Hexamethylenediamine Research Articles

A novel energy-saving and emission-reduction strategy based on facile preparation of thermal insulation coatings doped with modified vacuum ceramic microbeads for concrete protection

The development of thermal insulation protective coatings suitable for constructions and buildings offers a multifaceted approach: it substantially reduces indoor temperatures, enhances residential comfort, decreases air conditioning energy consumption, and conserves energy. Additionally, these coatings provide robust resistance against corrosive substances, thereby significantly prolonging the service life of concrete. In this work, the modification of vacuum ceramic microbeads (VCM) through the polymerization of catechol and hexamethylene diamine to form poly(catecholamine) (PCA) was investigated by FT-IR, XRD, and TEM analysis. Increased levels of incorporation of VCM@PCA further decreased thermal conductivity and increased surface hydrophobicity, while excessive incorporation detrimentally affected the coating's mechanical properties. PDMS/VCM@PCA coating demonstrated exceptional thermal insulation performance, reducing coating temperature by 15.9 °C under simulated sunlight exposure, and in outdoor experiments, the interior temperature of the simulated house with this coating was 4.2 °C lower than the external temperature, highlighting its potential for energy conservation, emission reduction, and building temperature regulation. Additionally, PDMS/VCM@PCA coating provided excellent protection for concrete structures, significantly enhancing abrasion resistance. It also improved the interfacial adhesion between the organic layer and concrete under dry, wet, and 10% NaCl immersion conditions. The addition of VCM@PCA further enhanced resistance to chloride ion penetration, effectively reducing chloride ingress. This thermal insulation protective coating presents a novel strategy for energy conservation, emission reduction, and sustainable development in the civil construction industry.

Evaluation on potential application of lipase immobilized on rice husks in enzymatic glycerolysis reaction

Owing to high production cost and low reaction yield, immobilized lipase is rarely used in industrial glycerolysis. This research characterizes the performance of lipase immobilized on rice husk in glycerolysis reaction. By utilizing hexamethylenediamine (HMDA) and glutaraldehyde (GA) as coupling agents, lipase from Thermomyces lanuginosus was immobilized on oxidized rice husk (ORH). For comparison, another sample was prepared where the lipase was directly immobilized on ORH without the use of HMDA and GA. Then, monoglyceride production was performed via glycerolysis using the immobilized lipase. The FTIR analysis verify interactions on rice husk including rice husk oxidation, HMDA coupling, GA activation and lipase immobilization on rice husk. The study found that within the examined range of added lipase for immobilization (10–40 mg-protein/g-support), ORH–HMDA–GA–Lipase possessed superior outcomes in terms of protein loading, immobilization yield, and recovered glycerolysis activity compared to ORH–Lipase. Besides, ORH–HMDA–GA–Lipase exhibits better storage stability (60°C, 44.9 %) and higher reusability (90.0 % monoglyceride yield at the 8th cycle) against ORH–Lipase. The results confirm satisfying performance of the prepared immobilized lipase in glycerolysis and highlight its enhancements facilitated by coupling agents.

Eco‐friendly synthesis of non‐isocyanate polyurea using PET and CO2 upcycling: A double green approach

AbstractFrom the perspective of sustainability, this research explored both the recycling of polyethylene terephthalate (PET) and the conversion of carbon dioxide (CO2) into polymer materials. To this end, a series of copolyurea specimens were synthesized through the polycondensation of carbon dioxide with hexamethylenediamine (HDA) and terephthalic dihydrazide (TDH), where TDH was derived from the chemical recycling of PET via the aminolysis method. FTIR spectroscopy, 1H NMR, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) characterized the products of PET recycling and synthesized copolyureas. Additionally, we sought to identify the optimal parameters for both the recycling and copolymerization processes. The results of identification analyses for both the recycling and copolymerization reactions confirmed the formation of the desired structures. An increase in the hard segment (TDH) led to discrepancies between the intended and actual monomer ratios in the synthesis, possibly due to dimethyl sulfoxide (DMSO) solubility issues or unreacted TDH. Furthermore, the TGA analysis indicated that the initial degradation temperature (Td,5%) of the copolymer increased with the proportion of aromatic rings in the hard segment, underscoring the complex interactions within the copolymer matrix affecting its thermal and structural properties. The DSC results revealed that for copolyureas with the formula HDAxTDH100–x (where x = 50, 60, 70, 80, 90), reducing the x fraction or increasing the TDH content lowered the melting temperature. Furthermore, at a high percentage of TDH, the melting point disappeared entirely due to the destruction of the crystalline structure, indicating a critical threshold where the copolymer transitions from a semi‐crystalline to an amorphous state.

