Novel Strategies for Recycling Poly(butylene adipate-co-terephthalate)-Starch-Based Plastics: Selective Solubilization and Depolymerization–Repolymerization Processes

Abstract

Starch-based plastics (SBPs) containing poly-(butylene adipate-co-terephthalate) (PBAT) are among the most produced bioplastics on the market and are currently managed at their end of life (EoL) through composting. In view of developing novel EoL approaches, SBPs were characterized here in terms of their main components (PBAT, starch, and plasticizer), and three strategies for their recycling were investigated: (I) the selective solubilization of PBAT with ethyl acetate; (II) a two-step depolymerization−repolymerization process that consists of the catalytic selective alcoholysis of PBAT into its oligomers, followed by their repolymerization to PBAT with no need of adding a new catalyst; and (III) the complete selective depolymerization of PBAT, followed by the recovery and purification of butanediol (1,4-BD), dimethyl terephthalate (DMT), and dimethyl adipate (DMA). Up to 99, 95, and 93% recovery of the SBP components was obtained, respectively, following these three methods. Extensive characterization of the recovered PBAT was performed through molecular weight and thermal and thermomechanical analyses, demonstrating the efficiency of the processes. The environmental sustainability of the proposed approaches was also preliminarily evaluated through the calculation of their environmental factor (E-factor).

Amine-Grafted Heterogeneous Catalysts from Waste for Diols Conversion into Cyclic Carbonates

“…While the overall composition could be considered similar, some differences appear in the carbon and nitrogen content of the chars depending on the starting material: SBP char shows a lower quantity of carbon than the other chars, already from the first pyrolysis step (entry 4, Table ). This behavior, already observed in other works, , may be due to the chemical composition of SBP: in addition to starch, corresponding to 28% of the total weight and responsible of the majority of the char produced, the main component is poly(butylene adipate- co -terephthalate) (64%), PBAT, a copolyester that, if subjected to pyrolysis, tends to form a less amount of char than starch, as already observed and confirmed by the lowest pyrolysis yield with respect to the other materials (see SI, Table S1); 4–6% of plasticizer (usually sorbitol); 2–4% of inorganic compounds (including CaCO 3 and TiO 2 as major components), which are responsible for decreasing the carbon content as they remain in the char fraction PUCF char shows a higher N amount than the other chars (1.14 vs 0.1 %) due to the presence of amines, like nicotine and cotinine, adsorbed on post-use cigarette filters, released upon tobacco combustion (entry 6, Table ).…”

“…This behavior, already observed in other works, 23,31 may be due to the chemical composition of SBP: in addition to starch, corresponding to 28% of the total weight and responsible of the majority of the char produced, the main component is poly(butylene adipate-co-terephthalate) (64%), PBAT, a copolyester that, if subjected to pyrolysis, tends to form a less amount of char than starch, as already observed and confirmed by the lowest pyrolysis yield with respect to the other materials (see SI, Table S1); 4−6% of plasticizer (usually sorbitol); 2−4% of inorganic compounds (including CaCO 3 and TiO 2 as major components), which are responsible for decreasing the carbon content as they remain in the char fraction. 34 • PUCF char shows a higher N amount than the other chars (1.14 vs 0.1 %) due to the presence of amines, like nicotine and cotinine, adsorbed on post-use cigarette filters, released upon tobacco combustion (entry 6, Table 2). 35−37 Due to the presence of non-negligible nitrogen content, the C-PUCF was tested in the CIR to verify if a further amination step was still necessary: no CC was observed, demonstrating the need to perform the second step.…”

Enhancing the Mechanical Properties of PBAT/Thermoplastic Starch (TPS) Biodegradable Composite Films through a Dynamic Vulcanization Process

“…As a result, it serves as an excellent alternative to polyethylene (PE) in film packaging. − However, PBAT has higher production costs compared to conventional nonbiodegradable PE or polypropylene (PP), which limits its widespread application in the film industry. An urgent challenge is to reduce the cost of PBAT products without compromising their biodegradability, and one effective approach is to incorporate natural, low-cost materials. − …”