There are several technologies that can separate plastics from a mixed waste stream and then sort the result by plastic type. Since a product’s design can influence the effectiveness of these processes it is important that designers and manufacturers consider them.

These are the key technologies that are currently used to separate plastic scrap:

Sink-Float Density Separation

Mixed plastic waste is introduced to a flotation bath. The plastics are separated based on their density relative to that of the fluid that they are in. Some plastics will sink in the liquid, while others will float.

X-Ray Technology

X-rays are used to distinguish between different types of polymers according to their density.

Near Infrared Spectroscopy

When plastics are illuminated, they mostly reflect light in the near infrared (NIR) wavelength spectrum. A NIR sensor can distinguish materials based on how they reflect light. An air jet is used to blow materials into separate streams. NIR Spectroscopy is less suitable for dark coloured plastics since these absorb nearly all light.