Search

More recently, sp3 defects have been reported to show great potential for enhancing the oxygen reduction reaction (ORR) activity of metal-free carbon catalysts. However, it is still a challenge to increase the sp3 defects for achieving superior ORR activity, especially using organics as precursors by ambient-pressure pyrolysis. Herein, sp3-hybridized C and N enriched melamine–formaldehyde resin microspheres were employed for pyrolysis to increase sp3 defects in derived carbons under activation of urea. Under the synergistic effects of intrinsic characteristics of MF microspheres and the activation of sacrificial urea, the derived carbon was endowed to abundant sp3 defects and N species couple with a hierarchical porous structure. Owing to these specific features, the derived metal-free carbon catalyst showed extremely superior ORR activity, zinc-air battery performance and durability. This study provides an insight into the inheritance of sp3 carbon from the precursor to the sp3 defects in final derived carbon catalysts. The sp3 defects were increased by pyrolysis sp3-hybridized C and N enriched melamine–formaldehyde microspheres under the activation of urea, by which a metal-free carbon catalyst with superior ORR activity was obtained. [ABSTRACT FROM AUTHOR]

An innovative solid-phase microextraction (SPME) fiber coating, melamine–formaldehyde resin (MFR), was synthesized with a green cross-linker (paraformaldehyde), and it exhibited high heat resistance (up to 350 °C). Seven polycyclic aromatic hydrocarbons (PAHs) were chosen as analytes, and the results demonstrated the MFR-based SPME fiber's exceptional enrichment capabilities and efficient extraction, with high enrichment factors and significantly improved efficiency compared to the conventional polydimethylsiloxane (PDMS) fibers. The unique superiority of the MFR was attributed to its strong π–π interactions and amino-associated enhancement, as well as its porous structure and rough surface, which provided abundant adsorption sites and facilitated rapid mass transport of analytes. Furthermore, the preparation conditions of the MFR-coated SPME fiber were compared with those of commercially available and reported fibers, emphasizing the advantages of the MFR-coated fiber, such as its simplicity, cost-effectiveness, reproducibility, and eco-friendliness. The MFR-based SPME fiber exhibited significant advantages, including high enrichment factors (ranging from 1906- to 7153-fold) for PAHs and good fiber-to-fiber reproducibility (8.7–14.6%), outperforming commercially available PDMS fibers by a factor of 4.9–82.8-fold. This study also considered important factors affecting the extraction process, such as ionic strength, temperature, and time, and optimized these parameters for the best extraction efficiency. The greenness of the developed method was assessed using the Analytical Eco-Scale, and the results showed that it was green in terms of reagent dosage, energy consumption, and waste. The developed headspace solid phase microextraction–gas chromatography–tandem mass spectrometry (HS-SPME-GC-MS/MS) method based on the MFR coating exhibited excellent precision, accuracy, and repeatability, making it a reliable method for the determination of trace PAHs in environmental water samples. [ABSTRACT FROM AUTHOR]

The development and characterization of sulfonated melamine formaldehyde resin microspheres (SMF microspheres) as light diffusers in epoxy resin was presented in this paper. The SMF microspheres were prepared through dispersion polymerization with uniform particle size, smooth surface, and a high refractive index. The particle size of the microspheres was controllable within the range from 0.8 to 3.7 µm according to the pH during acidic condensation and the amount of melamine. Compared to traditional MF microspheres, SMF microspheres possessed unique sulfonic acid groups, higher primary amine content, and stronger polarity, which prevent agglomeration when mixed with epoxy resin. The SMF microspheres thus prepared were used as light-diffusing fillers with epoxy resin as matrix. Experimental results and single-particle Mie scattering simulations confirmed that SMF microspheres with a higher refractive index and smaller particle size exhibited higher light-shading efficiency and the haze of EP, demonstrating their outstanding light-diffusing performance. In summary, the significant potential application of SMF microspheres in the field of light diffusers was demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • A core-shell structured piperazine pyrophosphate microcapsules (MT@PAPP) is constructed. • The MT@PAPP enhances the compatibility and mechanical property of TPE/MT@PAPP composites. • Compared with pure TPE, the PHRR and PSPR of TPE/MT@PAPP were reduced by 78.5% and 60.0%, respectively. In this study, core-shell structured piperazine pyrophosphate (PAPP) is designed to enhance the fire safety and mechanical property of styrenic thermoplastic elastomer (TPE) composites. The PAPP is microencapsulated with carbon nanotube modified melamine-formaldehyde resin to prepare core-shell structured flame retardants (MT@PAPP). Due to the excellent compatibility between the MT@PAPP and TPE matrix, the mechanical property of TPE/MT@PAPP is improved. Compared with TPE, the peak heat release rate and peak smoke production rate of TPE/MT@PAPP are decreased by 78.5% and 60.0%, respectively. Thus, the core-shell structured piperazine pyrophosphate microcapsule strategy provides an excellent approach to obtain high-performance TPE composites. [ABSTRACT FROM AUTHOR]

In past research metal selenides have reported versatile results in the field of water splitting. Cobalt di-selenide has received much attention in the oxygen evolution reaction (OER) due to its excellent results towards OER. To excel the reaction capability, herein we have reported CoSe 2, pMF-R and CoSe 2 @pMF-R nanostructures in which the freshly prepared CoSe 2 nanostructures were decorated on the surface of pMF-R (polymerised melamine paraformaldehyde resin). The study showed that the bonds between cobalt and nitrogen were well formed, which is maintaining the improved charge transfer channels to annihilate the barriers between the GC (glassy carbon) electrode surface and active sites of CoSe 2. Because of the coaction of CoSe 2 and pMF-R, the OER calibration of the CoSe 2 @pMF-R catalyst has shown a low onset potential 1.56 V and its electrochemical activity towards OER was found to be much higher as 10 mAcm−2 at 1.608 V Vs. RHE. Operando spectroelectrochemical investigations revealed that active sites of selenium, Co2+, Co3+ and pMF-R available for generation of intermediate oxygen species and responsible for exponential increase in rate of OER. The order of reaction is found to one. The compositional and structural characteristics of CoSe 2 @pMF-R composite over other electrocatalysts is responsible for outstanding electrochemical performance. [Display omitted] • Novel CoSe 2 grafted pMF-R based electrocatalyst (CoSe 2 @pMF-R) for OER is synthesized. • The presence of pMF-R greatly boosts the conductivity of cobalt di-selenide and encourages charge transfer. • Operando spectrochemical studies has done during OER. • The OER has started at very low onset potential (1.56 V). [ABSTRACT FROM AUTHOR]

