Superhydrophobic sponges and sponge-like materials have attracted great attention recently as potential sorbent materials for oil spill cleanup due to their excellent sorption capacity and high selectivity. A major challenge to their broad use is the fabrication of superhydrophobic sponges with superior recyclability, good mechanical strength, low cost, and manufacture scalability. In this study, we demonstrate a facile, cost-effective, and scalable method to fabricate robust, superhydrophobic sponges through the silanization of commercial melamine sponges via a solution-immersion process. The silanization was achieved through secondary amine groups on the surface of the sponge skeletons with alkylsilane compounds, forming self-assembled monolayers on the surface of sponge skeletons. This resulted in our ability to tune the surface properties of the sponges from being hydrophilic to superhydrophobic with a water contact angle of 151.0°. The superhydrophobic silanized melamine sponge exhibited excellent sorption capacity for a wide range of organic solvents and oils, from 82 to 163 times its own weight, depending on the polarity and density of the employed organic solvents and oils, and high selectivity and outstanding recyclability with an absorption capacity retention greater than 90% after 1000 cycles. These findings offer an effective approach for oil spill containment and environmental remediation.

Superhydrophobic Silanized Melamine Sponges as High Efficiency Oil Absorbent Materials

An ultrahigh pyridinic N-content-doped porous carbon monolith is reported, and the content of pyridinic N reaches up to 10.1% in overall material (53.4 ± 0.9% out of 18.9 ± 0.4% N content), being higher than most of previously reported N-doping carbonaceous materials, which exhibit greatly improved electrochemical performance for potassium storage, especially in term of the high reversible capacity. Remarkably, the pyridinic N-doped porous carbon monolith (PNCM) electrode exhibits high initial charge capacity of 487 mAh g−1 at a current density of 20 mA g−1, which is one of the highest reversible capacities among all carbonaceous anodes for K-ion batteries. Moreover, the K-ion full cell is successfully assembled, demonstrating a high practical energy density of 153.5 Wh kg−1. These results make PNCM promising for practical application in energy storage devices and encourage more investigations on a similar potassium storage system.

Ultra-High Pyridinic N-Doped Porous Carbon Monolith Enabling High-Capacity K-Ion Battery Anodes for Both Half-Cell and Full-Cell Applications.

K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K+, stable electrode materials capable of sustaining the repeated K+ intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extr...

Engineering Hollow Carbon Architecture for High-Performance K-Ion Battery Anode.

Melamine-derived carbon sponges for oil-water separation

A high-performance anode material, MnNCN, is synthesized through a facile and low-cost method. The relationship between electrochemical properties and chemical composition is explored on the scientific considerations that can provide an insight on designing expected materials. MnNCN with the long bonding length of 2.262 A in MnN and weak electronegativity of 3.04 Pauling units in N leads to a lower charge/discharge potential than that of MnO owing to the character of chemical bonds transformed to covalent dominating from ionic dominating in MnO. Covalent character increases the ratio of sharing electrons that decreases the migration energy of electrons in electrochemical reaction, which enhances the reactive reversibility and stability of electrode material. MnNCN delivered a reversibly specific capacity of 385 mA h g−1 at 5 A g−1 in a Li-ion half cell. Besides, a Li-ion hybrid capacitor with a high voltage of 4 V presents energy and power densities of respective 103 Wh kg−1 and 8533 W kg−1 and cycles at 5 A g−1 without detectable degradation after 5000 cycles.

Exploiting High-Performance Anode through Tuning the Character of Chemical Bonds for Li-Ion Batteries and Capacitors

Melamine formaldehyde (MF) resin was synthesized by the reaction between melamine and formaldehyde under alkaline condition in tetrohydrofuran medium with 1:3 melamine to formaldehyde molar ratio. The synthesized resins were characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Curing and reaction mechanism was studied by thermal and spectroscopic analysis. Two exothermic peaks were observed in the DSC analysis indicating a two-step crosslinking reaction process was correlated to TGA analysis. FTIR studies at different temperatures explained the two-stage curing mechanism which is concurring with the DSC data. At a temperature range of 140–160 °C, reversible demethylolation is dominating to the crosslinking reaction. At temperature >160 °C, the crosslinking reaction dominates. On the basis of DSC and FTIR data, a possible crosslinking reaction route was derived and explained. The first stage of curing is the conversion of methylol groups to primary amine and the second stage is the crosslinking of methylol groups to the final product, methylene bridges. The thermal stability of the methylol groups, methylene bridges and the triazine ring, as well as the evaporation of effluents at different stages of curing, are also discussed based on combined TGA and DSC results. Curing studies and reaction mechanism of MF resin was studied by thermal and spectroscopic tools comparing DSC and FTIR studies explains the two-stage thermal curing mechanism. The first step of thermal curing at temperature range of 140–160 °C is the reverse reaction of methylol groups to melamine and second step occurring at temperature >160 °C is the crosslinking of methylol groups to the final product, methylene bridge. Hence, by the mutual agreement of DSC and FTIR studies, a possible reaction route was derived for the thermal curing process. The DSC–TGA thermogram supports the two-step process of the cure reaction by exhibiting two peaks in the same temperature region.

