Separation Of Polymers Research Articles

Effect of Joining Mechanism on the Mechanical Recycling of Polymer–Metal Composite Parts

In order to be able to recycle composite components made of polymer and metal, which are used in the automotive industry, the joints must be broken. The success of the separation is influenced by the stress and also by the joining mechanism between the polymer and the metal. Here, force-fit and form-fit connected components are produced and crushed in a rotor impact mill with two different rotors. The results show that the crushing results differ significantly for the different rotors and for the various joining processes. In short, the hammer-type rotor provides much finer and better-separated fragments and the force-fit joints enable a better separation of metal and polymers. The additional cooling of the samples also changes the result in a way, where deep cooling significantly improves the separation of the metal and the polymer. Different types of polymers also led to a different separation result with both rotors.

Locking organic solvents by crystallization-induced polymer network

Organogels that lock organic solvents within a polymer network shows promising applications in ice-phobicity, anti-biofouling, conserving cultural heritage etc. However, the synthesis of organogels by versatile and cost-effective methods still remain challenging. Here, we introduce a novel and economical approach to organogel preparation via crystallization-induced polymer precipitation, which involves the straightforward blending of carbonyl contained polymer, nano Ca(OH)2, and excess ethyl acetate (EA). During the formation, nano Ca(OH)2 reacts with EA to produce ethanol and calcium acetate, in which Ca2+ ionically bonds with carbonyl of polymer. Due to the low solubility in EA and ethanol, calcium acetate initiates crystallization. The interaction between Ca(CH3COO)2 and polymer induces the separation of polymer from the solvent, thereby forming a network that locks the surplus EA and ethanol. More importantly, the organogel is capable not only of encapsulating 12 organic solvents within its precursor but also of effectively removing various aged polymeric coatings from wall paintings without leaving residues. This innovative organogel system marks a significant forward in the realm of organogel with applications in conservation and surface engineering.

Screening of the biphenyl polyamides nanofilms appropriate for molecular separation in organic solution feed

Developing polymeric separation membranes that combine excellent solvent stability, high permeability, and customizable molecular weight interception remains a challenge. Herein, thin-film composite (TFC) polyamide (PA) membranes with poly(ether ether ketone) (PEEK) support and biphenyl-centered polyamides active layer were fabricated through interfacial polymerization technique for the first time. Enhanced solvent stability was exhibited by the fabricated membranes due to the intrinsic resistance to organic solvents possessed by PEEK and biphenyl polyamides. The separation performance of the obtained membranes was systematically studied by relating to the properties of PA nanofilms in terms of nano-mechanical strength, morphologies, and microporosity. The organic solvent nanofiltration (OSN) performance of the resultant membranes in terms of permeability and molecular weight cut-off (MWCO) could be regulated. The optimized membrane exhibited a pure solvent permeability as high as 21.6 L m−2 h−1 bar−1 for acetonitrile and 14.0 L m−2 h−1 bar−1 for methanol. It also showed excellent long-term durability with almost unchanged permeability as well as solute retention remained above 97.8 % after a cumulative OSN operation of N, N-Dimethylformamide (DMF) based feed for 240 h. In particular, OSN membrane with targeted MWCOs covering the range of 170–370 g·mol−1 could be fabricated by selecting appropriate biphenyl acyl chlorides as building blocks. This approach offers a scalable and versatile platform for the development of solvent-stable, highly permeable, and customizable MWCO membranes for process-oriented OSN.