Leveraging an innovative process integration using highly acid-immune blend membranes for enhanced acid recovery and selective salt separation

We investigate the efficiency and advantage of the integrated diffusion dialysis-electrodialysis (DD-ED) system over the DD process for acid recovery with highly acidic wastewater. The investigation uses various acid (HCl/H2SO4) /salt mixtures encompassing iron, copper and aluminium salts (FeCl2, CuCl2, AlCl3, and FeSO4) as simulated feed. The membrane is prepared using blend mixture of polyvinylidene fluoride (PVDF) and polymethyl methacrylate-co-poly chloromethyl styrene copolymer (PMMA-co-PCMSt) solution by non-solvent induced phase inversion on a nonwoven fabric followed by treatment with different tertiary amines. Representative AEM-Q3 membrane prepared by the post modification of blend membrane with a mixture of N, N, N’, N’- tetramethyl diamino hexane (TMDAH) and trimethyl amine (TMA) (1: 1 w/w %) exhibited the best-balanced performance. The membrane recovered a 84.2% AR (%) of acid with 96.28% purity (%) at a flux (JH+) of 7.08 × 10-4 mol cm-2 h-1 from 3 M HCl and 0.2M FeCl2 mixture making it suitable for further studies. A comprehensive comparative study drawn between the DD and integrated DD-ED showed that there was a 2.3 fold increment in acid recovery for the integrated process over the DD process (for the HCl-FeCl2 system). The membranes have also shown good monovalent (Cl-) and bivalent (SO42-) anion selectivity of 7.8. However, the selectivity was further improved to 12.28 by modification of AEM-Q3 membrane, which is double side cast (referred as AEM-Q3/b). The synthetic strategy of the membrane is easy and scalable and has potential for both acid recovery and selective salt separation by ED process.

Use of commercial synthetic filament waste to reinforce biobased poly(butylene succinate) with the aid of compatibilizers

Since poly(butylene succinate) (PBS) has low rigidity for engineering application, this research attempted to reinforce PBS with poly(ethylene terephthalate) (PET) and polyamide-6 (nylon6) filaments with the reservation of polymer toughness. Filaments were chopped to be short fibers (length of 2 mm to 4 mm) and melt compounded with PBS pellets in the weight ratio of 1 wt%, 5 wt%, and 7 wt% using a twin-screw extruder that the temperature profile was set high enough for melting only PBS matrix. Two types of compatibilizers; hexamethylene diisocyanate (HMDI) or hexamethylene diamine (HMDA) of 0.05 wt% were used to treat fiber surface. It was found that tensile modulus of PBS increased with respect to fiber concentration, which untreated PET fibers provided higher tensile modulus about 2% to 7%. Surface treatment of fibers with either HMDI or HMDA increased rigidity of the composites, while elongation at break and impact strength were also improved with respect to fiber concentration. Also, shifting in glass transition temperature of PBS by DMA indicated improved interfacial interaction, which HMDA treatment gave the best benefit for mechanical properties. Number-average molecular weight of HMDI-treated composites was closed to extruded PBS, however, those of HMDA-treated composites were reduced dramatically implying chain scission highly occurred. SEM micrographs revealed good interfacial adhesion obtained after fiber treatment. Crystallization of PBS studied by XRD showed that the crystal form was not affected by the compatibilizer.

