Polyether Block Research Articles

Dha Tab-COF filled PEBAX mixed matrix membranes for effective CO2/CH4 separation

Covalent organic skeletons (COFs) have been widely used in gas separation due to their excellent pore structure, high crystallinity, and high specific surface area. In this work, Dha Tab-COF was synthesized by solvothermal method and filled in polyether block polyamide (PEBAX) to form mixed matrix membranes (MMMs). Various characterization methods such as Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were used to characterize the structure of Dha Tab-COF as well as the MMMs. The effects of operating pressure, operating temperature and the content of Dha Tab-COF particles on the CO2/CH4 separation performance of the membranes were investigated. The best separation performance with a CO2 permeability of 295.8 Barrer and a CO2/CH4 selectivity of 21.6 was achieved when the Dha Tab-COF content is 2 wt%, which were 45.7% and 108.1% higher than that of the pure PEBAX membrane, respectively.

Low-Velocity Impact Resistance and Compression After Impact Strength of Thermoplastic Nanofiber Toughened Carbon/Epoxy Composites with Different Layups.

This study investigates the effectiveness of polyether block amide (PEBA) thermoplastic elastomeric nanofibers in reducing low-velocity impact damage across three carbon fiber composite lay-up configurations: a cross-ply [0°/90°]2s (CP) and a quasi-isotropic [0°/45°/90°/-45°]s (QI) lay-up utilizing unidirectional plies, and a stacked woven [(0°,90°)]4s (W) lay-up using twill woven fabric plies. The flexural strength and interlaminar shear strength of the composites remained unaffected by the addition of nanofibers: around 750 MPa and 63 MPa for CP, 550 MPa and 58 MPa for QI, and 650 MPa and 50 MPa for W, respectively. The incorporation of nanofibers in the interlaminar regions resulted in a substantial reduction in projected damage area, ranging from 30% to 50% reduction over an impact energy range of 5-20 J. Microscopic analysis showed that especially the delamination damage decreased in toughened composites, while intralaminar damage remained similar for the cross-ply and quasi-isotropic lay-ups and decreased only in the woven lay-up. This agrees with the broad body of research that shows that interleaved nanofibers result in a higher delamination resistance due to toughening mechanisms related to nanofiber bridging of cracks. Despite their ability to mitigate delamination during impact, nanofibers showed limited positive effects on Compression After Impact (CAI) strength in quasi-isotropic and cross-ply composites. Interestingly, only the woven fabric composites demonstrated improved CAI strength, with a 12% improvement on average over the impact energy range, attributed to a reduction in both interlaminar and intralaminar damage. This study indicates the critical role of fiber integrity over delamination size in determining CAI performance, suggesting that the delaminations are not sufficiently large to induce buckling of sub-layers, thereby minimizing the effect of nanofiber toughening on the CAI strength.

Synthesis of Polyether Block Copolymers from 1,2-Epoxybutane and AEOn and Comparative Study of Physicochemical and Application Properties before and after the Synthesis.

In this study, the AEOnBO2 series of block polyoxybutenol ethers was synthesized by combining the AEO series of polyoxyethylene and preparing 1,2-epoxybutane (BO) block polyether using a semicontinuous method. The synthesis was performed by HPLC, MALDI-TOF-MS, FT-IR, and 1H NMR for structural analysis. The interaction parameters and surface tension of the systems before and after synthesis were studied using surface tension meter. The diffusion process of the systems before and after synthesis was studied using a KRÜSS bubble pressure tensiometer. The surfactant properties of AEOn and AEOnBO2 were evaluated by static and dynamic surface tension measurements. Each system formed a saturated adsorption layer in a water solution. The critical micelle concentration decreased dramatically after the introduction of BO groups, and the diffusion-adsorption process was consistent with the kinetic mechanism of hybrid diffusion. The microscopic self-assembled aggregate micellar behavior of all the systems was investigated using DLS, TEM, and SEM. The micellization process in all systems was spontaneous and enthalpy-driven, forming spherical aggregates, with the BO block reducing the aggregate diameter of the feedstock from 220.06 nm to about one-third of 80.02 nm. In addition, the dynamic contact angle, application, and physicochemical properties such as foaming and foam stabilization of each system were investigated. The contact angle was reduced from 70 to 50° at 120 s of stabilization, with a foam volume of 80 mL in all systems at 200 s. However, the AEOnBO2 showed accelerated foam decay at 500 s, with an increase in the contact angle from 70 to 50° at 200 s, but the AEOnBO2 showed accelerated foam decay at 500 s, with a decrease in the contact angle from 70 to 50° at 120 s stabilization. At 200 s, the foam volume of all systems was 80 mL, but AEOnBO2 showed an accelerated foam decay process, which shows that the BO group can accelerate the foam decay, and the comparative results show that the BO group can also optimize other application properties and physicochemical properties.

