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A process for the chemical recycling of degradable polylactide (PLA) has been developed, to convert its disposable wastes into small-sized products for further use as value-added starting materials for specialty products. A microwave-assisted alcoholysis reaction, using diols and tetrabutyl orthotitanate (TBT) catalyst, was employed. The effects of the types of diols and PLA/diol feeding ratios on the structures and properties of the resulting alcoholized products were examined by using ethylene glycol (EG), propane-1,3-diol (PDO), and butane-1,4-diol (BDO). The PLA/diol ratios were varied from 1:1 to 4:1 wt/wt. The products were characterized by ATR-FTIR, 1H NMR, and 2D-NMR HMQC and HMBC spectroscopy. The products compost to diol-capped lactate sequences with different lengths, i.e., lactate, lactyllactate, and poly-lactate. The yield of the shortest lactate was about 65% for the LBDOT11 system, and 90% for the LEGT11 and LPDOT11 systems, when a feeding ratio of 1:1 wt/wt was employed. The yield decreased with an increase in the ratios, from 1:1 to 4:1 wt/wt. In contrast, the yields of longer lactyllactate and poly-lactate increased with an increase in the ratios. In terms of OH-endcapping efficiency, the products have two structures: (A) LA-O-(CH2)x-OH and (B) LA-O-(CH2)x-O-LA. The contents depend on diol types and the PLA/diol feeding ratio. The alcoholized products were then used as starting polyols in the preparation of lactide-based polyurethanes (PUs) by reacting with 1,6-diisocyanatohexane (HDI) and BDO chain extender. The resulting PUs exhibit promising mechanical and thermal properties. These PUs are suitable for use as either single-component materials, e.g., 3D-printing filaments and degradable adhesives, or as toughness-enhancing agents for brittle polymers, especially PLA.

Aliphatic/aromatic copolyesters, which possess good mechanical property and degradability, are of immense interest. Standard characterization techniques for the copolymer structure and degradation behaviors have been developed. The techniques are applied to examine hydrolytic degradation of poly(ethylene terephthalate- co -lactic acid) in a phosphate buffer solution (pH 7.2) at 60 °C. The weight loss of the copolymer and pH of the medium as a function of time are examined. 1 H NMR spectra provide information on microstructure and molecular weight of the samples, where deviations of the results from the actual values are observed, due to low solubility of the copolymer. More accurate results are obtained from TGA and FTIR experiments, as the samples are characterized in bulk. Insight into degradation mechanisms of the copolymer is derived from FTIR spectra. The content of aromatic esters in the soluble degraded species is determined from UV–Vis spectroscopy. These standard methods can be applied to various types of degradable aliphatic/aromatic copolyesters, which are essential in property assessment and determination of their potential applications.