The dimensional stabilisation of wood using thermosetting resins relies on the resin uptake into the cell walls. This study tested if a conditioning step after the impregnation and before the final heat-curing enhances the cell wall uptake to improve dimensional stabilisation without increasing the chemical consumption. Small blocks of Scots pine sapwood were vacuum-impregnated with an aqueous melamine formaldehyde solution and conditioned at 33, 70, or 95 % RH for up to 1 week before drying and curing the blocks at 103 °C. However, the conditioning step decreased the cell wall bulking and the moisture exclusion effect compared to the immediate heat curing of the impregnated samples. Analyses of the resin-treated samples by scanning electron microscopy, IR spectroscopy and confocal Raman microspectroscopy provided evidence of wood hydrolysis and polycondensation of the resin within the cell lumen during the conditioning step. Hydrolysis and removal of wood constituents may have counterbalanced the cell wall bulking of the resin. Polycondensation of the resin in the lumen increased its molecule size, which could have hindered the cell wall diffusion of the resin. [ABSTRACT FROM AUTHOR]

The resin impregnation treatment of wood is used as a pretreatment to improve the deformability of wood and the durability of its formed products. The objective of this study was to clarify the effect of solvent removal after resin impregnation on wood deformation. A solution of melamine formaldehyde (MF) resin was impregnated into the wood, and the solvent was removed from the wood under vacuum or different relative humidity (RH) conditions. The deformability of MF-resin-impregnated wood was evaluated based on the load required for molding. A higher RH during solvent removal allowed the MF resin to penetrate the cell wall, while the polymerization of the MF resin impregnated in the cell lumen and cell walls was accelerated. Polymerization of the impregnated resin significantly reduced the deformability. The cell orientation and distribution of the MF resin at the cellular level in the molded products were evaluated by X-ray diffraction and Raman mapping. The results showed that the higher the RH during the solvent removal process, the higher the cell orientation and amount of resin in the cell wall. These results suggest that the solvent removal process after resin impregnation has a significant effect on deformability during deformation processing and the formed products. [ABSTRACT FROM AUTHOR]

In this study, a composite modifier for wood impregnation is prepared, which is functional and environmentally friendly. The surface of silica sol was modified by using KH-560. The modified silica sol, melamine, and glyoxal were used as raw materials. The silica sol/melamine glyoxal resin (from now on referred to as Silica sol/MG) composite modifier was prepared based on in-situ polymerization. The physicochemical properties (viscosity, solid content and etc.) of the composite modifier were evaluated. The structural and thermal properties were characterized and analyzed by FTIR spectroscopy, particle size distribution, TG and DSC. The results showed that the viscosity and solid content of the composite modifier decreased with the increase in the mass of the silica sol. The FTIR spectroscopy showed peaks at 473 cm−1 and 1101 cm−1, which were assigned to bending and stretching vibrations of the Si-O-Si bond, respectively, indicating that the modified silica sol was successfully introduced into the MG resin. When the modified silica sol mass fraction was 30%-40%, the particle size distribution of the composite modifier was relatively uniform. TG analysis found that the thermal stability of the composite modifier was significantly improved compared with the unmodified resin. DSC analysis showed that adding the modified silica sol reduced the curing temperature of the modifier from 115.5 °C to 107.9 °C. [ABSTRACT FROM AUTHOR]

In this paper, transparent intumescent flame retardant coatings were prepared with melamine-formaldehyde resin (MF) as the film-forming resin, phosphoric acid-pentaerythritol (H3PO4 -PER) as the intumescent flame retardant system, and graphene oxide (GO) as the flame retardant co-agent to improve the flame retardant and smoke suppression performance of wood-plastic composites (WPC). Results showed that the coatings had highly transparency, good physical properties, excellent flame retardancy and smoke suppression properties. The addition of GO did not change the physical properties of the coatings, but significantly improved the thermal stability, flame retardancy and smoke suppression properties of the WPC composites. Thermogravimetric analysis (TG) tests showed that the charcoal residue of the coating increased by 11. 0% when 0. 2% GO was added. The simulated large plate burning method showed that the flame resistance time of the coating increased by 75. 0% compared with the control group when 0. 2% GO was added. Cone calorimeter (CONE) combustion test showed that the addition of GO effectively suppressed the heat release and smoke release of the coating. The total heat release and total smoke release of the coating decreased by 35. 6% and 43. 5%, respectively. The flake structure of graphene oxide became cross-linked points after the coating was expanded by heat, which improved the overall mechanical strength and stability of the carbon layer, and then achieved the effect of flame and smoke suppression. [ABSTRACT FROM AUTHOR]

The common, commercial reversible thermochromic (RT) melamine–formaldehyde resin microcapsules containing formaldehyde are very harmful to human health. To address this issue, we successfully prepared a novel formaldehyde-free microcapsule via interfacial polymerization using RT compositions as the core and poly(urethane-urea) (PUU) as the shell. The core material consisted of a color former (crystal violet lactone), a developer (bisphenol AF), and a solvent (methyl stearate). To optimize the synthesis of the microcapsules, an L9 (34) orthogonal design and single-factor experiments were employed to analyze the effects of four factors (N3300-to-L75 shell material mass ratio, core-to-shell material mass ratio, emulsifier concentration, and shear rate during emulsification) on the encapsulation efficiency. The results showed that the optimal parameter values were as follows: a shear rate of 2500 rpm, N3300-to-L75 shell material mass ratio of 1:4, core-to-shell material mass ratio of 11:5, and emulsifier concentration of 3.5%. The influence of the shear rate on the particle size and distribution, surface morphology, dispersibility, and reversible thermochromic properties of the microcapsules was investigated. Furthermore, analyses on the phase-change characteristics, thermal stability, ultraviolet aging, and solvent and acid–base resistances of the microcapsules were conducted systematically. Finally, a reversible thermochromic mark containing the RTPUU microcapsules was designed and fabricated, which could be used against falsification. Moreover, these RTPUU microcapsules can be potentially used for anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