Synthesis and properties of carboxyl-modified polyether block silicone surfactants

Synthesis and properties of carboxyl-modified polyether block silicone surfactants

Building high-speed facilitated transport channels in Pebax membranes with montmorillonite for efficient CO2/N2 separation

ABSTRACT Development of high-performance mixed matrix membranes (MMMs) is of great significance for CO2 separation membrane technology, in order to improve the commercial competitiveness and practical applications. Montmorillonite (MMT) was developed as a dopant to fabricate Polyether block amide (Pebax1074)-based MMMs for strengthening the CO2/N2 separation. The morphology, chemical groups, microstructure, and thermal properties of MMMs were characterised by scanning electron microscope, FTIR spectroscopy, X-ray diffraction and thermal analysis, respectively. The effects of MMT contents, permeation pressure and permeation temperature on the gas separation performance of the Pebax/MMT MMMs were investigated. The results show that the uniformly dispersed dopants MMT in the membrane matrix significantly influence the thermal stability and the structural compactness of MMMs. Moreover, the CO2 permeability monotonously increases in spite of the CO2/N2 selectivity first increasing and then decreasing with the MMT content elevating from 0% to 10% in MMMs. The highest CO2/N2 selectivity could reach to 120.3, along with the CO2 permeability of 130.6 Barrer for the MMMs made by MMT content of 6%.

Cell Structure Variation of Long-Chain Branched Polyether Block Amide Regulated by Crystallization Behavior

Cell Structure Variation of Long-Chain Branched Polyether Block Amide Regulated by Crystallization Behavior

Reinforced facilitated transport PEBA membrane by 2D Fe-doped TiO2 macroporous nanosheets for CO2 separation: Utilizing cationic and non-ionic surfactants

In this study, macroporous nanosheets of 2D Fe-Doped TiO2 were synthesized, and subsequently, membranes composed of polyether block amide (PEBA) were prepared. These membranes were incorporated with the nanosheets mentioned above, as well as two distinct types of surfactant. The structure and gas separation properties of the membranes were studied using different methods, including atomic force microscopy (AFM), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), as well as gas permeation analyses and tensile test. The findings indicated that the nanosheets underwent a porous transformation following the doping process. This occurrence improved the bonding between the nanosheets and PEBA chains, consequently boosting the mechanical strength of the membranes embedded with these nanosheets. Incorporating these nanosheets into the membrane (4 wt%) established a more efficient facilitated transport mechanism via Lewis acid centers, resulting in a 12.5 % increase in CO2 permeability and a 136 % rise in the selectivity of CO2/N2 compared to the pure PEBA membrane. Two different surfactants were introduced to the PEBA/FeTiO2 matrix, resulting in varying impacts on membrane structure and performance. The Cetyl trimethyl ammonium bromide (CTAB) as a cationic surfactant led to membrane stiffening and a significant 241 % enhancement in CO2/N2 selectivity at 1 wt%. On the other hand, the Polysorbat (Tween) as a non-ionic surfactant softened the membrane and boosted CO2 permeability by 53 % at 6 wt% compared to the pure membrane.

