2025/01/03 by Ruben Goldhahn, Ann-Joelle Minor, Liisa Rihko‐Struckmann +4 · 1 voice
Materials Science · Environmental Science · #Polymer Science and PVC #biodegradable polymer synthesis and properties #Recycling and Waste Management Techniques
paper · pdf · doi:10.3390/recycling10010005
openalex publication_date 2025/01/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/23
To address the problems of virgin plastic production from fossil resources and the growing amount of plastic waste, a rapid transition to a circular economy is being pursued. The separation of mixed plastics into pure fractions is of paramount importance for promoting recycling and preventing downcycling. In this study, experimental parameters were determined for the selective bulk dissolution of polyamide 6 (PA 6) filaments (1.75 mm diameter, 1 cm length) in CaCl2-EtOH-H2O mixtures (CEW) at 75 °C. These parameters included the energy supply mode, dissolution time, CEW composition and CEW:PA mass ratio. Compared with energy supply by microwaves, energy supply by ultrasound improved the yield of dissolved and recovered PA 6 after 5 h from 31% to 52%. In total, the yield of PA 6 after 3 h of bulk dissolution increased from 18% to 69% when the energy supply mode was changed from microwave to ultrasound and the H2O:EtOH molar ratio of CEW was increased from 0.40 to 1.33 while maintaining an optimal CEW:PA mass ratio of 8.5. Additionally, master plot analysis suggested that dissolution under microwave energy supply followed a contracting cylinder model, whereas dissolution under ultrasonic energy supply aligned with a 2D diffusion or third-order kinetic model. Microscopic observations suggested that, in the case of ultrasonic energy supply, oscillating bubbles on the particle surface enhanced the dissolution rate of PA 6 filaments in CEW.