To develop monoammonium phosphate (MAP) as a novel acid source for durable intumescent fire retardants (IFR), MAP microcapsules (MCMAPs) containing MAP as the internal core and melamine-formaldehyde (MF) as the external shell were prepared by in situ polymerization in this study. The influences of synthesis conditions (including reaction temperature, polymerization time, and reaction pH value) on the properties of obtained MCMAPs (MAP content, yield, morphologies, and thermal properties) were then investigated systematically. The morphologies, chemical structures, and thermal properties were characterized by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetry analyzer (TGA). The results show that MAP was well encapsulated by MF resin. No microcapsules are obtained at <55 °C or with polymerization times <1 h. Optimal preparation conditions of reaction temperature, polymerization time, and reaction pH value are 75 °C, 3 h, and 5.5, respectively. Those results provide process reference and theoretical basis for preparing MCMAPs and could promote the application of MAP microcapsules in wood flame-retardant materials. [ABSTRACT FROM AUTHOR]

Even though cure kinetics of melamine–urea–formaldehyde (MUF) resins with low melamine contents (0–20 mass%) and high-temperature curing have been studied, research on the thermal cure kinetics of cold-setting MUF resins with relatively high melamine content (20–40 mass%) is limited. Therefore, this study reports thermal cure kinetics of cold-setting MUF resins synthesized with three melamine contents, using differential scanning calorimetry. A model-fitting method (Kissinger), three model-free kinetic methods (Friedman (FR), Flynn–Wall–Ozawa (FWO), and Kissinger–Akahira–Sunose (KAS)), and a nonlinear isoconversional (or Vyazovkin) method were employed to theoretically estimate the cure kinetics of cold-setting MUF resins with high melamine content. The results of Kissinger analysis provided reliable activation energy (Ea) which was also comparable with those of isoconversional analysis. As the degree of conversion (α) increased, the activation energy (Eα) of MUF resins decreased, regardless of melamine content. However, the activation energy (Ea), isoconversional activation energy (Eα), and the peak temperature (Tp) increased as the melamine content increased. Two methods such as KAS and Vyazovkin methods were reliable in estimating their cure kinetics based on R2 values and cure kinetic parameters. Analysis of the cure kinetics showed that all melamine contents MUF resins followed an nth-order reaction (OR (n > 1)) model. [ABSTRACT FROM AUTHOR]

Wood-based panels are one of the leading materials for frame structures of furniture. The worldwide shortage of wood raw materials necessitates searching for alternative sources to produce panels. Hemp shives are a representative of precisely this type of raw material. They are characterised by low bulk density and high fibre strength. For this study, four types of one-layered panels from hemp shives were fabricated in laboratory conditions, with a resin content of 8, 10, 12, and 14%, respectively. Accordingly, their main physical and mechanical properties were determined and compared to those of particleboards from raw wood material. It was found that the obtained panels from hemp shives have very good mechanical properties, and their high edge screw withdrawal resistance is very promising in terms of applicability for furniture constructions. As a direct result of these findings, the resin content is not recommended to be above 10%. [ABSTRACT FROM AUTHOR]

The possibilities of fabrication and properties of new furan-containing polymers based on 5-hydroxymethylfurfural (5-HMF) and nitrogen-containing co-monomers (urea and melamine) have been studied. Two series of polymers, namely, 5-HMF-melamine and 5-HMF-urea at different ratios of the furan component: melamine (urea) were obtained. The effect of temperature in the range of 80–180 °C on the degree of cross-linking of polymers was studied. The thermostability of polymers was investigated by the TGA method. The polymers were tested for fire resistance according to GOST 28157-89 standard. It is demonstrated that obtained materials show increased heat and fire resistance in comparison to similar urea- and melamine-formaldehyde resins. It is recommended to use the developed polymers as non-combustible heat-insulating materials. [ABSTRACT FROM AUTHOR]

The way to improve the properties (resistance to washing, delamination, and rubbing off) of the PEDOT:PSS coating applied on wool fabric without reduction of its electrical conductivity by introducing a commercially available combination of low formaldehyde content melamine resins into the printing paste is presented in this paper. Primarily, to improve the hydrophilicity and dyeability of wool fabric, the samples were modified using low-pressure nitrogen (N2) gas plasma. Two commercially available PEDOT:PSS dispersions were used to treat wool fabric by the exhaust dyeing and screen printing methods, respectively. Spectrophotometric measurements of the color difference (ΔE*ab) and visual evaluation of woolen fabric dyed and printed with PEDOT:PSS in different shades of the blue color showed that the sample modified with N2 plasma obtained a more intense color compared to the unmodified one. SEM was used to examine the surface morphology and a cross-sectional view of wool fabric that had undergone various modifications. SEM image shows that the dye penetrates deeper into the wool fabric after plasma modification using dyeing and coating methods with a PEDOT:PSS polymer. In addition, with a Tubicoat fixing agent, HT coating looks more homogeneous and uniform. The chemical structure spectra of wool fabrics coated with PEDOT:PSS were investigated using FTIR-ATR characterization. The influence of melamine formaldehyde resins on the electrical properties, resistance to washing, and mechanical effects of PEDOT:PSS treated wool fabric was also evaluated. The resistivity measurement of the samples containing melamine-formaldehyde resins as an additive did not show a significant decrease in electrical conductivity, while the electrical conductivity was maintained after the washing and rubbing test as well. The best results of electrical conductivity for investigated wool fabrics before and after washing and mechanical action were determined for samples subjected to the combined processing–surface modification by low-pressure N2 plasma, dyeing by exhaust with PEDOT:PSS, and coating by the screen-printing method of PEDOT:PSS and a 3 wt.% melamine formaldehyde resins mixture. [ABSTRACT FROM AUTHOR]

