(322d) Transient Thermal Barcode: A High Speed, High Throughput Plastic Sorting Based on Molecular Vibrational Signature.

While the production of plastic has increased exponentially over the years, from 2.3 million tons in 1950 to 448 million tons by 2015, the overall recycling rate of waste plastic has grown only to 8.7%. The first step towards efficient recycling is the accurate identification of each type of the 6 types of recyclable plastic. At present, the most effective sorting methods in the market are based on NIR, Raman spectroscopy & AI-assisted sorters. NIR spectra have overtones which increase the chances of false identification whereas Raman signals are very weak and require high-power lasers. AI-assisted sorting robots can sort materials based only on their visible characteristics, but cannot provide chemical information. Hence there is an urgent need to develop a novel technique which can sort plastic waste in a high throughput fashion that can be easily implemented in Material Recycling Facility (MRF). To address the abovementioned challenges, we have developed technique of plastic sorting called the Transient Thermal Barcode (TTB). The TTB technique is based on imaging localized heat generated by mid-IR absorption (photothermal effect). In the mid-Infrared region, called the ‘molecular fingerprint regime’ due to the absence of overtones, different plastics have unique spectral peaks. When IR with the matching wavelength is incident on the plastic, molecules are resonantly excited into higher vibrational states. Non-radiative decay of the excited states generates localized heating on the plastic. Projecting IR light patterns with multiple characteristic spectral peaks on the plastics generates photothermal heat patterns (Barcodes) characteristic to each of the 6 recyclable plastics including black plastic. We have demonstrated that imaging the plastic with an IR camera can identify different plastics based on their barcode heat pattern. This TTB technique has the potential for high throughput sorting of waste plastic in MRFs and secondary recycling facilities.

Acknowledgement: - This work was supported by the NYS-DEC Initiative for Plastics Recycling Research and Innovation, University at Buffalo. (Website: - https://www.buffalo.edu/iprri.html )