Reducing Antisolvent Use in the STRAP Process by Enabling a Temperature-Controlled Polymer Dissolution and Precipitation for the Recycling of Multilayer Plastic Films

Multi-Functional Organofluoride Catalysts for Polyesters Production and Upcycling Degradation

The production and degradation of polyesters are two crucial processes in polyester materials' life cycle. In this work, multi-functional organocatalysts based on fluorides for both processes are described. Organofluorides were developed as catalysts for ring-opening polymerization of lactide (lactone). Compared with a series of organohalides, organofluoride performed the best catalytic reactivity because of the hydrogen bond interaction between F- and alcohol initiator. The Mn values of polyester products could be up to 72 kg mol-1 . With organofluoride catalysts, the ring-opening copolymerization between various anhydrides and epoxides could be established. Furthermore, terpolymerization of anhydride, epoxide, and lactide could be constructed by the self-switchable organofluoride catalyst to yield a block polymer with a strictly controlled polymerization sequence. Organofluorides were also efficient catalysts for upcycling polyester plastic wastes via alcoholysis. Mixed polyester materials could also be hierarchically recycled.

Decohesion of a polyolefin overlay from a substrate high density polyethylene layer by impact induced stress waves

High-density polythene (HDPE) is difficult to separate from food packaging waste for recycling because the packaging occasionally has multilayer plastic labels attached. Solvents are employed in the current separation techniques to remove undesirable layers from HDPE substrates. The possibility of separating HDPE via the impact-delamination phenomenon was explored both theoretically and experimentally. Using the cohesive zone model (CZM), the decohesion of layers in a model two-layer laminate made of HDPE and LDPE layers was studied theoretically. According to this study, stress waves emerge and severely damage the adhesion between the layers as a cutting blade strikes the laminate at speeds greater than 40 m/s. The damage can be enhanced by increasing the strike velocity and the apex radius of the blade. These findings show that a novel plastic delaminator that can cut and delaminate the laminates simultaneously can be designed. The proposed machine will feature two sets of blades with varying edge apex radii. One set of blades can be designed to cause the most adhesion damage while the other blades cut the laminate. This unique combination of cutting and delamination operations has several benefits, including less solvent waste and downstream processes, greater environmental friendliness, and faster HDPE separation. Laminates from HDPE milk bottles were cut using a high-speed cutter-blender with six blades to test the predicted results. The cut HDPE flakes were separated pneumatically. According to FTIR analysis and SEM, only a trace of adhesive was present on the cut and separated HDPE flakes.

Evaluation of mixed #3-7 plastic waste from material recovery facilities (MRFs) in the United States

Plastic recycling rates are still low in the United States (U.S.), with less than 10% of municipal solid waste (MSW) plastic being recycled. Most unrecycled plastics are identified by Resin Identification Codes (RIC) from #3-7, which are commonly destined for landfill or waste-to-energy facilities (WTE). Therefore, the composition and quality of outbound bales containing #3-7 plastics were assessed to understand the potential to increase recycling rates. Three bales were sourced from three different Material Recovery Facilities (MRFs) located in the United States. Each bale was manually sorted and characterized for quality and performance via multiple plastic characterization techniques. Considerable differences in bale composition were observed between MRFs, which correlated with the technology used by each MRF in the sorting process. The differences were substantial in the residual levels of poly(ethylene terephthalate) (PET) and high-density polyethylene (HDPE), which are highly desired for mechanical recycling processes and not expected in #3-7 plastics bales. Traditional recycling processes including washing, extrusion, and injection molding of the sorted material were employed prior to the physical, thermal, and molecular characterization. Despite differences in bale composition by plastic type, some polymer properties were similar across MRFs. This research suggests that landfill-diverted mixed plastic waste can be utilized in the mechanical recycling of currently unrecycled materials, as processes can be designed to work with consistent polymer properties. It also highlights the need to upgrade the sorting systems to prevent waste feedstocks, which can be recycled with current technologies, from contaminating other plastic streams or reach landfills.

COSMO-RS blind prediction of distribution coefficients and aqueous pKa values from the SAMPL8 challenge

The SAMPL8 blind prediction challenge, which addresses the acid/base dissociation constants (pKa) and the distribution coefficients (logD), was addressed by the Conductor like Screening Model for Realistic Solvation (COSMO-RS). Using the COSMOtherm implementation of COSMO-RS together with a rigorous conformational sampling, yielded logD predictions with a root mean square deviation (RMSD) of 1.36 log units over all 11 compounds and seven bi-phasic systems of the data set, which was the most accurate of all contest submissions (logD).For the SAMPL8 pKa competition, participants were asked to report the standard state free energies of all microstates, which were then used to calculate the macroscopic pKa. We have used COSMO-RS based linear free energy fit models to calculate the requested energies. The assignment of the calculated and experimental pKa values was made on the basis of the popular transitions, i.e. the transition hat was predicted by the majority of the submissions. With this assignment and a model that covers both, pKa and base pKa, we achieved an RMSD of 3.44 log units (18 pKa values of 14 molecules), which is the second place of the six ranked submissions. By changing to an assignment that is based on the experimental transition curves, the RMSD reduces to 1.65. In addition to the ranked contribution, we submitted two more data sets, one for the standard pKa model and one or the standard base pKa model of COSMOtherm. Using the experiment based assignment with the predictions of the two sets we received a RMSD of 1.42 log units (25 pKa values of 20 molecules). The deviation mainly arises from a single outlier compound, the omission of which leads to an RMSD of 0.89 log units.

Sustainability of Synthetic Plastics: Considerations in Materials Life-Cycle Management

The sustainability of current and future plastic materials is a major focus of basic research, industry, government, and society at large. There is a general recognition of the positive impacts of plastics, especially packaging; however, the negative consequences around end-of-life outcomes and overall materials circularity are issues that must be addressed. In this perspective, we highlight some of the challenges associated with the many uses of plastic components and the diversity of materials needed to satisfy consumer demand, with several examples focused on plastics packaging. We also discuss the opportunities provided by conventional and advanced recycling/upgrading routes to petrochemical and bio-based materials and feedstocks, along with overviews of chemistry-related (experimental, computational, data science, and materials traceability) approaches to the valorization of polymers toward a closed-loop environment.