A novel two-step process for the synthesis of hexamethylenediamine from 6-hydroxyhexanenitrile derived from ε-caprolactone

Hexamethylenediamine (HMDA) is an important chemical product for the production of various value-added chemicals especially in the manufacture of polyamides, and its current production mainly relies on the hydrogenation of adiponitrile (ADN). However, the processes for the production of ADN are complicated and monopolized by some transnational corporations. In this work, a novel two-step synthesis of HMDA, consisting of the aerobic oxidation of 6-hydroxyhexanenitrile (6-HHN) to 5-cyanopentanal (5-CPA) and the reductive amination of 5-CPA to HMDA, has been developed. The aerobic oxidation of 6-HHN to 5-CPA was readily realized in an excellent yield of 92.2% under the catalysis of a classic catalyst system Fe(NO3)3/4-AcNH-TEMPO/NaCl under mild conditions. The reductive amination of 5-CPA to HMDA was conducted over a bimetallic Ni30Co7/SiO2, and the conversion of 5-CPA was 99.0% with a HMDA selectivity of 89.5% under optimal parameters. The characterization results show that Ni and Co are mainly present in the form of a Ni-Co alloy. The formation of the Ni-Co alloy in the catalyst Ni30Co7/SiO2 endows with a synergistic effect between Ni and Co in the reductive amination of 5-CPA to HMDA. Catalyst deactivation occurs during catalytic run. Deactivation is mainly due to the metal agglomeration, the oxidation of Ni0 to Ni2+, and the carbon deposition. Deactivated catalysts can be completely regenerated by H2 high-temperature reduction.

Carbon dioxide‐based poly(hydroxyurethane‐urea) elastomers: Synthesis, microphase structure, and properties

AbstractCompared with isocyanate‐based polyurethanes (PUs), poly(hydroxyurethane)s (PHUs) are more likely to form phase mixing structure, inducing poor elastic properties. To avoid this, stronger interaction between hard segments is required. Herein, carbon dioxide‐based poly(hydroxyurethane‐urea)s (PHUUs) with different hard segment contents were prepared through polyaddition reaction using 5‐membered dicyclic carbonate (BADC) as hard segment, poly(propylene glycol) bis(2‐aminopropyl ether) (D2000) as soft segment, and amino‐terminal polyurea oligomer (HMDA*) chain extender, and several PHUs were prepared by using hexamethylenediamine (HMDA) chain extender or without using chain extender as controls. The interaction between hard segments were strengthened with the introduce of chain extender. Compared with PHUs, PHUUs with HMDA* chain extender were more inclined to form significant microphase separation. For PHUUs, the hard segment Tg appeared at around 60°C when hard segment content reached 40 wt%, and the interdomain spacings were in the range of around 14–23 nm with 40–50 wt% hard segment content. In addition, PHUUs exhibited better solvents resistance and mechanical properties than PHUs with the same hard segment content. PHUUs with certain hard segment content showed good elastic recovery, with a residual strain less than 2% after 10 cycles, which comparable with conventional isocyanate‐based PUs.

Carbonated castor oil as a bioplasticiser and toughening agent for bisphenol a based epoxy

AbstractDiglycidyl ether of bisphenol A (DGEBA), a key intermediate for epoxy resins, provides strong adhesion, processability and the resulting thermoset boasts high cross linking density. However, the inherent brittleness and susceptibility to cracking restrict its advanced applications. To overcome these drawbacks, CO2 fixed cyclic carbonate from castor oil (CCO) was synthesized from epoxidised castor oil (ECO) and used in varying quantities as a toughening agent for amine cured DGEBA. Different amines have been utilized to cure the epoxy and to study the structure–property relationship by fixing the amount of CCO. The inclusion of 10% CCO resulted in improvement in the tensile strength, storage modulus, flexural modulus, and impact strength of the epoxy‐urethane hybrid. Moreover, the epoxy‐urethane networks had reduced cross linking density imparted by the fatty acid units of CCO and the presence of unreacted carbonate groups facilitated molecular movement, thereby contributing to energy dissipation during the deformation process. Further incorporation of the CCO lowers the mechanical properties of the hybrids due to a reduction in cross linking density. Trimethylolpropane tris[poly(propyleneglycol)amine terminated] ether cured system exhibited the highest thermal stability compared to hexamethylene diamine, isophorone diamine, and 4,7,10‐trioxa‐1,13 tridecanediamine. The Tg decreased as the CCO content increased, while the water contact angle increased.

