Sorting plastics with light
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A new technology able to automatically identify different type of plastic could significantly speed up the sorting process while also reducing instances of human error.
The system will identify the plastic types by exposing the pieces to a flash of light, which will cause them to fluoresce. That light will then be read by photoelectric sensors, which will measure how long it takes the fluorescent light to fade. Since the polymer materials used to make plastic items have specific fluorescence lifetimes, the plastic type can be identified by its decay curve. With this process, errors in measurement will practically be ruled out; for any given material, one will always obtain the same value for the fluorescence half-life, just as in the case of radioactive decay.