Prompt gamma activation analysis for boron determination in the tens of milligram range at the HOTNES facility

Boron is an elective element for the Prompt Gamma Activation Analysis (PGAA), due to its exceptionally large neutron capture cross section. This technique, usually performed in nuclear reactors with neutron fluxes as high as 108 cm−2 s−1, can determine quantities of boron as low as tens of nanograms. Some applications, such as the industry of neutron shielding materials, would better benefit from a less sensitive but more portable and accessible boron PGAA, which could be established at construction or fabrication sites. For these purposes ENEA and INFN jointly setup a compact PGAA based on a 0.5 cm3 Cadmium–Zinc–Telluride gamma spectrometer and the HOTNES thermal neutron source. Relying on a series of borated resins with known composition and on comprehensive experimental and Monte Carlo evaluations, this technique features a detection limit in the order of few milligrams in terms of boron mass. As the facility consists simply on a lab-scale neutron source and a polyethylene block with well-established geometry, this simplified PGAA system is suited to be replicated or transported to construction or fabrication sites for QA/QC purposes on borated construction materials for the nuclear sector.

Enhancement of CO2 separation efficiency in mixed matrix membranes through zinc ion modified g‐C3N4 nanosheets

AbstractThis study employed modified graphitic carbon nitride (g‐C3N4) nanosheets and polyether block amide (Pebax) to prepare mixed matrix membranes (MMMs) aiming to enhance CO2 separation efficiency. Through sulfonation and zinc ion (Zn2+) modification of g‐C3N4 nanosheets, high Zn2+ loaded nanofillers (SCN‐Zn2+) were synthesized. Compared to g‐C3N4, MMMs with SCN‐Zn2+ as nanofiller showed a CO2 permeance of 462 Barrer as well as the CO2/N2 selectivity of 47.5 at the feed gas pressure of 2 bar, which surpassed the 2008 Robeson upper bound. Additionally, the Pebax/SCN‐Zn2+(30) membrane was subjected to continuous gas permeability experiments for 70 h and showed good stability. The results showed that SCN‐Zn2+ nanosheets played an important role in enhancing the gas selectivity of the membranes. SEM confirmed that the SCN‐Zn2+ nanosheets had good compatibility with the Pebax substrate and the presence of hydrophilic sulfonic acid groups effectively suppressed the interfacial defects. The increase in the free volume fraction of the membranes as well as the solubility and diffusion coefficient suggested that the introduction of g‐C3N4 nanosheets led to more tortuous gas transport paths, which enhanced the permeability and selectivity of CO2.

Measurement of effective 98Mo(n,γ)99 Mo reaction cross-section in the epi-cadmium neutron flux produced by 10 MeV electron LINAC with Ta-BeO assembly

An experiment was carried out to study the feasibility of 99Mo production using an electron accelerator based epi-cadmium neutron source. The neutrons were produced by the interaction of bremsstrahlung end-point energy of 10 MeV with BeO blocks and the neutrons thus produced were moderated using High Density Polyethylene blocks. Effective cross-section of 98Mo(n,γ)99Mo reaction was measured using foil activation method. An enhancement in the effective cross-section due to resonances in the epi-cadmium region was observed. The photons and neutron production/transport in the experimental set-up were simulated using the FLUKA Monte Carlo code. The simulations were found to be in good agreement with the experimental findings.

Effect of Insertional Direction of Pedicle Screw on Screw Loosening: A Biomechanical Study on Synthetic Bone Vertebra under a Physiology-like Load.

