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Microwave-assisted chemical recycling of polylactide by aminolysis for functional materials |
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| รหัสดีโอไอ | |
| Title | Microwave-assisted chemical recycling of polylactide by aminolysis for functional materials |
| Creator | Jetawat Wadputi |
| Contributor | Pakorn Opaprakasit, Advisor |
| Publisher | Thammasat University |
| Publication Year | 2568 |
| Keyword | Chemical recycling, Aminolysis, Polylactide, Microwave-assisted, Circular economy |
| Abstract | Chemical recycling of degradable material is considered an effective and sustainable strategy for recycling their post-consumer products by converting them into value-added feedstocks or starting materials. In this work, a chemical recycling process for polylactide (PLA) has been developed via aminolysis depolymerization by employing ethylenediamine (EDA) as a diamine nucleophile to cleave the ester bonds of PLA under microwave irradiation. The resulting aminolyzed products were targeted as starting materials for synthesizing lactide-based polyurethanes. The PLA/EDA feed ratios were varied from 5:1, 10:1, 20:1, 25:1, and 30:1 wt/wt. The effects of these varying ratios on the chemical structures and compositions of the aminolyzed PLA oligomers were investigated using ATR-FTIR and 1H-NMR spectroscopy. The resulting products consisted of amino-capped lactate sequences of different lengths, i.e., mono-lactate, di-lactate, and poly-lactate, which are classified into two distinct structures. Structure A is generated when a single -NH2 of EDA reacts with a lactate sequence, whereas Structure B is formed when both amine groups react. At a low PLA/EDA feed content of 5:1, the aminolyzed product consisted predominantly of Structure A (91%), with the shortest average lactate length of 0.9 units. This was attributed to the high EDA content, which enabled strong competition of –NH2 groups for ester bond cleavage. In contrast, at a high PLA/EDA ratio of 30:1, Structure B became a major product (85%) with an average lactate length of 11.1units, due to the relative deficit of available –NH2 groups. These demonstrate that the product composition strongly depends on the PLA/EDA feed ratio. The aminolyzed product with 25/1 (PLA: EDA 25/1) was then selected as precursor starting material in preparation of lactide-based polyurethanes by reacting with isophorone diisocyanate (IPDI) and polyethylene glycol (PEG2000) chain extender. The resulting PUs exhibit promising mechanical and thermal properties, indicating their potential as multifunctional materials, particularly as degradable adhesives for advanced applications. |
