Second-generation poly(amidoamine) dendrimer (PAMAM G2) 0.5, 1.0, and 2.0 w/v% covalently grafted onto commercial membranes as thin-film composites (TFCs) of polyamide was used to modify the surface of commercial TFC polyamide to increase the forward osmosis (FO) performance. The attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy (increasing amide peak intensities) and X-ray photoelectron spectroscopy (XPS) (appearance of C─N peak and increase of O/N ratio) confirmed successful grafting. Measurements of contact angle showed that there was an increase in hydrophilicity to a maximum of 1 w/v% PAMAM with a slight increase to 2 w/v% as a result of intermolecular hydrogen bonding of terminal amine groups. Scanning electron microscopy (SEM) and AFM results indicated that the TFC-2% PAMAM membrane had more smoother surfaces and a much lower roughness (Ra had reduced to 40.9 nm). The TFC-2% PAMAM membrane demonstrated the best balance between water flux (6.5 + 0.8 LMH versus 5.5 + 0.9 LMH with pristine TFC for draw and feed respectively) and reverse salt flux (0.33 + 0.3 gMH versus 0.051 + 0.08 g/L), as well as in the case of FO test with a draw solution of 1 M sodium chloride (NaCl) and deionized (DI) water feed. Reverse osmosis (RO) mode intrinsic property measurements demonstrated that the modified membrane had a higher salt rejection (99.12% vs. 98.22) and a lower B/A ratio (0.187 vs. 0.381 bar) and lower dilutive internal concentration polarization (ICP; K = 0.237 vs. 0.323 LMH−1). The test of antifouling using 200 mg/L bovine serum albumin (BSA) showed better fouling resistance where the flux recovery ratio (FRR) improved to 83.6% (pristine) and 90.7% (TFC-2% PAMAM) due to increased surface hydrophilicity and smoothness which developed a strong hydration layer. The findings indicate that surface grafting using 2 w/v% PAMAM G2 is an easy yet very useful method to enhance the ability to enhance water flux, salt rejection, and antifouling characteristics of TFC membranes when used in the FO desalination and reuse of water processes.
The use of natural resources for the production of biodegradable packaging is currently the focus of extensive scientific research aimed at providing a sustainable alternative to petrochemical-derived plastics. In this context, this study investigates a biocomposite film using Manihot esculenta starch (MS) as the matrix, reinforced with Rhecktophyllum camerunense (RC) fibers. The RC fibers were extracted via stagnant water retting for 12 days. The composites were fabricated using the solution casting method, with MS as the matrix, glycerol as the plasticizer, and RC fibers (mesh size ≤ 0.30 mm) as reinforcement. Three fiber content levels were studied (3, 6, and 9 wt% relative to the dry starch weight). The glycerol-to-starch and water-to-starch mass ratios were set at 30 wt% and 2000 wt%, respectively. The composites’ physical, chemical, and mechanical properties were characterized according to standardized protocols. The results revealed comparable chemical structures across all formulations. Notably, the composite containing 3 wt% RC fibers (ARC3) demonstrated optimal strength and flexibility, with a tensile strength of 19.99 MPa, a Young’s modulus of 395.25 MPa, and an elongation at break of 47%, making it the most balanced in terms of mechanical performance. Consequently, the ARC3 formulation is recommended for biodegradable packaging applications.
Although air layers are known to improve thermal protection, the influence of engineered air-cavity volume in double-layer polyimide/wool fabrics on the combined flame-retardant, thermal-insulating, and comfort performance remains poorly understood. This study addresses this gap by systematically designing hexagonal air-cavity structures through the differential shrinkage of polyimide and wool fibers. Experimental characterization and finite element analysis demonstrated that optimizing cavity volume significantly improved multifunctional performance. The fabric with the largest air cavity exhibited a 30%–40% reduction in damage length, a 32.2% decrease in peak heat release rate (PHRR), and a 59.6% reduction in smoke production. Infrared thermography and thermal protection tests further showed a 13.0% improvement in insulation rate and a 15.8% increase in thermal protection performance (TPP). Air and moisture permeability were also enhanced, demonstrating improved wearer comfort without compromising protection. These findings establish the critical role of engineered air-cavity volume in balancing thermal insulation, flame retardancy, and comfort, providing a practical design strategy for advanced protective textile systems.
Rubber matrix was controlled to be hydrophilic, swellable, and conductive, by mixing with varied amounts of epichlorohydrin rubber (GECO), polyethylene oxide (PEO), and ethylene–vinyl acetate (EVA) polymers, et cetera. Higher concentration of the epichlorohydrin rubber (GECO) resulted in higher curing times (ts2 and t90), high torque values (ML, MH, and ∆M), high crosslinking density, and higher stiffness (MPa). Sample GP1 recorded highest strength due to the high content (70 part per hundred of rubber [phr]) of the epichlorohydrin rubber (GECO). All the compositions exhibited wetting and hydrophilic behavior, with contact angle < 80°, upon submerging into petrol, diesel, kerosene, cooking oil, and water, respectively. The swollen composites resulted in volume increase, and dramatic drop in the electrical resistances. Based on volume strain (∆V/Vo), the gauge factor (GF = [∆R/Ro/(V/Vo]) deduced for the compounds was within approximately 1.3 × 103–9.6 x 103, which is the first to be reported for liquids (petrol, diesel, kerosene, cooking oil, and water), to the best of our knowledge. These GF values were higher and comparable to many other strain gauges made of rubber-reinforced/coated with graphene, and carbon nanotubes (CNTs), et cetera. Thus, the current compositions exhibit multifunctional capabilities for liquid/chemical sensing, soft robotics, agro-mulching, and real-time soil moisture monitoring applications.
Due to the fascinating behavior of the late-transition-metal (LTM) catalysts for co-/homo-polymerization of olefins, especially polar monomers, they have consistently attracted researchers’ attention. Synergistic effects between the active metal centers have further augmented this interest. Among these structures, oxo-nitrogenated cobalt (II) catalysts are widely used for the polymerization of dienes. Herein, we report the synthesis of an oxo-nitrogenated dinuclear Co(II) catalyst, which was carefully characterized using 1H NMR, Fourier transform infrared (FT-IR), energy dispersive X-ray (EDX), mass, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The catalyst was tested for the polymerization of methyl methacrylate (MMA), a widely used monomer for producing polymethyl methacrylate (PMMA), a transparent thermoplastic with high chemical and thermal stability used in coatings, optics, and biomedical applications, in the presence of a modified methylaluminoxane (MMAO), the cocatalyst. The highest activity was obtained at an [Al]/[Co] molar ratio of 1000:1, Tp = 40°C, and tp = 2 h, giving 66.9 g PMMA/mmol Cat h. Interestingly, the morphology of the given sample particles was spherical under specific conditions. The microstructure study of the PMMA made by the catalyst showed syndiotactic at 57.3%, atactic at 29.5%, and isotactic at 13.1%, respectively. In addition, the microstructural analyses of PMMA exhibited branching densities in the range of 221–330/1000C, a narrow PDI of 1.93, and a molecular weight of M¯w = 1.180 × 105 g/mol for the given samples. Although no evidence of a cooperative effect was observed in terms of selectivity, the reasonable activity of the catalyst may suggest the presence of such an effect.