Highly efficient selective hydrogenation of adiponitrile to hexamethylene diamine over barium and melamine formaldehyde resin-modified nickel–cobalt-based zeolitic imidazolate framework-derived catalyst

In the present study, the catalyst modified with alkaline oxide can enhance the selectivity to primary amines. However, the addition of alkaline oxide inevitably reduces catalytic activity. In this study, NiCo-NC@BaO-MFC catalyst derived from zeolitic imidazolate framework-67, Ba(CH3COO)2, and melamine formaldehyde (MF) resin was prepared and used for the hydrogenation of adiponitrile (ADN) to hexamethylene diamine (HDMA). The carbon layer obtained from the MF resin effectively prevents the interaction between barium (Ba) and the active center, thus improving target product selectivity without decreasing catalytic activity. The results of the density functional theory (DFT) calculation and characterization indicated that the effect of synergy between nickel (Ni) and cobalt (Co) bimetals induces an electron density growth on the Ni surface, bringing the d-band center toward the Fermi surface. Meanwhile, the high electron density of the active center compensates for the electron-deficient state of the carbon atom in –CN, thus improving the catalytic activity. Furthermore, it was found that the introduction of Ba promotes the formation of nucleophilic hydrogen anions, which facilitates the hydrogenation of 6-aminohexylimine (AHIM) to HDMA and inhibits the intramolecular condensation of AHIM, hence improving the selectivity to HDMA. The NiCo-NC@BaO-MFC catalyst gives 98.6 % ADN conversion and 97.2 % selectivity to HDMA in an alkali-free system.

Polymeric optical fiber biosensor with PAMAM dendrimer-based surface modification and PlGF detection for pre-eclampsia diagnosis

Pre-eclampsia (PE) is a life-threatening complication that occurs during pregnancy, affecting a large number of pregnant women and newborns worldwide. Rapid, on-site and affordable screening of PE at an early stage is necessary to ensure timely treatment and minimize both maternal and neonatal morbidity and mortality rates. Placental growth factor (PlGF) is an angiogenic blood biomarker used for PE diagnosis. Herein, we report the plasmonic fiber optic absorbance biosensor (P-FAB) strategy for detecting PlGF at femtomolar concentration using polymethyl methacrylate (PMMA) based U-bent polymeric optical fiber (POF) sensor probes. A novel poly(amidoamine) (PAMAM) dendrimer based PMMA surface modification is established to obtain a greater immobilization of the bioreceptors compared to a linear molecule like hexamethylenediamine (HMDA). Plasmonic sandwich immunoassay was realized by immobilizing the mouse anti-PlGF (3H1) on the U-bent POF sensor probe surface and gold nanoparticles (AuNP) labels conjugated with mouse anti-PlGF (6H9). The POF sensor probes could measure PlGF within 30 min using the P-FAB strategy. The limit-of-detection (LoD) was found to be 0.19 pg/mL and 0.57 pg/mL in phosphate-buffered saline and 10× diluted serum, respectively. The clinical sample testing, with eleven positive and eleven negative preeclamptic pregnancy samples, successfully confirmed the accuracy, reliability, specificity, and sensitivity of the P-FAB based POF sensor platform, thereby paving the way for cost-effective technology for PlGF detection and its potential for pre-eclampsia diagnosis.

Post-combustion CO2 absorption-desorption performance of novel aqueous binary amine blend of Hexamethylenediamine (HMDA) and 2-Dimethylaminoethanol (DMAE)