In situ hydrolyzed microporous polymer membranes for additional free volume to facilitate CO2 permeation

Advancements in membrane separation technology play a pivotal role in separation processes closely associated with the environment and energy. However, presently available commercial polymeric membranes encounter the challenge of low permeability, impacting both separation efficiency and membrane module costs. Here, we propose a simple and effective in situ acid hydrolysis strategy to significantly enhance membrane permeability. Specifically, a tetrafluorinated monomer with hydrolyzable Schiff base groups (TFNAD) has been meticulously designed, synthesized, and copolymerized with commercial TFTPN and TTSBI, yielding a series of copolymers. Subsequently, in situ hydrolysis removes aniline from the membrane, freeing up the occupied free volume and creating additional channels for gas transport. This process substantially enhances gas permeability while preserving the desired selectivity. PIM-TFAD-30 showed a 68 % improvement in CO2 permeability with virtually no compromise in CO2/N2 selectivity compared to the pre-hydrolysis membrane. Meanwhile, PIM-TFAD-30 also displayed outstanding separation performance and plasticization resistance in simulated flue gas tests, demonstrating its potential for practical application. This facile and straightforward hydrolysis method opens up a new perspective for preparing and modifying polymeric separation membranes beyond gas separation.

Recycling mixed polymer particles using a spiral tube tribo‐electrostatic separation device

AbstractAt present, research on the electrostatic separation of polymers is primarily concentrated in the WEEE field, with limited studies addressing the electrostatic separation of vehicle polymers. In this study, tribo‐charging separation of PA66/PP (modified)/PE three‐component vehicle polymer mixed particles was investigated using a spiral tube tribo‐charged separation device. Firstly, a force model of particle movement in the spiral tube was established, and the theoretical analysis determined that the critical rotational speed of particle centrifugal movement is 70 rpm. Secondly, the optimal charging parameters were determined by single‐factor experiments and orthogonal experiments, and the effect of the blanking baffle on the particle charging was also investigated. Finally, high‐voltage electrostatic separation simulations and experiments were carried out, achieving separation purities of 92.8% for PA66, 80.7% for PP (modified), and 86.6% for PE, respectively. Results provide both theoretical and experimental reference for one‐pass electrostatic separation of three kinds of plastic particles by spiral tube turbo‐charged separation device.Highlights Separation of vehicle polymers is crucial for its high‐value‐added recycling. A spiral tube tribo‐electrostatic separation device is developed. The critical rotational speed of particle centrifugal movement is analyzed. The influence of the blanking baffle on the particle charge is investigated.

Stereoisomeric separation and chiral recognition mechanism study of star cyclodextrin polymer as the chiral stationary phase

BackgroundAs the derivatives of cyclodextrin (CD), cyclodextrin polymers (CDPs) effectively increase the concentration of CD units and construct supramolecular structures with unique stereoselectivity by the structure design. CDPs have shown significant potential in chiral separation, however, the process of stereoselective interactions on chiral stationary phases (CSPs) and the specific contribution of intermolecular forces are still a challenge issue. A comprehensive understanding of the chiral recognition mechanism of CDPs will help to optimize chiral separation conditions and design new CSPs. ResultsThe star CDP with a supermolecular structure was synthesized by grafting β-CD onto the external 6-position hydroxyl groups using β-CD as the parent nucleus. The enhanced host-guest recognition ability of CD supramolecular polymer structure provided better inclusion interaction and increased chiral recognition of the isomers. The Star-CD CSP with star CDP as a chiral ligand performed satisfactory stereoisomer separation ability with the separation factor (α) up to 2.0 for various quinoline alkaloid isomers and 1.89 for catechins. To elucidate its chiral separation mechanism, molecular docking was used to construct the three-dimensional visual models of the binding sites and the contribution of non-covalent interactions between Star-CD CSP and quinoline alkaloid isomers. In addition, the formation sites of non-covalent interactions on the CD monomers of the polymer side chains were confirmed from the actual geometric structure by analyzing the NMR chemical shift changes before and after the formation of complexes between Star-CD polymers and isomers. Combined with the mutual evidence of molecular simulation and chiral NMR, the specific recognition mechanism of selector-selectand complexes was comprehensively expounded. SignificanceThe multi-mode CSP based on cyclodextrin supramolecular structure provides new ideas for the stereoisomeric separation of complex chiral components with multiple chiral centers in natural products. Not limited to the macroscopic performance of the chromatographic separation, molecular docking explored the theoretical model of chiral recognition from the molecular level. The chiral NMR analysis confirmed the credibility of the model from the geometry structure, and then the recognition mechanism of multi-mode CSP was fully elaborated combining the above three aspects.

