Structure and characterization of random aliphatic–aromatic copolyester

One-Pot Depolymerization of Mixed Plastics Using a Dual Enzyme System

As global plastic consumption and littering escalate, innovative approaches to sustainable waste management are crucial. Enzymatic depolymerization has emerged as a promising recycling method for polyesters via monomer recovery under mild conditions. However, current research mainly focuses on using a single plastic feedstock, which can only be derived from complex and costly plastic waste sorting. This study investigated the enzymatic depolymerization of mixed plastics using a dual-enzyme system in a one-pot approach. Employing the polyester hydrolase PES-H1 FY and the (poly)urethanase UMG-SP-2, mixed or blended polymers consisting of polyethylene terephthalate (PET), polybutylene adipate-co-terephthalate (PBAT), and thermoplastic polyester-polyurethane (TPU) were depolymerized into their monomers. Chromatographic quantification revealed a total yield of monomeric products of up to 39.8±4.4 % after 96 h reactions, which was consistent with the weight loss measurements of 40.9±2.5 %. In addition, a modified dissolution-precipitation method was shown to easily blend the three different polymers while improving their degradability. Our findings suggest that using mixed enzymes is a viable method for recycling mixed or blended waste plastics without polymer sorting. Individual monomers can be separated and purified to produce virgin polymers, while their mixture in the hydrolysate can easily serve as feedstock for microbial upcycling into value-added products.

Exploring the potential of lignin nanoparticles in enhancing the mechanical, thermal, and bioactive properties of poly (butylene adipate-co-terephthalate)

The preparation and characterization of lignin nanoparticles (LNPs) were described. LNPs were produced via the precipitation technique. Nanocomposites of LNPs with poly (butylene adipate-co-terephthalate) (PBAT) were prepared by melt mixing with various concentrations up to 6 wt% of LNPs. The assessment of the effects of LNP addition on the mechanical, thermal, morphological, cytotoxicity, antioxidant, antibacterial, and antiviral properties of nanocomposites was carefully performed. The addition of LNPs to PBAT enhances the thermal stability of the nanocomposites. The antioxidant effect of LNPs on PBAT increased with increasing filler content. LNPs showed higher efficiency as antioxidant agents than lignin particles (LP). The tensile modulus increased by 20 % for the nanocomposites with 6 % LNPs in comparison with neat PBAT. The crystallization peak temperature of PBAT was 80 °C, which increased to 104.6 °C with the addition of 6 wt% of LNPs, suggesting their strong nucleation activity. Antibacterial tests demonstrated the bacteriostatic activities of LNP, LP, and nanocomposites. Both LP and LNP showed considerable antiviral activity against herpes simplex virus type 1 and human coronavirus 229e. The antiviral activity of LNP was concentration-dependent. The findings suggest that LNP is a promising bio-additive for PBAT and can enhance its properties for various applications, including food packaging.

Shear-Induced and Nanofiber-Nucleated Crystallization of Novel Aliphatic-Aromatic Copolyesters Delineated for In Situ Generation of Biodegradable Nanocomposites

The shear-induced and cellulose-nanofiber nucleated crystallization of two novel aliphatic-aromatic copolyesters is outlined due to its significance for the in situ generation of biodegradable nanocomposites, which require the crystallization of nanofibrous sheared inclusions at higher temperatures. The shear-induced non-isothermal crystallization of two copolyesters, namely, poly(butylene adipate-co-succinate-co-glutarate-co-terephthalate) (PBASGT) and poly(butylene adipate-co-terephthalate) (PBAT), was studied following a light depolarization technique. To have a deep insight into the process, the effects of the shear rate, shear time, shearing temperature and cooling rate on the initiation, kinetics, growth and termination of crystals were investigated. Films of 60 μm were subjected to various shear rates (100-800 s-1) for different time intervals during cooling. The effects of the shearing time and increasing the shear rate were found to be an elevated crystallization temperature, increased nucleation density, reduced growth size of lamella stacks and decreased crystallization time. Due to the boosted nucleation sites, the nuclei impinged with each other quickly and growth was hindered. The effect of the cooling rate was more significant at lower shear rates. Shearing the samples at lower temperatures, but still above the nominal melting point, further shifted the non-isothermal crystallization to higher temperatures. As a result of cellulose nanofibers' presence, the crystallization of PBAT, analyzed by DSC, was shifted to higher temperatures.

In situ generation of sustainable PLA-based nanocomposites by shear induced crystallization of nanofibrillar inclusions

In situ formation of polymer nanofibrils during compounding with a second polymer followed by their immediate solidification due to shear induced crystallization for two pairs of polymers is described.

Poly(butylene succinate-co-terephthalate) nanofibrous membrane composited with cyclodextrin polymer for superhydrophilic property

Tailoring the wetting properties of nanofibrous membranes and endowing them with expected wettability provides new ways in extending the application field of these materials. In this study, we first performed the in situ fabrication of poly(butylenes succinate-co-terephthalate) (PBST) composite nanofibrous membrane with cyclodextrin polymer (CDP) using a combination of electrospinning and heating processes. Then, the morphologies, crystallization and mechanical properties of the PBST composite membrane were investigated. It was found that the CDP was uniformly dispersed on the PBST nanofibers instead of merely covering the surface of the membrane. Moreover, the introduction of additives brought about a decreased crystallinity and tensile strength of the resultant membrane due to its restraining role in the crystallization of PBST. Furthermore, the wettability of the PBST composite membranes with various amounts of additives was explored and the evolution of water spread on top of the membranes was also recorded. The membrane became superhydrophilic from hydrophobic upon increasing the amount of additives and the water droplet could completely spread within 0.2 s, which was attributed to the enlarged roughness and increased contact area of CDP on the nanofibers. A comparison between the two fabrication methods used for PBST composite nanofibrous membranes is also presented and studies on the preparation and wetting properties may shed light on polymer composite membranes that exhibit potential application in more fields.

We present a facile fabrication method for a PBST composite nanofibrous membrane with cyclodextrin polymer via electrospinning and heating processes. The membrane is superhydrophilic and water can completely spread on the surface within just 0.2 s.

Antimicrobial and sustainable food packaging based on poly(butylene adipate-co-terephthalate) and electrospun chitosan nanofibers

PBAT/CS-NF bionanocomposites show an optimal combination of flexibility, strength, barrier, migration, and antibacterial properties, therefore are suitable for food packaging applications.