In this investigation, a novel aqueous Hexamethylenediamine (HMDA) and 2-Dimethylaminoethanol (DMAE) amine blend was made to capture CO2, which would strongly contribute towards net-zero emission. The capability of the novel amine blend was investigated by conducting CO2 absorption and desorption experiments. The major research findings were equilibrium CO2 loading (α), cyclic capacity, heat duty, regeneration efficiency, CO2 absorption and desorption rate, pH, density, 13C NMR and FTIR characterization, process optimization, and toxicity assessment. CO2 absorption experimental operating conditions: temperature (T) = 298.15–333.15 K, CO2 partial pressure (PCO2) = 10.13–25.33 kPa, mole fraction of HMDA (mHMDA) = 0.05–0.20, and solution concentration (C) = 1–3 mol/L. The optimum equilibrium CO2 loading was found to be 1.2174 mol CO2/mol amine at T = 298.15 K, PCO2 = 25.33 kPa, mHMDA = 0.20, and C = 1 mol/L. Similarly, desorption experiments were performed at constant T = 393.15 K and PCO2 = 25.33 kPa. For C = 3 mol/L, cyclic capacity was 1.5951 mol CO2/L solution, which was 61.77 % higher than the benchmark 30 wt% monoethanolamine (MEA). The heat duty and regeneration efficiency for 3 mol/L solution were calculated to be 131.24 kJ/mol CO2 and 60.47 %, respectively. The novel amine blend's heat of CO2 absorption was calculated to be −75.50 kJ/mol. Response surface methodology (RSM) was used for modeling and optimization: αoptimum = 1.04583 mol CO2/mol amine at T = 306.90 K, PCO2 = 21.53 kPa, mHMDA = 0.16 and C = 1.5 mol/L.

Studying the Structure and Properties of Epoxy Composites Modified by Original and Functionalized with Hexamethylenediamine by Electrochemically Synthesized Graphene Oxide.

In this study, we used multilayer graphene oxide (GO) obtained by anodic oxidation of graphite powder in 83% sulfuric acid. The modification of GO was carried out by its interaction with hexamethylenediamine (HMDA) according to the mechanism of nucleophilic substitution between the amino group of HMDA (HMDA) and the epoxy groups of GO, accompanied by partial reduction of multilayer GO and an increase in the deformation of the carbon layers. The structure and properties of modified HMDA-GO were characterized using research methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy and Raman spectroscopy. The conducted studies show the effectiveness of using HMDA-OG for modifying epoxy composites. Functionalizing treatment of GO particles helps reduce the free surface energy at the polymer-nanofiller interface and increase adhesion, which leads to the improvement in physical and mechanical characteristics of the composite material. The results demonstrate an increase in the strength and elastic modulus in bending by 48% and 102%, respectively, an increase in the impact strength by 122%, and an increase in the strength and elastic modulus in tension by 82% and 47%, respectively, as compared to the pristine epoxy composite which did not contain GO-HMDA. It has been found that the addition of GO-HMDA into the epoxy composition initiates the polymerization process due to the participation of reactive amino groups in the polymerization reaction, and also provides an increase in the thermal stability of epoxy nanocomposites.

Biobased Imine Vitrimers Obtained by Photo and Thermal Curing Procedures-Promising Materials for 3D Printing.

Imine-based vitrimers were prepared from synthesized diimine-dimethacrylate monomer derived from biobased vanillin. First, a methacrylate derivative starting from vanillin was synthesized. The diimine derivative was synthesized by condensation of the aldehyde groups from two vanillin methacrylate units with the amine groups of hexamethylenediamine (HMDA). The synthesized product was used in formulations containing ethylene glycol phenyl ether methacrylate (EGPMA) as a reactive diluent for the customization of final material properties and cured by exposure to ultraviolet (UV)-light using suitable radical photoinitiators or else with temperature using a radical thermal initiator. Materials with glass transition temperatures (Tgs) ranging from 70 to 90 °C were prepared, showing good thermal stability and mechanical and thermomechanical properties. The evaluation of their vitrimeric characteristics revealed that all materials achieved a stress-relaxation factor (σ = 0.37σ0) in less than 130 s at 160 °C, with photocured materials exhibiting faster relaxation rates. The catalytic effect of phosphine oxide groups in imine metathesis has also been evidenced. All prepared materials could be mechanically recycled and completely solubilized in a two-step degradation process, putting evidence of their potential use for carbon fiber-reinforced composites (CFRCs). In addition, they demonstrated promising self-repairing abilities. Finally, as a proof of concept, it was established that these formulations could be effectively processed using a Digital Light Processing three-dimensional (3D) Printer (DLP), resulting in the fabrication of complex shapes with high resolution.

Aminopoly(carboxylic acid)-Functionalized PolyHIPE Beads toward Eliminating Trace Heavy Metal Ions from Water.