Electromagnetic shielding materials with good ductility, low density, and high shielding performance have excellent application prospects in communication and electronics, aerospace, and military industry. Lightweight three‐dimensional porous conductive foam composite with high electrical conductivity and electromagnetic shielding efficiency has been widely concerned in recent years. In this study, we prepared a special physically modified carbonized melamine foam (CMF) by synergistic modification with graphene (GNs) and multi‐walled carbon nanotubes (CNTs). The lightweight CMF composite with a Unique 3D pore structure has been constructed to achieve high efficiency in EMI shielding. Taking advantage of the synergistic effect of few‐layer nanosheets and CNTs in tailored microporous structure, 15 wt% GNs‐CNTs/CMF composite demonstrates low density of 0.03 g/cm3 and high electrical conductivity of 34.0 S/m, resulting in a significant EMI shielding effectiveness as 3840 dB⋅cm2/g. The microporous architecture contributes to multiple reflection losses of electromagnetic waves by introducing multiple interfaces and also improves the construction of conductive paths to deliver outstanding shielding performance. This work illustrates reference significance for the potential application of lightweight EMI shielding materials with target functions. [ABSTRACT FROM AUTHOR]

Melamine-impregnated paper is made by impregnating paper with melamine-formaldehyde resin and can be hot-pressed and laminated onto the surface of wood boards. If the paper has antibacterial activity, it can prevent the spread of indoor bacteria, but impregnated paper with a long-term antibacterial effect has not been proposed. Metal–organic frameworks (MOFs) have been studied as a reservoir of metal ions. In this study, a silver-metal organic framework (Ag-BTC) was synthesized by a green and scalable method at 60 °C (A-60) and at room temperature (A-25). The structure and thermal stability of the Ag-BTC were characterized. Compared with A-25, the structure and particle size distribution of A-60 were more regular and uniform. The thermal stability and the compatibility of Ag-BTC and MF resin were suitable for hot-pressing process. Ag-BTC in the cured impregnated paper exhibited the sustained-release performance of Ag+. The antibacterial ratio of decorated blockboards with 0.10 wt% A-25 to E. coli and S. aureus exceeded 99.99%, reaching Level I antibacterial grade. Compared with A-60-decorated blockboards, the better antibacterial activity of A-25-decorated blockboards was due to the release of more Ag+. This study provides new ideas for the design of antibacterial melamine-impregnated paper. [ABSTRACT FROM AUTHOR]

In this work, Fe–decorated nitrogen–doped carbon nanospheres are prepared for electrochemical monitoring of acetaminophen. Via a direct pyrolysis of the melamine–formaldehyde resin spheres, the well–distributed Fe–NC spheres were obtained. The as–prepared Fe–NC possesses enhanced catalysis towards the redox of acetaminophen for abundant active sites and high–speed charge transfer. The effect of loading Fe species on the electrochemical sensing of acetaminophen is investigated in detail. The synergistic effect of nitrogen doping along with the above–mentioned properties is taken advantage of in the fabrication of electrochemical sensors for the acetaminophen determination. Based on the calibration plot, the limits of detection (LOD) were calculated to be 0.026 μM with a linear range from 0–100 μM. Additionally satisfactory repeatability, stability, and selectivity are obtained. [ABSTRACT FROM AUTHOR]

Plywood is made of wood veneers that are bonded with adhesives such as urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde resins. The plywood made from formaldehyde-based adhesives not only releases formaldehyde but also relies on fossil resources. In this article, we synthesized furan-acetone adducts from lignocellulosic biomass in one pot. The furan-acetone adducts could be directly used as adhesives with the addition of phosphoric acid as a curing catalyst. Particularly, with the addition of 5 wt% diphenylmethane diisocyanate (MDI) as a crosslinking agent, both the wet and dry bonding strength of the plywood prepared from the adhesives could meet the minimum requirement of 0.7 MPa (Chinese National Standard GB/T 9846-2015). The possible adhesion mechanism is that the penetration of furan-acetone adhesives into vessels and cell lumens followed by crosslinking during hot-pressing forms mechanical interlocking at the interface of wood veneers, which provides the main bonding strength of plywood. The findings presented here could provide a new way for the efficient preparation of aldehyde-free green wood adhesives and the value-added utilization of woody biomass. [ABSTRACT FROM AUTHOR]

In the present work, a flexible carbon sponge is experimentally characterized and proposed as an alternative electrode for advanced vanadium redox flow batteries. Such an electrode is prepared via directly carbonizing the commercially‐available and inexpensive melamine formaldehyde resin sponge in argon, to inherit the well‐defined and three‐dimensional bi‐continuous architecture of the melamine sponge with 99.6% porosity and 40 μm average pore size. By applying the carbon sponges as the electrodes, it is demonstrated that the vanadium flow battery at 200 mA cm−2 can yield an energy efficiency of 77.9%, significantly higher than that with commonly‐used graphite felt electrodes (72.9%). After a thermal treatment in air, the energy efficiency of carbon sponge can further be improved to 81.2% at mA cm−2 due to introduction of favorable oxygen containing functionalities. The operating stability with the carbon sponge is proven by a 200 cycling test with minor efficiency decay. [ABSTRACT FROM AUTHOR]

Lithium–sulfur (Li–S) battery with high energy density is attracting more and more attention as a candidate battery for high-energy power supply in the coming new energy era. However, several defects, such as the insulation properties and shuttle effect of sulfur species, greatly hinder its application. Herein, we rationally design a three-dimensional MXene-based aerogel with a surface area of 221 m2 g–1 and use it as a sulfur host and functional separator for Li–S battery. In the preparation strategy of MXene-based aerogel, Ti3C2Tx and melamine–formaldehyde resin are integrated into a three-dimensional interconnected porous network structure. As the sulfur host, MXene-based aerogel-derived sulfur cathode shows a highly reversible specific capacity of 1042 mA h g–1 at 0.1 C, excellent rate capability, and long-term cycling stability. Furthermore, the modified separator made by coating MXene-based aerogel on the commercial separator has been applied to Li–S battery. Compared with MXene modified separator, the rate capability and cycling performance of Li–S battery with the MXene-based aerogel modified separator are largely enhanced. [ABSTRACT FROM AUTHOR]

