Polyacrylonitrile/Crown Ether Composite Nanofibres With High Efficiency for Adsorbing Li(I): Experiments and Theoretical Calculations

Lithium, as the lightest alkali metal, is widely used in military and new energy applications. With the rapid growth in demand for lithium resources, it has become necessary to improve the effectiveness of extraction thereof. By using chemical grafting and electrospinning techniques, nanofibres containing crown ether were developed for adsorbing Li(I) from the brine in salt lakes, so as to selectively adsorb Li(I) on the premise of retaining specific vacancies of epoxy groups in crown ether. In lithium-containing solution, the adsorbing materials can reach adsorption equilibrium within three hours, and the maximum adsorption capacity is 4.8 mg g−1. The adsorption mechanisms of the adsorbing materials for Li(I) were revealed by combining Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) with density functional theory (DFT) calculation. The results indicated that in crown ether, O in epoxy groups was coordinated with Li(I) to form Li–O and four O atoms in the epoxy groups were used as electron donors. After coordination, two O atoms protruded from the plane and formed a tetrahedral structure with Li(I), realising the specific capture of Li(I). By desorbing fibres that adsorbed Li(I) with 0.5-M HCl, the adsorption capacity only decreased by 10.4% after five cycles, proving ability to regenerate such materials. The nanofibres containing crown ether synthesised by chemical grafting and electrospinning have the potential to be used in extracting lithium resources from the brine in salt lakes.

The influence of silane on the physico-mechanical properties of vulcanizates using bentonite fillers

Layered phyllosilicate fillers have received attention in the polymer industry due to their unique nanoscale sheet-like structure. Adding a small amount of bentonite nanofiller gives rise to improved mechanical, thermal, and gas barrier properties of rubber mixtures. Depending on the application, natural bentonite is often modified by physical processes or by chemical processes (intercalation, cation exchange process, functionalization, pillaring, etc.). Chemical modification increases the size of the interlayer spaces and provides a hydrophobic environment. Functionalization (e.g., silanization), which encompasses the chemical grafting of thermally stable silane coupling agents onto the clay platelets, make inorganic bentonite and the organic polymer matrix compatible. In the introduced study, commercial bentonite P130 from Lieskovec deposit was modified by silane (3-aminopropyl trietoxysilane) treatment. Different techniques such as infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize modified and raw bentonite sample. Silanized P130s and raw product P130 were added to the natural rubber matrix to examine the influence of chemically functionalized bentonite on curing characteristic (M H, M L, t s2, t 90, ΔM) and mechanical properties (TSb, Eb, hardness) of rubber vulcanizates. Organo-bentonite was mixed into a rubber blend in particular ratio of 5, 10, 15, 20 phr in various combination with silane (3-aminopropyl triethoxysilane), Perkasil and carbon black. The highest maximum torque values were obtained with the sample using 20 phr of silanized P130s. The tensile strength (TSb) values decreased with increasing P130 content, as well as non-silanized and silanized P130. However, when 20 phr P130s was used, value of TSb was higher. The most enhanced properties of rubber blends were found with the addition of 20 phr of silanized bentonite P130s.

Partial Polymer Blend for Fused Filament Fabrication with High Thermal Stability

The materials for large scale fused filament fabrication (FFF) are not yet designed to resist thermal degradation. This research presents a novel polymer blend of polylactic acid with polypropylene for FFF, purposefully designed with minimum feasible chemical grafting and overwhelming physical interlocking to sustain thermal degradation. Multi-level general full factorial ANOVA is performed for the analysis of thermal effects. The statistical results are further investigated and validated using different thermo-chemical and visual techniques. For example, Fourier transform infrared spectroscopy (FTIR) analyzes the effects of blending and degradation on intermolecular interactions. Differential scanning calorimetry (DSC) investigates the nature of blending (grafting or interlocking) and effects of degradation on thermal properties. Thermogravimetric analysis (TGA) validates the extent of chemical grafting and physical interlocking detected in FTIR and DSC. Scanning electron microscopy (SEM) is used to analyze the morphology and phase separation. The novel approach of overwhelmed physical interlocking and minimum chemical grafting for manufacturing 3D printing blends results in high structural stability (mechanical and intermolecular) against thermal degradation as compared to neat PLA.