Migration and Separation of Polymers in Nonuniform Active Baths.

Polymerlike structures are ubiquitous in nature and synthetic materials. Their configurational and migration properties are often affected by crowded environments leading to nonthermal fluctuations. Here, we study an ideal Rouse chain in contact with a nonhomogeneous active bath, characterized by the presence of active self-propelled agents which exert time-correlated forces on the chain. By means of a coarse-graining procedure, we derive an effective evolution for the center of mass of the chain and show its tendency to migrate toward and preferentially localize in regions of high and low bath activity depending on the model parameters. In particular, we demonstrate that an active bath with nonuniform activity can be used to separate efficiently polymeric species with different lengths and/or connectivity.

Cross-Halbach magnetic levitation configuration for density-based measurement, separation and detection

Magnetic levitation (MagLev) is a well-documented and widely-applied technique in accurate, sensitive, and untethered testing of living and non-living materials in both macroscale and microscale. However, most magnetic levitation configurations face the dilemma between working range and sensitivity, since the distance between the two like-pole-facing magnets are in positive relationship with sensitivity, but negative with measuring range. And there exists a maximum distance for MagLev configurations where the misalignment happens when the distance is too large, which is a restriction on the working space and measurement range of the MagLev devices. In this paper, we propose a novel configuration based on the principle of Halbach array, namely the Cross-Halbach MagLev configuration. By doing parallel comparisons with the Standard MagLev consisting of magnets of the same size, we determined the superiority of the Cross-Halbach configuration in magnetic flux density (0.47 T) and B→∙∇B→z (6.25 T2/m), maximum distance (90 mm), sensitivity (525 mm/(g/cm3)) and wide linear zone on B→∙∇B→z (42 mm). To demonstrate and further explore the potential of the Cross-Halbach MagLev, we carried out a series of experiments, including density measurements of standard beads and different polymers, detection and separation of similar polymers with minute difference in density, and nondestructive detection of voids. The results indicate that the proposed magnetic levitation configuration is competent of density-based applications and can serve as a new solution to high-sensitivity measurement and detection.

Shape memory and mechanical properties of ESO modified epoxy/polyurethane semi-interpenetrating polymer networks for smart plaster

While numerous studies have explored the potential of shape memory materials in medical applications, the current research output is not enough for significant productivity in industrial products. In this research, a type of shape memory orthopedic plaster was fabricated by using epoxy/polyurethane interpenetrating networks modified with epoxidized soybean oil (ESO) and then compared with some commercial plasters. Polymer networks that were produced could be tailored to have glass transition temperatures (Tgs) within the range of 70–90 °C by changing the percentage composition of polyurethane and soybean oil. Shape recovery and fixity ratios in all samples were above 95 and 97 %. DMA results showed that IPNs with variable amount of soybean oil had lower glass transition temperature (Tg) and cross-link densities compared to IPNs without soybean oil. Based on the tensile test results, most samples exhibited an elastic modulus in the range of 280–400MPa, a level deemed somewhat acceptable when compared to commercial samples. Light microscope images had shown that the increase of polyurethane led to the phase separation of polymers, which was improved by the addition of soybean oil.