The transmission of pathogens via surfaces poses a major health problem, particularly in hospital environments. Antimicrobial surfaces can interrupt the path of spread, while photocatalytically active titanium dioxide (TiO2) nanoparticles have emerged as an additive for creating antimicrobial materials. Irradiation of such particles with ultraviolet (UV) light leads to the formation of reactive oxygen species that can inactivate bacteria. The aim of this research was to incorporate TiO2 nanoparticles into a cellulose-reinforced melamine-formaldehyde resin (MF) to obtain a photocatalytic antimicrobial thermoset, to be used, for example, for device enclosures or tableware. To this end, composites of MF with 5, 10, 15, and 20 wt% TiO2 were produced by ultrasonication and hot pressing. The incorporation of TiO2 resulted in a small decrease in tensile strength and little to no decrease in Shore D hardness, but a statistically significant decrease in the water contact angle. After 48 h of UV irradiation, a statistically significant decrease in tensile strength for samples with 0 and 10 wt% TiO2 was measured but with no statistically significant differences in Shore D hardness, although a statistically significant increase in surface hydrophilicity was measured. Accelerated methylene blue (MB) degradation was measured during a further 2.5 h of UV irradiation and MB concentrations of 12% or less could be achieved. Samples containing 0, 10, and 20 wt% TiO2 were investigated for long-term UV stability and antimicrobial activity. Fourier-transform infrared spectroscopy revealed no changes in the chemical structure of the polymer, due to the incorporation of TiO2, but changes were detected after 500 h of irradiation, indicating material degradation. Specimens pre-irradiated with UV for 48 h showed a total reduction in Escherichia coli when exposed to UV irradiation. [ABSTRACT FROM AUTHOR]

The hydrolysis of cured melamine-urea-formaldehyde (MUF) resin leads to the increment of formaldehyde emission of the MUF resin-bond wood boards. To learn the influencing factors on the hydrolytic stability of cure MUF resin, a variety of amino resins (UF resin, MF resin, MUF resin) were synthesized in the laboratory. The amount of formaldehyde liberated and mass loss of cured amino resins were attained after acidic hydrolysis. The branched structure of cured MUF resins with different melamine levels added at different addition stages was characterized by the XRD technology. The relationship between the hydrolytic stability and branched structure of cured MUF resin was disclosed. The TG and DSC curves of MUF and UF resins were obtained by the differential scanning calorimetry (DSC) at the normal pressure. Their DTG curves were obtained by taking the first derivative of TG curves. The DTG curve shows the variation of the mass-loss rate of UF resin and MUF resin with temperature. The results indicate that the hydrolytic stability of cured MUF resin is lower than that of cured UF resin. The melamine decreases the hydrolytic stability of cured MUF resin by increasing the branched degree of cured MUF resin. The melamine added at different stages affects the branching structure of cured MUF resins in different ways. [ABSTRACT FROM AUTHOR]

[Display omitted] • The melamine resin oligomers with good foamability, which contain both vinyl and hydroxymethyl groups in their molecular structure, has been synthesized by using hydroxypropyl acrylate. • There is a good synergistic effect between the hydroxymethyl polycondensation reaction and free radical polymerization reaction during the forming and setting stages from Moli to TMfoam. • The defects like easy brittle breakage, easy powderization and poor toughness of Mfoam were effectively solved by the synergistic effect of double polymerization reaction during foaming process. • The prepared TMfoam has good toughness, strength, intrinsic flame retardancy, thermal insulation and sound insulation capabilities. Melamine resin foam (Mfoam) is a porous heat-cured amino resin material with excellent flame retardancy, thermal insulation, and noise reduction capabilities. However, some fatal shortcomings like easy brittle breakage, easy powderization and poor toughness directly limit its wide application and further development. In this paper, hydroxypropyl acrylate (HPA) was used to participate in the synthesis of melamine resin oligomers (Moli) in order to link the vinyl group to molecular skeleton. As a result, both vinyl and hydroxymethyl active groups are present in Moli which provide Moli with the ability to perform free radical polymerization reaction and polycondensation polymerization reaction, named double polymerization reaction (DPR), and produce synergistic effects to form a structurally toughened melamine resin foam (TMfoam). The research shows that the scheme can effectively solve the problems of brittle breakage and easy powderization of Mfoam. And under apparent density (Ad) of 40 ± 2 kg/m3, the prepared TMfoam has good toughness, with the bending strength of 405.2 kPa, the compression strength of 352.5 kPa, and the pulverization rate of 1.18 %. Meanwhile, the combustion grade of the TMfoam can reach to B 1 grade, and the thermal conductivity is 0.0328 W/(m·K). Also the absorption coefficient of TMfoam can reach up to 0.92 under frequency of 3045 Hz. All the facts indicate that the DPR showed good synergistic effect during the forming and setting stages from Moli to TMfoam. At the same time, the bubble chamber of TMfoam changes from metastable state to stable state, and its strength and toughness are significantly improved in step. This research has great and practical significance for expanding the wide application of Mfoam type materials. [ABSTRACT FROM AUTHOR]