Preparation of Triple-Functionalized Montmorillonite Layers Promoting Thermal Stability of Polystyrene

The objective of this study was to investigate the effect of three different treatments on the morphology, microstructure, and the thermal characteristics of a montmorillonite (Mt) sample, by using hydrochloric acid (HCl), tributyl tetradecyl phosphonium chloride (TTPC) surfactant, and γ-methacryloxypropyltrimethoxysilane (γ-MPS). The resultant nanofillers were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption analysis, X-ray fluorescence spectrometry (XRF), and thermogravimetric analysis (TGA). The results showed that the amount of chemical grafting of the γ-MPS was increased after the acid treatment, whereas the amount of intercalation of the TTPC surfactant was decreased. The preintercalation of TTPC or silylation of γ-MPS, for the Mt sample, had a certain hindrance effect on its subsequent silylation or intercalation treatments. Furthermore, the effect of four different nanofillers on the thermal stability properties of the polystyrene (PS) matrix were also investigated. The results showed an increase in thermal stability for the triple-functionalized Mt, compared with the double-functionalized samples. The onset decomposition temperatures and the maximum mass loss temperatures of the PS nanocomposites were increased by 27 °C and 32 °C, respectively, by the incorporation of triple-modified Mt, as a result of the good exfoliation and dispersion of the nanolayers, more favorable polymer–nanofiller interaction, as well as the formation of a more remarkable tortuous pathway in the continuous matrix.

Effective Removal of Calcium and Magnesium Ions from Water by a Novel Alginate–Citrate Composite Aerogel

In this work, a novel alginate/citrate composite aerogel (CA–SC) was synthesized by chemical grafting technology combined with vacuum freeze-drying method, and CA–SC was used for removing calcium (Ca2+) and magnesium (Mg2+) ions from water. The experimental results indicate that the as-prepared CA–SC has a high affinity for Ca2+ and Mg2+ and can remove 96.5% of Ca2+ (or 96.8% of Mg2+) from the corresponding solution. The maximum adsorption capacities of CA–SC for Ca2+ and Mg2+ are 62.38 and 36.23 mg/g, respectively. These values are higher than those of the most reported Ca2+-sorbents and Mg2+-sorbents. The CA–SC adsorbent can be regenerated through a simple pickling step, and its adsorption performance keeps stable after repeated use. Analysis of the adsorption mechanism shows that the CA–SC combines Ca2+ and Mg2+ in water mainly through coordination effect.

Novel Chemical Architectures Based on Beta-Cyclodextrin Derivatives Covalently Attached on Polymer Spheres

This study presents the synthesis and characterization of polymer derivatives of beta-cyclodextrin (BCD), obtained by chemical grafting onto spherical polymer particles (200 nm) presenting oxirane functional groups at their surface. The polymer spheres were synthesized by emulsion polymerization of styrene (ST) and hydroxyethyl methacrylate (HEMA), followed by the grafting on the surface of glycidyl methacrylate (GMA) by seeded emulsion polymerization. The BCD-polymer derivatives were obtained using two BCD derivatives with hydroxylic (BCD-OH) and amino groups (BCD-NH2). The degree of polymer covalent functionalization using the BCD-OH and BCD-NH2 derivatives were determined to be 4.27 and 19.19 weight %, respectively. The adsorption properties of the materials were evaluated using bisphenol A as a target molecule. The best fit for the adsorption kinetics was Lagergren’s model (both for Qe value and for R2) together with Weber’s intraparticle diffusion model in the case of ST-HEMA-GMA-BCD-NH2. The isothermal adsorption evaluation indicated that both systems follow a Langmuir type behavior and afforded a Qmax value of 148.37 mg g−1 and 37.09 mg g−1 for ST-HEMA-GMA-BCD-NH2 and ST-HEMA-GMA-BCD-OH, respectively. The BCD-modified polymers display a degradation temperature of over 400 °C which can be attributed to the existence of hydrogen bonds and BCD thermal degradation pathway in the presence of the polymers.