The separation of plastics during recycling is a vital process to ensure the reuse of materials. Polymers are separated according to the type of plastic and their quality. This is because different plastic polymers have different characteristics, and mixing them would alter their properties.

Plastic Separation and Recycling

The separation process can vary by region and available resources, but in general, the steps for separation and sorting are as follows.

Plastic Type Identification

Materials are separated into different categories based on their chemical composition. The most common types of plastics are:

Polyethylene Terephthalate (PET)
High-Density Polyethylene (HDPE)
Polyvinyl Chloride (PVC)
Low-Density Polyethylene (LDPE)
Polypropylene (PP)
Polystyrene (PS)
Others

Color Sorting

Plastics such as PET and HDPE are sorted by color. This step is extremely important because transparent and light-colored plastics are more valuable in the recycling market, as they are easier to recycle and can be reused in a wide variety of products.

Size Separation

Because the properties of polymers (strength, flexibility, or resilience) vary from one material to another, especially during the size reduction stage, waste can be separated by size to facilitate material sorting.

Crushing

After being separated and sorted, the plastics are crushed into small pieces called flakes or chips. This step facilitates the transportation and subsequent processing of the material for reuse.

Density Separation

Plastics can then be separated by density through a process called flotation separation. In this step, the plastics are placed in a tank of water and agitated to separate them by density.

The lighter plastics float on the surface of the water, while the heavier polymers sink to the bottom of the tank.

Cleaning and Drying

After being separated, the plastics are cleaned and dried to remove contaminants and reduce the risk of degradation during the recycling process.

Melting and Molding

Finally, the plastics are melted and molded into new products such as bottles, bags, and containers.