It is now understood that pedicle screw loosening at the implant-bone interface can lead to poor screw-bone interface purchase and decreased fixation stability. Previous biomechanical tests used cadaveric vertebrae and pull-out or torque loads to assess the effect of the insertional direction of pedicle screws on screw loosening. However, these tests faced challenges in matching biomechanical differences among specimens and simulating in vivo loads applied on pedicle screws. This study aimed to evaluate the effect of the insertional direction of pedicle screws on screw loosening using tension-compression-bending loads and synthetic bone vertebrae. Polyaxial pedicle screws were inserted into nine synthetic bone vertebrae in three directions (three samples per group): cranial, parallel, and caudad (-10°, 0°, +10° of the pedicle screw rod to the upper plane of the vertebra, respectively). Pedicle screws in the vertebrae were loaded using a polyethylene block connected to a material testing machine. Tension-compression-bending loads (100N-250N) with 30,000 cycles were applied to the pedicle screws, and displacements were recorded and then cycle-displacement curve was drawn based on cycle number. Micro-CT scans were performed on the vertebrae after removing the pedicle screws to obtain images of the screw hole, and the screw hole volume was measured using imaging analysis software. Direct comparison of displacements was conducted via cycle-displacement curve. Screw hole volume was analyzed using analysis of variance. The correlation between the displacement, screw hole volume and the direction of pedicle screw was assessed by Spearman correlation analysis. The smallest displacements were observed in the caudad group, followed by the parallel and cranial groups. The caudad group had the smallest screw hole volume (p < 0.001 and p = 0.009 compared to the cranial and parallel groups, respectively), while the volume in the parallel group was greater than that in the cranial group (p = 0.003). Correlation analysis revealed that the insertional direction of the pedicle screw was associated with the displacement (p = -0.949, p < 0.001) and screw hole volume (p = -0.944, p < 0.001). Strong correlations were found between the insertional direction of the pedicle screw and relevant parameters, including displacement and screw hole volume. Pedicle screw insertion in the caudad direction resulted in the least pedicle screw loosening.

Increasing the Permeability of Carbon Dioxide and Nitrogen Gases Through a Polymer Membrane Consisting of a Modified Polyether Block Amide and Experimental Design

Increasing the Permeability of Carbon Dioxide and Nitrogen Gases Through a Polymer Membrane Consisting of a Modified Polyether Block Amide and Experimental Design

Flexible PLA Copolymers with Low Melt Flow Index for Blown Film Applications

AbstractA series of strategies are investigated, which allow internally plasticized polylactide (PLA)‐polyether block copolymers to be effectively melt‐processed through blown film extrusion in the semi‐technical scale. Among the strategies presented are the use of tris(nonylphenyl) phosphite (TNPP) as a chain extender during the ring opening polymerization (ROP) of lactide and the application of ε‐caprolactone (CL) as a plasticizing comonomer. The produced films have a significantly higher flexibility than pure PLA films and are in a comparable range to the flexibility of fossil‐based, film‐grade low‐density polyethylene (LDPE) films.

Green electrospun Janus membrane of polyether block amide (PEBA) doped with hierarchical magnesium hydrogen phosphate for the removal of pharmaceuticals and personal care products

It has been a challenge to prepared polyether block amide (PEBA) fibrous membrane via solution electrospinning. The only few reported methods though involved hazardous solvents and surfactants which were against the principle of green chemistry. In this work, uniform fibrous membrane of PEBA was successfully fabricated by solution electrospinning with a bio-based solvent dihydrolevoglucosenone (Cyrene). To further improve the mechanical strength and adsorption performance of the PEBA membrane, a hierarchical magnesium hydrogen phosphate (MgHPO4·1.2H2O, MHP) was synthesized to blend evenly into the PEBA matrix. A Janus MHP/PEBA membrane with one side of hydrophobic surface and the other side of hydrophilic surface was subsequently prepared, which exhibited fast adsorption, high capacity, good selectivity and reusability towards ibuprofen, acetaminophen, carbamazepine and triclosan. In addition, the Janus membrane showed high removal efficiency of the above contaminants in secondary wastewater effluent with good long term stability. It demonstrated that this Janus MHP/PEBA membrane had a good potential in practical wastewater treatment.

CO2-Philic Nanocomposite Polymer Matrix Incorporated with MXene Nanosheets for Ultraefficient CO2 Capture.