Tuning the Permeation Properties of Poly(1‐trimethylsilyl‐1‐propyne) by Vapor Phase Infiltration Using Trimethylaluminum

AbstractVapor phase infiltration (VPI) has emerged as a promising tool for fabrication of novel hybrid materials. In the field of polymeric gas separation membranes, a beneficial impact on stability and membrane performance is known for several polymers with differing functional groups. This study for the first time investigates VPI of trimethylaluminum (TMA) into poly(1‐trimethylsilyl‐1‐propyne) (PTMSP), featuring a carbon–carbon double bond as functional group. Saturation of the precursor inside the polymer is already attained after 60 s infiltration time leading to significant densification of the material. Depth profiling proves accumulation of aluminum in the polymer itself, but a significantly increased accumulation is visible in the gradient layer between polymer and SiO2 substrate. A reaction pathway is proposed and supplemented by density‐functional theory (DFT) calculations. Infrared spectra derived from both experiments and simulation support the presented reaction pathway. In terms of permeance, a favorable impact on selectivity is observed for infiltration times up to 1 s. Longer infiltration times yield greatly reduced permeance values close or even below the detection limit of the measurement device. The present results of this study set a strong basis for the application of VPI on polymers for gas‐barrier and membrane applications in the future.

Closed-Loop Recycling of Mixed Plastics of Polyester and CO2-Based Polycarbonate to a Single Monomer.

Physical blending is an effective strategy for tailoring polymeric materials to specific application requirements. However, physically blended mixed plastics waste adds additional barriers in mechanical or chemical recycling. This difficulty arises from the intricate requirement for meticulous sorting and separation of the various polymers in the inherent incompatibility of mixed polymers during recycling. To overcome this impediment, this work furthers the emerging single-monomer - multiple-materials approach through the design of a bifunctional monomer that can not only orthogonally polymerize into two different types of polymers - specifically lactone-based polyester and CO2-based polycarbonate - but the resultant polymers and their mixture can also be depolymerized back to the single, original monomer when facilitated by catalysis. Specifically, the lactone/epoxide hybrid bifunctional monomer (BiLO) undergoes ring-opening polymerization through the lactone manifold to produce polyester, PE(BiLO), and is also applied to ring-opening copolymerization with CO2, via the epoxide manifold, to yield polycarbonate, PC(BiLO). Remarkably, a one-pot recycling process of a BiLO-derived PE/PC blend back to the constituent monomer BiLO in >99 % selectivity was achieved with a superbase catalyst at 150 °C, thereby effectively obviating the requirement for sorting and separation typically required for recycling of mixed polymers.

Closed‐Loop Recycling of Mixed Plastics of Polyester and CO2‐Based Polycarbonate to a Single Monomer

AbstractPhysical blending is an effective strategy for tailoring polymeric materials to specific application requirements. However, physically blended mixed plastics waste adds additional barriers in mechanical or chemical recycling. This difficulty arises from the intricate requirement for meticulous sorting and separation of the various polymers in the inherent incompatibility of mixed polymers during recycling. To overcome this impediment, this work furthers the emerging single‐monomer – multiple‐materials approach through the design of a bifunctional monomer that can not only orthogonally polymerize into two different types of polymers – specifically lactone‐based polyester and CO2‐based polycarbonate – but the resultant polymers and their mixture can also be depolymerized back to the single, original monomer when facilitated by catalysis. Specifically, the lactone/epoxide hybrid bifunctional monomer (BiLO) undergoes ring‐opening polymerization through the lactone manifold to produce polyester, PE(BiLO), and is also applied to ring‐opening copolymerization with CO2, via the epoxide manifold, to yield polycarbonate, PC(BiLO). Remarkably, a one‐pot recycling process of a BiLO‐derived PE/PC blend back to the constituent monomer BiLO in >99 % selectivity was achieved with a superbase catalyst at 150 °C, thereby effectively obviating the requirement for sorting and separation typically required for recycling of mixed polymers.