Many advanced materials are designed for the removal of heavy metal ions from water. However, materials for eliminating trace heavy metal ions from wastewater to meet drinking water standards remain a major challenge. Herein, epoxy group-functionalized open-cellular beads are synthesized by UV polymerization of a water-in-oil-in-water system. The epoxy groups are further transformed into diethylenetriaminepentaacetic acid (DTPA) with hexamethylene diamine as a bridging agent. The resulting material (DTPA@polyHIPE beads) can eliminate trace Cu(II), Cr(III), Pb(II), Fe(III), or Cd(II) from water. When 0.15 g of DTPA@polyHIPE beads are used to adsorb metal ions of 20 mg in 100 mL of water, the residue concentrations of Cu(II), Cr(III), Pb(II), Fe(III), and Cd(II) are reduced to 0.08, 0.06, 0.02, 0.09, and 0.07 mg/L, respectively. The adsorption efficiencies of the beads for these ions are all higher than 99.55%. The adsorbent is durable and exhibits good recyclability by retaining an adsorption capacity of ≥91% after 5 cycles. The negative values of ΔG in the adsorption process indicate that the adsorption is feasible and spontaneous. The chemical adsorption follows the Freundlich adsorption model, indicating a multilayer heterogeneous adsorption. The DTPA@polyHIPE beads have a great potential application in dealing with trace heavy metal ion polluted water.

Construction of Oxygen Vacancy-Rich TiO2 Nanocrystals for Boosting the Ammonolysis of Caprolactam to 6-Aminocapronitrile.

Hexamethylene diamine, an important chemical intermediate for polyamides, can be synthesized through the two-step route of caprolactam (CPL) ammonolysis to 6-aminocapronitrile (ACN), followed by hydrogenation. This method has received increasing attention from academia and industry. However, studies on the catalyst structure-performance correlation in CPL ammonolysis are still sporadic. In this work, a series of anatase TiO2 with different oxygen vacancy concentrations was prepared by chemical reduction using NaBH4. The oxygen vacancy on TiO2 surface, presented as Ti3+ sites, substantially enhances the adsorption and activation of NH3, which are demonstrated as the key steps in ammonolysis. Owing to the synergistic effect of Ti3+ and Ti4+ species, the CPL conversion rate and ACN selectivity of 85 and 97%, respectively, are achieved within 250 h. Density functional theory calculations showed that the intermediates on oxygen vacancy-rich TiO2 had a more favorable adsorption energy compared to those on intact TiO2, which is in good agreement with the experimental results.

Regulating the coordination environment of Co@C catalysts for selective hydrogenation of adiponitrile to hexamethylenediamine

Selective production of hexamethylenediamine (HMDA) by hydrogenation of adiponitrile (ADN) is a precondition to produce high-value added polyamides (e.g., nylon-66) and is still a great challenge by metal catalyst under alkali-free condition. Rational design of metal reactive center via modulated coordination endows a practical cure. We presented the significant role by forming Co-Nx coordinated sties in heterogeneous Co@C catalysts, which induced well crystallization of metallic Co phase with high-yield of HMDA under ultrafast intrinsic reaction rate (TOF of 2746 h−1). Characterizations suggested the simultaneous reduction of Coδ+ accompanied with carbon decomposition during pre-reduction, resulting in the strong Co-C interaction via Co-Nx coordination. Fine and stable Co particles around 5 nm were confined by mesoporous carbon layers with clear lattice distortion/expansion at Co-C interface. DFT calculation confirmed the electron modulation on the d-band center of Co with the strong affinity toward semi-hydrogenated ACN, facilitating the in-depth hydrogenation to HMDA. The Co coordinated states tuned by N was a fine regulator to modulate the spatial and electronic structure of Co active sites, positively correlating with the intrinsic activity. The Co@C-Z400 transformed ADN to HMDA with 90.7 % yield under sharply reduced activation energy of 37.9 kJ/mol.