The incorporation of two-dimensional (2D) functional nanosheets in polymeric membranes is a promising material strategy to overcome their inherent performance trade-off behavior. Herein, we report a novel nanocomposite membrane design by incorporating MXene, a 2D sheet-like nanoarchitecture known for its advantageous lamellar morphology and surface functionalities, into a cross-linked polyether block amide (Pebax)/poly(ethylene glycol) methyl ether acrylate (PEGMEA) blend matrix, which delivered exceptional CO2/N2 and CO2/H2 separation performances that are critical to industrial CO2 capture applications. The finely dispersed Ti3C2Tx nanosheets in the blend polymer matrix led to an expansion of the free volume within the resultant mixed matrix membrane (MMM), giving rise to a substantially enhanced CO2 permeability of up to 1264.6 barrer, which is 102% higher than that of the pristine polymer. Moreover, these MXene-incorporated MMMs exhibited preferential sorption for CO2 over light gases, which contributed to an exceptional CO2/N2 and CO2/H2 selectivity (64.3 and 19.2, respectively) even at a small loading of only 1 wt %, allowing the overall performance to not only surpass the latest upper bounds but also exceed many previously reported high-performance nanosheet-based nanocomposite membranes. Long-term performance tests have also demonstrated the good stability of these membranes. This composite membrane design strategy reveals the remarkable potential of combining a blend copolymer matrix with ultrathin MXene nanosheets to achieve superior gas separation performance for environmentally important gas separations.

Design and Usability of an Open-Source, Low-Cost Flexible Laryngoscope for Resource-Limited Settings

Endoscopes are paramount to the practice of otolaryngology. To provide physicians in low-middle-income countries with adequate tools to treat otolaryngologic problems, it is necessary to create a low-cost sustainable option. To describe the design and usability of an open-source, low-cost flexible laryngoscope that addresses the lack of affordable and accessible methods for otolaryngologic visualization in resource-limited settings. This quality improvement study used a mixed-methods approach, including a technical description of device design as well as quantitative and qualitative survey evaluation of device usability. Engineering involved device design, sourcing or manufacturing individual components, fabricating a prototype, and iterative testing. Key assumptions and needs for the device were identified in collaboration with otolaryngologists in Zimbabwe, and designed and simulated by biomedical engineers in a US university laboratory. Board-certified otolaryngologists at a single US university hospital trialed a completed prototype on simulated airways between May 2023 and June 2023. Technical details on the design of the device are provided. Otolaryngologist gave feedback on device characteristics, maneuverability, and visualization using the System Usability Scale, a customized Likert-scale questionnaire (5-point scale), and semistructured interviews. A functional prototype meeting requirements was completed consisting of a distal-chip camera, spring bending tip, handle housing the control mechanism and electronics, and flexible polyether block amide-coated silicone sheath housing the camera and control wires; an external monitor provided real-time visualization and ability to store data. A total of 14 otolaryngologists participated in the device review. The mean (SD) System Usability Scale score was 88.93 (10.08), suggesting excellent usability. The device was rated highly for ease of set up, physical attributes, image quality, and functionality. This quality improvement study described the design of a novel open-source low-cost flexible laryngoscope that external review with otolaryngologists suggests was usable and feasible in various resource-limited environments. Future work is needed to translate the model into a clinical setting.

Morphology and confinement effects on crystallization kinetics in polyethylene containing block copolymers

This paper investigates the morphology and crystallization kinetics of polyethylene (PE) containing block copolymers, differing in block number (di- vs. triblock copolymers) and composition (ABA triblock co- vs. ABC triblock terpolymers). In these block copolymers, the crystallizable PE block is linked to amorphous poly(methyl methacrylate) (PMMA) and/or polystyrene (PS) blocks, and for one triblock terpolymer, poly(ethylene oxide) (PEO) was introduced as an additional crystallizable block. The topological confinement exerted by the covalent linkage of PE to the other blocks (glassy PMMA and PS, PEO) in combination with the morphological confinement into different PE microdomains (cylinders, lamella) significantly influence the crystallization behavior, resulting in slower crystallization kinetics compared to pure PE. The strongest effects were observed for triblock terpolymers, where the lamellar PE domains are disrupted by PS cylinders or distorted PS domains. This research enhances our understanding of block copolymers with confined crystallizable segments, aiding in tailored material design.