Versatile room temperature phosphorescence polymer with luminophore content as low as 0.05 wt%

To impart processability and practical serviceability to organic room temperature phosphorescence (RTP) molecules, and address phase separation and rigid confinement environment of conventional RTP polymers, a small amount of Schiff base bonds crosslinked tetraphenylene luminescence networks are pinned to the borate ester bonds crosslinked epoxy networks producing reversible interlocked polymer networks-based halogen-free RTP material. By taking advantage of the conjugation interaction of Schiff base linkages, and phase separation inhibition/molecular confinement effects of the interlocking networks, excellent fluorescence quantum yield (up to 78.9 %), RTP lifetime (660 ms) and quantum yield (16.7 %) are achieved with ultra-low concentration of luminophores (0.05 wt%). Moreover, the resultant acquires decent tensile strength (3.8 MPa) and a high elongation-at-break (365 %) owing to its unique molecular design. The phosphorescence lifetimes (457 ∼ 602 ms) are only slightly affected even after cyclic stretching (at 50 % strain for 100 cycles), or soaking in water (for 30 days), or heating (90 °C). The built-in reversible covalent bonds and the topological network reorganization further enable injection molding and self-healing of the material. Having been repeatedly crushed/hot-pressed, the recycled material still shows RTP lifetime and quantum yield of 398 ms and 14.6 %, respectively. The present work provides a feasible approach to fabricate multifunctional robust organic phosphorescent materials with application prospects.

Superior polymeric gas separation membrane designed by explainable graph machine learning

Superior polymeric gas separation membrane designed by explainable graph machine learning

Bio-inspired superhydrophobic fiber membrane for oil-water separation and non-destructive transport of liquids in corrosive environments

Conventional polymer separation membranes or coatings suffer from poor separation performance and serious failure in highly corrosive environments, due to their low chemical and mechanical stability. Herein, a simple electrospraying and electrospinning strategy was used to prepare flexible superhydrophobic carbon fiber membranes (FSCFM). The wettability of FSCFM was improved by forming a lotus leaf-like hierarchical rough structure on its surface. The FSCFM exhibited an excellent permeation flux of immiscible oil-water mixtures (up to 15,800 L m−2 h−1) and water-in-oil emulsions (over 5500 L m−2 h−1), while the separation efficiencies were always kept at more than 99 % after 25 consecutive separations. Even in corrosive environments, its separation performance did not show any degradation. Notably, except for recovering floating oil under external driving forces with excellent cyclic stabilities, FSCFM was also able to transport various corrosive solutions with high efficiencies (99.9 %). After multiple mechanical damages and bending cycles, the FSCFM remained superhydrophobic. It could also maintain its repellency in strong acids/bases, high salt solutions and even under high-temperature environments (94.5 °C). These superior properties make it a strong candidate for oil-water mixture/emulsion separation and non-destructive transport of highly corrosive fluids.

Fabrication of Crescent Shaped Microparticles for Particle Templated Droplet Formation.

Crescent-shaped hydrogel microparticles are shown to template uniform volume aqueous droplets upon simple mixing with aqueous and oil media for various bioassays. This emerging "lab on a particle" technique requires hydrogel particles with tunable material properties and dimensions. The crescent shape of the particles is attained by aqueous two-phase separation of polymers followed by photopolymerization of the curable precursor. In this work, the phase separation of poly(ethylene glycol) diacrylate (PEGDA, Mw 700) and dextran (Mw 40000) for tunable manufacturing of crescent-shaped particles is investigated. The particles' morphology is precisely tuned by following a phase diagram, varying the UV intensity, and adjusting the flow rates of various streams. The fabricated particles with variable dimensionsencapsulate uniform aqueous droplets upon mixing with an oil phase. The particles are fluorescently labeled with red and blue emitting dyes at variable concentrations to produce six color-coded particles. The blue fluorescent dye shows a moderate response to the pH change. The fluorescently labeled particles are able to tolerate an extremely acidic solution (pH 1) but disintegrate within an extremely basic solution (pH 14). The particle-templated droplets are able to effectively retain the disintegrating particle and the fluorescent signal at pH 14.

