We reviewed the current state of the art of poly(ethylene terephthalate) (PET) chemolysis used in the chemical recycling of PET.

A series of heteroarm amphiphilic molecular brushes (AMBs) with poly­(ethylene glycol) (PEG) and long chain n-alkyl side chains were synthesized via conventional free radical polymerization (FRP) of mainly 4-vinylbenzyl-PEG methyl ether and N-alkylmaleimide macromonomers. By varying PEG side chain degree of polymerization (DP = 12, 16, and 20) and n-alkyl chain lengths (C16 and C20), we produced AMBs with varying combinations of side chain lengths. This enabled the elucidation of the effect of side chain length on AMB phase behavior, semicrystalline morphologies, and crystallization kinetics via differential scanning calorimetry, polarized light optical microscopy, and X-ray diffraction experiments. Calculations of segregation strength together with SAXS measurements indicate that all materials have probably phase-segregated structure in the melt. Most of the AMB materials prepared were double crystalline, i.e., contained crystals from alkyl and PEG chains. AMB crystallization was constrained by AMB architecture, the frustration being most evident in AMBs with combinations of either low DPPEG or short alkyl chain lengths. Large, well-developed spherulites, implying breakout crystallization from a weakly segregated melt, were only observed for the AMBs with the combination of the longest PEG chain (DP = 20) and longest alkyl chain length (C20). A peculiar behavior was found when spherulitic growth rates and overall crystallization rates of the PEG chains, within this particular AMB sample, were determined to be a function of crystallization temperature. In both cases, a distinct minimum with decreasing temperature was observed, probably caused by the challenges encountered in crystal packing of the PEG side chains, tethered to an amorphous backbone, which also contained already crystallized C20 chains. This minimum is analogous to that observed in the crystallization of long chain n-alkanes or high molar mass polyethylenes with bromine pendant groups that has been attributed to a self-poisoning effect; this is the first observation of this phenomenon in AMBs.

Mixed plastic waste-streams are a main obstacle to a more extensive implementation of polymer recycling. Separating mixed-plastic waste streams demands time and effort at collection or in the recycling plant, while many products consist of multiple polymers that cannot be readily separated. Chemical recycling could provide the key to overcome this issue by targeting specific chemical bonds, enabling selective depolymerization of a single polymer class in a mixture. This work explores the depolymerization of polycarbonate (PC) and polyethylene terephthalate (PET) in separate and in mixed streams. Selective depolymerization of mixed streams composed of PET and PC and one-step separation of their constituent monomers are carried out with outstanding energy efficiency through an inexpensive KOH-in-methanol hydrolysis (KMH) process developed for instantaneous PET hydrolysis. The activation energies for depolymerization of PC and PET pellets are 68.6 and 131.4 kJ mol À 1 , respectively. Randomly mixed streams are fully depolymerized within 2 min at 120 °C using 30 mL of depolymerization solution per gram of polymer. The separation of bisphenol A and terephthalic acid is demonstrated in a onestep separation process, yielding 98 and 97 % purity without any secondary reactions detected. Simultaneous depolymerization and selective one-step separation of monomers are also demonstrated for a PET/PC polymer blend prepared by solution casting, showing that this process also works for intimately mixed PET/PC mixtures.

Treatment of limescale build-up in process-and municipal pipes by magnetic water treatment has been a topic of research for decades. However, there is no realistic mechanistic hypothesis as to why such treatments would be effective. Therefore, a test regime was established to explore scale inhibition by means of magnetic forces in a robust and reproducible manner. In this study, two magnetic devices were developed using Neodymium-based rare earth magnets for the application of static magnetic fields. One device, based on a Halbach array, is designed to test high-intensity (965 mT) magnetic fields. The other is based on a Halbach trap arrangement, designed to test high magnetic field gradients (490 mT, 82.5 T/m). The precipitation reactions of calcium carbonate, calcium sulfate, and calcium phosphate were monitored in real-time to determine the effectiveness of these devices for inhibiting scale. No magnetic treatment effects were observed.