Atmospheric drying method for fabricating aerogels is considered the most promising way for casting aerogels on a large scale. However, the organic solvent exchange, remaining environmental pollution risk, is a crucial step in mitigating the impact of surface tension during the atmospheric drying process, especially for wet gel formed through the alkoxy-derived sol-gel process, such as melamine-formaldehyde resin (MF) aerogel. Herein, a tough polymer-assisted in situ polymerization was proposed to fabricate MF resin aerogel with a combination of mechanical toughness and strength, enabling it to withstand the capillary force during water evaporation. The monolithic MF resin aerogel through the sol-gel method can be directly prepared without additional network strengthening or organic solvent exchange. The resulting MF resin aerogel exhibits a homogeneous as well as hierarchical structure with macropores and mesopores (~6 μm and ~5 nm), high compressive modulus of 31.8 MPa, self-extinguishing property, and high-temperature thermal insulation with 97 % heat decrease for butane flame combustion. This work presents a straightforward and environmentally friendly method for fabricating MF resin aerogels with nanostructures and excellent performance in open conditions, exhibiting various applications. • A tough biomass-assisted in situ polymerization is proposed for the fabrication of melamine-formaldehyde (MF) resin aerogel via the atmospheric drying method. • Benefiting from the robust cross-linking networks and homogeneous porous structures, the MF resin aerogel displayed a modulus of 31.8 MPa. • The MF resin aerogel exhibits superior flame retardance with a limiting oxygen index value of 35.5% and high temperature insulation. [ABSTRACT FROM AUTHOR]

The polyurethane (PU) foams can be functionally tailored by modifying the formulation with different additives. One such additive is melamine (MA) formaldehyde resin for improving their flame-retardant properties. In this work, the glycerol-modified (GMF), sodium alginate (SGMF)- and lignosulfonate-modified melamine formaldehyde (LGMF) were prepared and used as flame retardants reacting with isocyanate to prepare the corresponding rigid polyurethane foams (GMF-PU, SGMF-PU and LGMF-PU). The thermomechanical properties and flame-retardant properties of the foams were characterized. The results showed that the specific compression strength of GMF-PU, SGMF-PU and LGMF-PU increased substantially compared to the foams from physical addition of MA, sodium alginate and lignosulfonate, all of which were greater than that of the foam without any flame retardant (PPU). Meanwhile, the cell wall of the foam pores became thicker and the closed pore ratio increased. The sodium alginate and lignosulfonate played a key role in enhancing foam thermal stability. The limiting oxygen index values and cone calorimetry results indicated the flame-retardant efficiency of GMF-PU, SGMF-PU and LGMF-PU was significantly enhanced relative to PPU. Meanwhile, the heat and smoke release results indicated sodium alginate and lignosulfonate could reduce the amount of smoke generation to different degrees during the combustion of the foam. [Display omitted] • Sodium alginate- and lignosulfonate-modified resins were prepared to realize the high-value utilization of biomass resources. • The bio-based flame-retardant polyurethane foams indicate preferable flame resistance. • The sodium alginate and lignosulfonate could reduce the smoke generation during the foam combustion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu2+ doped molecularly imprinting resin was synthesized with hydrophilic monomers. • Cu-MIR presents special recognition to TCs in environmental water. • Cu-MIR was applied for enrichment of TCs in environmental water with satisfactory recoveries. Antibiotic contamination in environmental waters often occurs at low residue levels, necessitating pre-analysis concentration. To address this, we synthesized a hydrophilic molecularly imprinted resin (MIR) using melamine, urea, and formaldehyde as monomers, with oxytetracycline as the template molecule. Enhanced adsorption efficiency was achieved by doping the resin with Cu2+, which forms stable complexes with oxytetracycline. This Cu2+-doped MIR (Cu-MIR) was employed as a selective adsorbent in solid-phase extraction (SPE) to enrich four tetracycline antibiotics (TCs) from aqueous solutions. The optimized parameters for Cu-MIR in environmental water sample analysis resulted in linear detection ranges from 0.20 to 40 ng/mL, recoveries between 80.2 % to 102.4 %, relative standard deviations ≤ 9.0 %, a detection limit of 0.1 ng/mL, and the enrichment factors were between 4.79–5.13, as determined by HPLC-MS. Given its diverse adsorption mechanisms and specificity, Cu-MIR shows promise for practical applications in real-world sample analysis. [ABSTRACT FROM AUTHOR]

Generally, melamine-formaldehyde resin (MF) has some defects, including poor fluidity, high cross-linking density, high curing shrinkage rate, and a tendency to cause brittle fracture in cured films. These factors pose significant obstacles for the direct application of MF in coatings. In this study, a novel purified palmitoylated melamine (PM) intermediate was synthesized by acylation reaction between equal molar palmitoyl chloride (Pc) and melamine(M), and then mixed with M (with 10% mass substitution of M). The mixture was reacted with formaldehyde, butanol, and polyethylene glycol 400 (PEG400) to prepare palmitoylated melamine-formaldehyde resin (PMF). The prepared PMF displays excellent direct coating ability on various hard substrate surfaces, with a cured coating film surface that is uniform and smooth. In addition, the coating exhibits excellent surface hydrophobic function (with a water contact angle is up to 100°), high light transmittance (with a gloss of 135° and a light transmittance of 95.8%), intrinsic flame retardancy (with a limiting oxygen index is 27.6% and a surface resistance to cigarette burning of 5 grade), self-cleaning properties (hydrophobicity, lipophobicity and lubrication) and other comprehensive properties. The adhesion of the coating (cross cut test) was 0 grade, the impact resistance is 80 mm, the pencil hardness was 8H, the wear resistance of the coating was only 0.02 mg per 100 revolutions (0.02 mg/100r), and the coating surface resistance to chemical contamination (tested with acetone, 10% citric acid solution, and 25% sodium hydroxide solution) was level 5. These advantages of great significance for the expansion of the application field of melamine-formaldehyde resin. • A novel structure of PM was prepared by the acylation reaction of equimolar amounts of palmitoyl chloride and melamine. • Keeping the total amount of M constant, 10% by mass of M was replaced with PM and the mixture was used to prepare PMF resin. • PMF resin exhibits excellent direct coating capabilities on a variety of substrates and surface functionalities. • PMF coating exhibits surface hydrophobic function, high light transmission, flame retardancy and other excellent properties. [ABSTRACT FROM AUTHOR]