Solid-state crosslinking of thin film composite membranes for organic solvent reverse osmosis separations

Organic solvent separations are energy intensive yet ubiquitous unit operations in the chemical, petrochemical, and pharmaceutical industries. Membrane technology can significantly reduce the demands for energy, carbon, and water in these operations. However, the separation of similar molecules is often required, which is a difficult challenge for membranes. Some polymers used in organic solvent reverse osmosis (OSRO) have been known to suffer from plasticization and dilation, making them inefficient for these molecular separations. Here we describe a method to address this problem by uniformly crosslinking a selective layer of a thin film composite (TFC) membrane to improve stability in organic solvents and tune separation performance. Crosslinking agents hexamethylene diamine, p-xylylene diamine, and 4,4′-biphenyldicarbontrile diamine, protected as N-tert-butyloxycarbonyl (Boc) carbamates, were introduced to the commercial polymer Matrimid® 5218. Boc protection rendered them sufficiently soluble in the polymer matrix to obviate costly liquid-phase crosslinker infusion steps. After casting, the amines within the membrane were thermally deprotected to induce a solid-state crosslinking reaction. The resulting crosslinked TFC membranes showed excellent stability in organic solvents, separation performance with binary (toluene/triisopropylbenzene) and 9-component organic solvent mixtures, and tunable separation characteristics based on the nature and concentration of the crosslinking agent.

Elaboration and characterization of biodegradable poly(aspartic-co-glutamic acid) hydrogels as soil additives with different crosslinkers

This work introduces a promising biodegradable copolymer synthesized through the fusion of D,L-aspartic acid (ASP) and L-glutamic acid (GA) utilizing melt polymerization. Employing infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR), and X-ray diffraction (XRD), the copolymer’s structural characterization highlights its distinctive physicochemical attributes. The synthesis, conducted with a facile and controllable melt polymerization method, yielded a remarkable product yield of up to 81%. The optimization of water absorption properties involved a meticulous exploration of various diamine cross-linking agents—hexamethylene diamine (HMD), lysine (LYS), and a synthesized tartaric acid dihydrazide (TD) derivative. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), and scanning electron microscopy (SEM) were employed to confirm the copolymer’s structure, morphology, and cross-linking efficiency. The findings underscore exceptional water retention capabilities, with a peak swelling ratio of 11.874% achieved at a 10% concentration of hexamethylene diamine. Beyond advancing superabsorbent materials, this study contributes to mitigating environmental concerns associated with non-biodegradable alternatives.

Comparing three strategies for surface treatment of Mg coated by hexamethylene diamine tetra methylene phosphonic acid for corrosion protection

Manufacturing Mg and Mg‐based alloys with controllable degradation rate has always been a challenge. Surface modification is one of the best ways to acquire protection against corrosion. Previously, many approaches such as phosphating (Na3PO4), fluoridation (HF), and alkalization (NaOH) treatments have been used to regulate the corrosion rate. Here, we compare the corrosion rates of 3‐surface modified Mg samples coated with hexamethylene diamine tetra methylene phosphonic (HMDTMPA). The protection of those different layers was ranked in the order: phosphate > alkaline > fluoridation treatment. The chemistry of those chemical conversion layers was discussed in the light of scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS). The mechanism of tailoring a protective film of HMDTMPA on phosphated Mg was discussed according to the ability of P to bridge the substrate with the coating.

Circulating-infiltrating preparation of hydrophilic nylon 6 membrane to hydrophobic MWCNT@nylon composite membrane

The ion adsorption capacity has been added to the nylon 6 microfiltration (MF) membrane by grafting the fibers in its structure with carboxylated multi-walled carbon nanotubes (MWCNT-COOH). Through a direct three-step functionalization reaction with hexamethylenediamine (HMDA) and MWCNT-COOH, the multi-walled carbon nanotubes grafted nylon (MWCNT@nylon) fibers are made up of original nylon 6 and intermediate amino-enriched (nylon-NH2) membranes. Chemical structure analysis shows that HMDA and MWCNTs were grafted to the nylon 6 fiber side wall, without causing damage to either the nylon 6 backbone or the pore size of the original membrane. The SEM images confirm this and further confirm that the plexus of MWCNT-COOH has a pore size of approximately 50 nm, covering the nylon 6 fibers. The sidewall of nylon-NH2 and MWCNT@nylon fibers contains hydrophilic groups (amino and carboxylic), allowing the as-prepared membranes to reduce the wetting angle from about 70.3° to about 108.1°. This special structure opens new possibilities for polyamide membranes as well as mass production by the proposed simple method.