materials can be reused according to the specific gravity (density) of the raw materials. At present, the most problematic ones are ABS and PS mixed, PC and PMMA mixed, PVC flakes (bottle materials) and PEl, flakes mixed, PE and PP mixed half and half. After these materials are mixed, they are difficult to use because of their similar density.
3. See whether the recycled plastic material is pure
The purer the material, the higher the grade; if the material is impure, the grade is low, and some mixed materials are even not wanted by anyone.
4. Difference from waste plastics
Waste plastics are plastic products that are directly crushed into powder or granules, and it is still possible to distinguish what kind of material it is, such as injection molding, wire drawing, or film, etc. Recycled plastics are recycled so many times that it is impossible to accurately distinguish what they are. They can only be graded according to the number of cycles, starting with the least, and are divided into special grade, first grade, and second grade.
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