How is waste plastic reprocessed? Is it impossible to reach food grade after reprocessing?
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- Unsolveddestoon
- 2021-07-12 23:07
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- 1Flooranonymity
- 2021-08-05 21:02
There are also many types of reprocessing. At present, there are three types of waste plastics:
1 Landfill
It is easy to permanently damage the soil, but the cost is low. Many countries had abolished it.
2 Incineration
Many things are classified as hazardous waste after incineration. This has only emerged in the last two years.
Therefore, the incineration chimney needs to be equipped with additional filtering devices, so the cost is higher.
3 Granulation
Divided into physical and chemical methods
Most of the physical methods are low cost and the process is easy to understand.
It must be crushed, sorted, washed first, and the washing is divided into hot washing and cold washing. Melt, cool and granulate.
It is generally can not reach not food grade.
1. Even if the recycled materials are carefully sorted, separated and cleaned, inhomogeneity and residual impurities still exist. During the processing of new materials and the first life cycle, irreversible changes in the molecular chain have already occurred, including changes caused by mechanochemistry, chemistry, and radiation. Disproportionation and depolymerization reactions lead to low molecular weight products. Polycondensates such as polyamides and polyesters are hydrolyzed to reduce their molecular weight.
2.The recycled material also contains impurities. These impurities are either formed by the conversion product in a small concentration, or formed by foreign impurities, and they cannot be removed by purification methods.
3.When we produce plastic products, we add some materials to improve the performance of plastics or some materials used in the post-processing process. These materials may be inorganic or organic, such as flame retardants, printing inks, paint residues, surfactants and contact Residues of the medium. These substances are often harmful to polymers because they are thermally unstable, degradation products reduce material properties and reduce the stability of recycled materials.
In the last two points, toxic and harmful substances may be produced during reproduction.
1 Landfill
It is easy to permanently damage the soil, but the cost is low. Many countries had abolished it.
2 Incineration
Many things are classified as hazardous waste after incineration. This has only emerged in the last two years.
Therefore, the incineration chimney needs to be equipped with additional filtering devices, so the cost is higher.
3 Granulation
Divided into physical and chemical methods
Most of the physical methods are low cost and the process is easy to understand.
It must be crushed, sorted, washed first, and the washing is divided into hot washing and cold washing. Melt, cool and granulate.
It is generally can not reach not food grade.
1. Even if the recycled materials are carefully sorted, separated and cleaned, inhomogeneity and residual impurities still exist. During the processing of new materials and the first life cycle, irreversible changes in the molecular chain have already occurred, including changes caused by mechanochemistry, chemistry, and radiation. Disproportionation and depolymerization reactions lead to low molecular weight products. Polycondensates such as polyamides and polyesters are hydrolyzed to reduce their molecular weight.
2.The recycled material also contains impurities. These impurities are either formed by the conversion product in a small concentration, or formed by foreign impurities, and they cannot be removed by purification methods.
3.When we produce plastic products, we add some materials to improve the performance of plastics or some materials used in the post-processing process. These materials may be inorganic or organic, such as flame retardants, printing inks, paint residues, surfactants and contact Residues of the medium. These substances are often harmful to polymers because they are thermally unstable, degradation products reduce material properties and reduce the stability of recycled materials.
In the last two points, toxic and harmful substances may be produced during reproduction.