Customizing catalysts from the electronic structure, such as spin state, is an effective but challenging strategy for oxygen evolution reaction (OER). Herein, an ultrafine Co–Fe material highly dispersed on nitrogen carbide matrix is fabricated by coordination polymer and self-templating method to scrutinize the impact of spin state of Co on OER through Fe doping. The optimized catalyst shows boosted OER performance, which only requires overpotential of 333 mV at 10 mA cm−2, outperforming other control samples and commercial RuO 2. The elevated local spin states of Co by Fe doping lead to charge transfer acceleration and fast generation of oxygenated intermediates, which is proved to account for the OER elevation. In addition, the long-term stability of Co–Fe material is guaranteed by the strong coordination of Co/Fe to the melamine-formaldehyde resin, which is used to adsorb metal ions, contributing to the high dispersion of active sites during the OER process. [Display omitted] • Fe 0.4 Co 0.6 @NC is fabricated by coordination polymer strategy and self-templating method. • The electronic structure and spin states of Co are elevated by Fe doping. • Untrafine Fe 0.4 Co 0.6 @NC exhibits improved OER activity because of more high-valence Co. • The high dispersion of Fe 0.4 Co 0.6 @NC due to strong chelation ensures long-term stability. [ABSTRACT FROM AUTHOR]

3D hierarchical porous Fe, N‐doped hollow carbon nano‐spheres (Fe−N−C HPNCs) as efficient ORR electrocatalyst were obtained using melamine‐formaldehyde resin (MF) nanospheres as thermal sacrificial hard template to optimize the pore structure and provide nitrogen source to the catalyst. The optimized Fe−N−C HPNCs catalyst exhibited excellent catalytic activity with onset (Eonset) and half‐wave (E1/2) potential (Eonset=1.07 V; E1/2=0.90 V vs. RHE) superior to commercial Pt/C catalyst in 0.1 M KOH solution, and demonstrated excellent stability. When applied as cathode electro‐catalyst in a Zn‐air battery, it produced maximum power density (Pmax) of 127 mW cm−2, which is higher than that of commercial Pt/C (Pmax=119 mW cm−2). It also showed good activity (Eonset=0.89 V; E1/2=0.78 V) in 0.1 M HClO4 electrolyte with significantly enhanced stability (ΔE1/2=−7 mV) relative to the Pt/C catalyst (ΔE1/2=−27 mV). [ABSTRACT FROM AUTHOR]

Sulfonated polymer-based materials, among heterogeneous catalysts, are frequently utilized in chemical transformations due to their outstanding chemical and physical durability. In this regard, a magnetic sulfonated melamine–formaldehyde resin (MSMF) catalyst was successfully prepared from a mixture of sulfonated melamine–formaldehyde and Fe3O4 nanoparticles in two steps. MSMF was used as a heterogeneous catalyst for the one-pot, three-component condensation of benzyl pyrazolyl naphthoquinones in water as a green solvent and 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones. The antimicrobial and antioxidant activities of catalyst, benzyl pyrazolyl naphthoquinones, and 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones were evaluated using agar disk-diffusion and DPPH assays, respectively. The antioxidant activity of the catalyst and 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones was found to be 75% and 90%, respectively. Furthermore, catalyst, benzyl pyrazolyl naphthoquinones, and 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones exhibited antimicrobial activity against Staphylococcus aureus and Escherichia coli. In conclusion, MSMF is a superior catalyst for green chemical processes, owing to its high catalytic activity, stability, and reusability. [ABSTRACT FROM AUTHOR]

The swelling and water uptake of wood can be reduced by impregnation with thermosetting resins, forming a wood-resin composite; research into wood modification with MF resins has increased recently ([3],[4]; Behr et al. 2018; [46]; [49]; [69]; [74]). Keywords: acetylation; dimensional stability; melamine formaldehyde (MF) resin; sorption isotherm; thermal modification; wood modification EN acetylation dimensional stability melamine formaldehyde (MF) resin sorption isotherm thermal modification wood modification 437 450 14 05/09/22 20220501 NES 220501 1 Introduction Wood is an important natural and renewable resource, which has many technical advantages, such as its mechanical strength and stiffness in relation to its weight, processing energy and aesthetic properties. All studied wood modifications provided a high efficiency against interactions between wood and water, whereas more detailed analysis of MF resin modified wood needs more attention, as heat-curing conditions may have a significant effect on the water-related properties, as reported recently in the scientific literature. However, only maple and alder wood specimens provided high quality after acetylation, while further adapted process parameters or a limitation in board width are suggested for the acetylation of a highly unstable wood species like beech. [Extracted from the article]

We developed a molten salts process to prepare Co9S8 nanoparticles (NPs) entrapped, S, N co‐doped carbons. Cobalt chloride was used as the cobalt source. The melamine‐formaldehyde (MF) resin provided the carbon source and nitrogen source, and thiourea provided sulfur source. In addition, common inorganic salts were added as templates to generate pores. The characterization results showed that the prepared materials contained high contents of N, S and Co, and were mesoporous composites. At the same time, the porosity of electrocatalyst depended on the type of salt and the mass ratio of precursor to salt, which further affected the electrocatalytic activity of hydrogen evolution reaction (HER). The best prepared catalyst showed excellent HER performance. The onset overpotential of the catalyst was low (33 mV) and had a small Tafel slope (61.1 mV dec−1), in addition to good stability in alkaline media. [ABSTRACT FROM AUTHOR]

The hierarchical pore structures of porous carbons are significant for their catalytic performances of the oxygen reduction reaction (ORR). The template approach is the typical pore-forming pathway of porous carbons. Generally, the pore-forming templates are individually used to create the mesopores or macropores of carbons. Herein, the nanoscale melamine resin spheres (NMRSs) are employed as the mesopore template and the in situ reduced metallic zinc is functioned as the micropore template to enhance the micropores in the meanwhile. Few report is found to create the mesopores by a template and concurrently to make the micropores by another template within the same carbon material. As a demonstration, the zinc nitrate-containing polydopamine encapsulated NMRSs are pyrolyzed to prepare the hierarchically porous doped carbons with high specific surface area, which exhibit excellent catalytic performances for ORR. This dual pore-making strategy is a powerful tool for the fabrication of high-performance porous carbons. The nanoscale melamine resin spheres are employed as the template of the mesopores and the reduced metallic zinc is functioned as the template of the micropores for porous carbons in the meanwhile. The hierarchical porous carbons are achieved by this dual pore-making strategy, exhibiting excellent catalytic performances for the oxygen reduction reaction. [Display omitted] • The in-situ reduced metal zinc is worked as the micropore template of carbon. • The nanoscale melamine resin spheres are used as the mesopore template of carbon. • This dual pore-forming method can be used to prepare high-performance porous carbon. [ABSTRACT FROM AUTHOR]