/pdf/melamine-formaldehyde-curing-studies-and-reaction-mechanism-3il7exblsm.pdf

Melamine formaldehyde: curing studies and reaction mechanism

Composites
based on melamine formaldehyde resins filled with exfoliated graphite or so
called nanographite have been prepared to achieve electrical conductivity and
improve mechanical strength and thermal stability. The nanographite was
synthesized by thermal treatment of oxidized graphite and the incorporation
into the melamine matrix was accomplished during the melamine formaldehyde
reaction. A homogenous dispersion of the filler in the matrix and the forming
of a connecting network based on graphite sheets were proved by SEM images. The graphite filler was able to increase the
flexural strength of molded testing specimens compared to unfilled resins and
electrical conductivity was achieved starting at 2 wt% nanographite.

/pdf/characterization-of-conductive-nanographite-melamine-3m67afwfz2.pdf

Characterization of Conductive Nanographite Melamine Composites

The amount of plastic waste is on the rise each year. It is associated with green house gas emissions and hazardous potential if left untreated at the landfill. Plastic is formed from the polymerization of ethane, essentially fossil fuel based, and with chemical energy content equivalent to diesel fuel, i.e. 43 MJ/kg. Thereby, plastics are excellent candidates/feedstock for energy recovery. This work explores the recycling of cross-linked polyethylene waste-plastic that is generated at a considerable amount from the cable industry. It undertakes thermal analysis of the plastic as the first step using the Differential Scanning Calorimetry (DSC) to observe its thermal conversion and meting temperature. It also undertakes the re-compounding of the waste plastic by infusion the cross-linked polyethylene waste into mini-compounder at different waste-to-virgin polyethylene weight ratio, i. e. 5%, 10%, and 15%. Assessment of the mechanical properties of the compounded product, i.e. recycled mixture, is conducted on standard uniaxial samples using thermo scientific mini extruder, the HAAKE MiniJet II injection molding, and Instron tensile machine. At as high as 15 wt% recyclate to virgin mixture, an increase of 17% in young modulus, 37.2% in yield stress, 22.4% in ultimate stress, and a decrease of 3.3% in the melting point were obtained compared to the virgin/baseline polyethylene. From the resulted stress strain relation Morz bilinear plastic material model constants obtained (Et), that showed 25.6% increase, allowing better investigation of the true stress/strain behavior through FEM numerically simulation.

Recycling of Cross-linked Polyethylene Cable Waste via Particulate Infusion

The use of supercritical difluoromethane (scHFC 32) as a solvent is demonstrated for the polymerisation of methyl methacrylate. It is shown that appreciably higher molecular weight polymer can be obtained using scHFC 32 than scCO2, which is due to the higher solubility of the polymer in the more polar fluid. The solubility of various polymer standards is characterised at two pressures in scHFC 32 and is shown to be appreciable up to a molecular weight of 11 000 g mol−1 whereas in scCO2 the polymer of this mass is shown to be almost totally insoluble.

Polymerisation of methyl methacrylate in supercritical difluoromethane

A recent academic paradigm shift in the United Arab Emirates (UAE) introduced US-style medical education to meet the nation’s growing need for medical practitioners. This newly established Doctor o...

https://journals.sagepub.com/doi/pdf/10.1177/2382120520953119

Sulafudin Vukusic

Papers

Melamine formaldehyde: curing studies and reaction mechanism

Characterization of Conductive Nanographite Melamine Composites

Recycling of Cross-linked Polyethylene Cable Waste via Particulate Infusion

Polymerisation of methyl methacrylate in supercritical difluoromethane

Adapting Premedical Post-Baccalaureate Approaches to Support US-style Medical Education in the United Arab Emirates.