Super‐Elastic and Dimensionally Stable Polyether Block Amide Foams Fabricated by Microcellular Foaming with CO2&amp;N2 as Co‐Blowing Agents

AbstractPolyether block amide (PEBA) is an important thermoplastic polyester elastomer (TPE) owing to its low density and high resilience. Microcellular foaming can endow PEBA with significant potential in sports, medical, and industrial applications. However, with the current microcellular foaming technology, it remains challenging to obtain PEBA foams with stable shapes, which are critical for their mechanical properties. Therefore, microcellular foaming with CO2 and N2 as co‐blowing agents is utilized in this study to achieve mechanically robust PEBA foams by reducing the dimensional shrinkage. The introduction of N2 can effectively slow the diffusion rate of blowing agents into the air, providing support for the foam to resist external atmospheric pressure and effectively reducing the dimensional shrinkage of PEBA foams. Consequently, a stable foam shape is achieved with an expansion ratio of 7.9. Finally, the PEBA foams with excellent shrinkage resistance and mechanical properties are prepared, and the cell shrinkage mechanism is analyzed to study the effects of blowing agents and foaming methods on the structural evolution of TPE foams. This promising outcome paves way for their practical industrial applications.

Boosting pervaporation performance of polyether block amide membranes by embedding structural-evolution zeolitic imidazolate framework-71s for phenol/water separation

Given the increasing concerns for both the environment and human health, the treatment of wastewater containing phenolics has emerged as a pressing yet daunting matter. In this work, the mixed matrix membranes (MMMs) with exceptional performance have been created by introducing controllable morphology and structure zeolitic imidazolate framework-71s (ZIF-71s) into polyether block amide (PEBA) matrix for the purpose of phenol-water separation. The impacts of ZIF-71s dimension and ZIF-71s loading amount on the separation performance were comprehensively analyzed, as well as operational temperature and operational concentration on the separation performance. The crystal transformation of three-dimensional ZIF-71K nanoparticles into two-dimensional ZIF-71P nanosheets was accomplished by altering the modulators in aqueous system. The presence of ZIF-71s could lead to a decrease in water flux, while the phenol permeation flux was essentially unaffected. The filling of two-dimensional ZIF-71P nanosheets established a classic “brick-and-mortar” structure within the polymeric bulk, which resulted in the enhancement of tortuous pathways and energy barriers for water penetration, hence further boosted the membrane selectivity. For an operating temperature of 50 °C and a phenol concentration of 1000 ppm, the ZIF-71P/PEBA-21 MMMs exhibited separation performance with total permeate flux and separation factor of 911.10 g·m−2·h−1 and 18.96, while the ZIF-71K/PEBA-21 membrane demonstrated total permeate flux and separation factor of 965.49 g·m−2·h−1 and 17.74. And the MMMs presented a superior separation performance in comparison with the PEBA/PVDF membrane. On top of that, the resultant MMMs also demonstrated promising long-term stability as phenol enrichment methods, which holds significant promise for implementation in the recovery of phenol from relevant industrial wastewater.

Design of Neutron Activation and Radiography Facilities Based on DD Generator

Design and simulation of radiation facility using deuterium-deuterium (DD) neutron generator for neutron activation analysis (NAA) and radiography have been conducted by PHITS 3.30. A cylindrical DD neutron tube (E = 2.45 MeV isotropic, 5 x 109/s) flux is surrounded by high-density polyethylene blocks which serve as the moderator. Within the moderator there are several cavities to perform neutron activation experiments. A 90 cm long beam tube is installed either radially or tangentially for radiography purposes. Monte Carlo simulations then calculate the thermal flux inside the cavities and on the end of the beam tube. The biggest thermal flux obtained in the activation chambers is about 1.95 x 109/(cm2.s) in the cavity closest to the source center. Radial beam tube delivers thermal flux of 7.86 x 103/(cm2.s), while tangential beam tube transports 1.86 x 103/(cm2.s). Although the thermal flux in the radial beam tube is higher, the fast neutron flux is also higher, about 9.60 x 103/(cm2.s). Tangential beam tube configuration can decrease fast neutron flux to only 2.00 x 102/(cm2.s). This result can serve as a preliminary study for the commisioning of radiation facilities based on compact, low-power neutron source.