Polynorbornenes with carbocyclic substituents: A perspective approach to highly permeable gas separation membranes

Gas transport properties of two sets of polynorbornenes bearing carbocyclic substituents of different nature (cyclohexyl, norbornyl, phenyl groups, and framed oligocyclic moieties) were systematically studied. The influence of side chain carbocyclic substituents on gas permeability and separation selectivity for CO2-containing gas pairs and gaseous hydrocarbons was evaluated. It was found that the presence of carbocyclic moieties in side chains of polynorbornenes promotes the increase in gas permeability similarly to that of SiMe3 groups, with this effect being enhanced by the increase in the number of cycles in the substituents. As a result, P(CO2) of the metathesis polymer with pentacene-based substituents is equal to 1200 Barrer. Studied polynorbornenes with carbocyclic substituents displayed promising gas separation selectivities: CO2/N2 separation selectivity up to 41 (above the 2008 upper bound in the Robeson diagram) and solubility-controlled hydrocarbon separation selectivity up to 16 for the n-butane/methane gas pair. For the polymer with pentacene-based substituents, the separation of the mixture of hydrocarbons and aging were studied. The studies revealed that the mixed gas C4/C1 separation selectivity of this polymer reaches 4, and a two-time reduction of permeability occurs in 8.5 months. Therefore, the incorporation of carbocyclic groups in the side chains of polynorbornenes can be considered as an efficient strategy for the design of polymeric gas separation membrane materials.

Domain of influence on generalized thermoelastic diffusion theory

The aim of this research work is to establish the theory of the domain of influence of diffusion disturbance with potential-temperature disturbance under the theory of generalized thermo-elastic diffusion using Lord and Shulman model. For a finite time t > 0, it has been proved that the potential due to displacement, temperature and diffusion effect does not produce any disturbances outside a bounded domain and the domain of influence is dependent on the support of thermo-elasto-diffusive load, the thermo-elasto-diffusive coupling constant and the phase-lag parameters. It has been shown that the domain of influence of the present case reduce to the domain of influence for classical thermo-elasticity theory with or without diffusion and the thermo-elasticity theory with one relaxation parameter without diffusion. Also, the effect of diffusion on thermal wave propagation is shown. This theorem will be applicable to analyze the deformation occur in elastic solids due to internal and external loads for the thermo-elasto-diffusive models and problems based on it in the field of engineering physics like solid-state-physics, physical metallurgy (fabrication of semi-conductor devices in mixture metals and molten semi-conductor), material engineering (separation of polymers), aircraft engineering, mechanical engineering and also in the industries like oil extraction from hydrocarbon and manipulation of macro-molecules like DNA etc.

Inside Cover Picture

Triphenylamine and its derivatives (TPAs) are promising for the photocatalytic oxidative coupling of thiols to disulfides, but suffer from the easy polymerization and difficult separation. In this paper, by immobilizing the TPAs into MOF with photoredox inert Sr nodes, the photo‐generated electrons were successfully controlled to transfer from the excited TPAs to O2, and finally realize the heterogeneous catalytic oxidation of thiols to disulfides. More details are discussed in the article by Zhang et al. on page 1093—1099.image

Vapor-induced phase-separation-enabled versatile direct ink writing

Versatile printing of polymers, metals, and composites always calls for simple, economic approaches. Here we present an approach to three-dimensional (3D) printing of polymeric, metallic, and composite materials at room conditions, based on the polymeric vapor-induced phase separation (VIPS) process. During VIPS 3D printing (VIPS-3DP), a dissolved polymer-based ink is deposited in an environment where nebulized non-solvent is present, inducing the low-volatility solvent to be extracted from the filament in a controllable manner due to its higher chemical affinity with the non-solvent used. The polymeric phase is hardened in situ as a result of the induced phase separation process. The low volatility of the solvent enables its reclamation after the printing process, significantly reducing its environmental footprint. We first demonstrate the use of VIPS-3DP for polymer printing, showcasing its potential in printing intricate structures. We further extend VIPS-3DP to the deposition of polymer-based metallic inks or composite powder-laden polymeric inks, which become metallic parts or composites after a thermal cycle is applied. Furthermore, spatially tunable porous structures and functionally graded parts are printed by using the printing path to set the inter-filament porosity as well as an inorganic space-holder as an intra-filament porogen.