Recycling of Polymer Waste Using Different Techniques

2023-1-26
Sivri, Seda
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Polylactic acid (PLA) is the most widely known renewable biodegradable polymer due to its mass production, good processability, optical, mechanical, thermal, and barrier properties. Hence, the production rate of PLA increased gradually during the last decade. However, PLA is known to have slow degradation rate in soil and marine environments, leading to significant waste accumulation with widespread usage of the polymer. Thus, recycling of PLA waste will become a significant environmental concern in near future unless the effective techniques emerge. Focusing on this problem, the degradation of PLA was performed with and without metal loaded silica aerogel catalysts using custom-designed pyrolysis system and high-pressure reaction system under different reaction parameters. The production of lactide isomers, lactic acid, propionic acid, acetaldehyde, carbon monoxide, carbon dioxide and hydrogen were achieved. The maximum lactide isomer yield was determined to be 49 wt.% at 225 °C, 480 min, 70 rpm under 50 ml/min argon flow in pyrolysis system, while 89 wt.% lactide isomer yield was achieved at 200 °C, 120 min, 70 rpm and 206 bar in high-pressure system. In addition, Al, Fe, and Mg loaded catalysts were found to be effective in the degradation of PLA. The highest lactide isomer yield was found to be 58 wt.% with SAUFe15 catalyst at 225 °C, 60 min, 70 rpm under 50 ml/min argon flow. These outputs show that supercritical carbon dioxide medium, mesoporous catalysts and pyrolysis technique are promising for the recycling of PLA with the aim of closed loop production of PLA.
Polylactic Acid, Degradation, Pyrolysis, Supercritical Carbon Dioxide, Mesoporous Catalysts
https://hdl.handle.net/11511/102570
Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats
S. Sivri, “Recycling of Polymer Waste Using Different Techniques,” Ph.D. - Doctoral Program, Middle East Technical University, 2023.
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