Chemical Recycling of Post-consumer Polylactide Products by Microwave-Assisted Aminolysis with Ethylenediamine

Jetawat Wadputi, Atitsa Petchsuk, Mantana Opaprakasit, Pakorn Opaprakasit — Tue, 08 Apr 2025 00:00:00 +0700

The demand for bioplastics has recently increased as a promising alternative to conventional plastics due to their degradability, renewability, and excellent properties compared to their fossil-based counterparts. Although these materials are degradable, recycling their post-consumer products is considered effective and sustainable, especially by converting them into value-added feedstocks or starting materials for other processes. In this work, a chemical recycling process for polylactide (PLA) by aminolysis depolymerization is developed, employing a diamine as a nucleophile to cleave the ester bonds of PLA. The process utilizes microwave irradiation and ethylenediamine (EDA) as a reactant. The effects of the PLA/EDA feed ratio on the chemical structures and compositions of the aminolyzed PLA oligomers are investigated by ATR-FTIR and ¹H-NMR spectroscopy. The chemical structures and average length of the lactate sequences are determined. The product mixture consists of amino-capped lactate sequences of different lengths, i.e., mono-lactate, di-lactate, and poly-lactate. These are classified into two structures: Structure A is generated when a single -NH₂ of EDA reacts and attaches to lactate sequences, while Structure B is formed when both amine groups react. At a low PLA/EDA feed content of 5:1, the aminolyzed products consist of 91% Structure A content with the shortest average lactate length of 0.9 units, as the high EDA feed content effectively enables its -NH₂ groups to compete with each other to convert the ester bonds of PLA. When the feed ratio was increased to 30:1, Structure B became a major product at 85%, with an average lactate length of 11.1, due to the deficit of -NH₂ groups in the system. The variation in these reaction parameters enables the synthesis of products with tunable structures for use in specific applications. The developed process is promising for converting PLA waste, with a short reaction time, into starting materials for other value-added products, especially lactide-based polyurethanes.

Porous Poly(methyl methacrylate) Microsphere via Suspension Polymerization: Synthesis, Characterizations, and the Effect of Triglycerides as Porogen

Nutchanon Putthabucha, Saran Salakij, Piyachai Khomein — Thu, 20 Feb 2025 00:00:00 +0700

Porous microspheres with interconnected internal and external pores can provide a large specific surface area, making them excellent adsorbents for various applications such as controlled drug release, chromatography, tissue engineering scaffolds, and blood purification. Poly(methyl methacrylate) (PMMA) has been globally utilized in many medical applications (e.g., adsorbents, drug delivery, dental implants, etc.) due to its unique properties including good thermal and chemical stability, biocompatibility, and hemocompatibility. In this work, we developed a method to prepare PMMA porous microspheres using triglycerides as porogen via suspension polymerization yielding particle size of 300-500 µm with a specific surface area as high as 281 m²×g^-1. In addition, we also investigated the effect of triglycerides ranging from short-, medium-, and long-chain triglycerides as a porogen, which can influence the morphology and mechanical stability of the microspheres. The microspheres were characterized through an optical microscope and scanning electron microscope on morphology. In addition, pore size, pore volume, and specific surface area were calculated by BET method. The porosity of the microspheres was observed to be dependent on the type of triglycerides, where the short chain provided the highest porosity and the long chain provided the lowest porosity.

Keywords: Porous microspheres, Poly(methyl methacrylate) (PMMA), Triglycerides porogen, Suspension polymerization

SIAM: Science and Innovation of Advanced Materials

Chemical Recycling of Post-consumer Polylactide Products by Microwave-Assisted Aminolysis with Ethylenediamine

Porous Poly(methyl methacrylate) Microsphere via Suspension Polymerization: Synthesis, Characterizations, and the Effect of Triglycerides as Porogen