Hexamethylol melamine resins (HMM) with low crystallization water content and low viscosity were prepared by inhibiting the condensation polymerization of low hexamethylol melamine. The effects of catalyst, pH, formalde-hyde/melamine ratio, reaction temperature and time on the synthesis parameters of HMM were investigated. The results showed that the sample (HMM8) synthesized with Na2CO3-NaHCO3 as catalyst had the crystallization water content lower than 10%, being with a viscosity of about 0.26 Pa·s. The melting temperature of HMM8/polyvinyl alcohol (PVA) curing system was about 164.3 °C. It was found that the higher the amount of formaldehyde, the greater the hydroxyl methyl bounded to each triazine ring. Compared with the traditional melamine formaldehyde resin which had the crystallization water content of about 20–30%, the production of this resin was expected to reduce the energy consumption of industrial reaction, while the resin with 10% crystallization water content was more conducive to the development of alloying HMM/PVA composite membrane. [ABSTRACT FROM AUTHOR]

Melamine-formaldehyde resins are widely used in the production of various technical and household products. By foaming a special resin, it is possible to obtain various foam plastics, including melamine sponges (MS), which, due to their unusual mesh structure and properties, absorb and wash away contamination quite well and have well-pronounced abrasive characteristics. The area of application of melamine sponges can be significantly expanded by their modification. Radiation-synthesized telomeres of tetrafluoroethylene (TFE) are of considerable interest for MS modification, as they make it possible to create protective hydrophobic coatings on various materials and products. This work presents the results of studies of the MS hydrophobization process, using TFE telomeres, synthesized in acetone and the binary solvent of freon 113 + ammonia. The composition and structure of hydrophobized melamine sponges have been studied by the methods of X-ray photoelectron and Raman spectroscopy, optical and scanning electron microscopy. It is shown that the treatment with tetrafluoroethylene telomere solutions makes it possible to give the initial hydrophilic material a highly hydrophobic state, characterized by a contact angle of wetting of the order of 135°–140°. This treatment significantly improves the performance characteristics and expands the practical application possibilities of melamine sponges. The morphology and composition of the modified samples have been studied. It is shown that the telomere can exist in two different states in the MS spatial network: closely bound and loosely bound fractions. The loosely bound fraction can be removed mechanically, the closely bound fraction remains on the MS surface even after several treatments with solvents, ensuring the stability of the hydrophobic properties of the sponge. [ABSTRACT FROM AUTHOR]

Contemporary urea-formaldehyde (UF) resins with low-molar-ratio contain highly crystalline domains induced by the hydrogen (H) bonds between their linear molecules, which inhibits cross-linking, and results in poor adhesion. In this study, a novel way of controlling the crystallinity of such resins by preventing the formation of H-bonds using multi-reactive melamine during synthesis was reported. FTIR and 1H-NMR spectroscopy confirmed the shifting of the carbonyl (C = O) peak, and N-H signal. XRD patterns revealed the conversion of crystalline to amorphous domains by adding 20% melamine, resulting in a decrease in crystallinity from 52 to 22%. The amorphous UF resins cured faster, have higher molecular weight and cross-linking density, and also followed the autocatalytic reaction model with excellent theoretical fitting. In addition, a 33% increase in adhesion strength, and a 62% reduction in formaldehyde emission was recorded. Hence, the addition of 20% melamine into the UF resins leads to better adhesion and less formaldehyde emission. [ABSTRACT FROM AUTHOR]

Utilizing solar energy for interfacial solar steam generation and wastewater remediation is regarded as one of the sustainable approaches for alleviating clean water shortage. However, it is still a great challenge to comprehend all the requirements of efficient evaporation, salt resistance and wastewater treatment as well as low cost in one evaporator, thus hindering its large-scale practical application. Herein, in this work, an environmentally friendly and low-cost hierarchical porous architecture (APC@TMF) was prepared by assembling potassium citrate activated poplar catkin derived porous carbon (APC) into the porous structure of thermalized melamine formaldehyde resin sponge (TMF) by a simple dipping method. The APC@TMF integrates the advantages of APC and TMF, thus leading to good light absorption, low thermal conductivity, high hydrophilicity and fast water transport. As expected, APC@TMF exhibits a high evaporation flux of 2.28 kg m−2 h−1 with energy conversion efficiency of 96.3 % in seawater, which outperforms TMF, PVA/TMF, PVA/APC and recently reported evaporators. Beyond that, it demonstrates good performance for seawater desalination and wastewater remediation as well as high cost-effectiveness. APC@TMF hierarchical porous architecture, assembled by filling poplar catkin (APC) derived carbon into the porous structure of thermalized melamine formaldehyde resin sponge (TMF), is successfully prepared by a simple dipping method, exhibits outstanding solar-driven interfacial seawater evaporation and wastewater purification performance. [Display omitted] • APC@TMF was prepared by assembling biomass-derived carbon into thermalized sponge. • APC@TMF shows good performance in seawater desalination and wastewater remediation. • The hierarchical porous structure of APC@TMF helps reduce the evaporation enthalpy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multicolor, ultra-long room-temperature phosphorescent polymer materials produced. • Polymer Doping Systems with Flexible Processability. • 3D phosphorescent materials can still exhibit long afterglow after 30 days underwater. • Patterned security labels with full-color dynamic phosphorescence. Room-temperature-phosphorescent (RTP) metal-free organic polymer materials with long-lasting luminescence properties have received considerable attention in the field of optical materials. Herein, we report unique RTP polymeric materials with ultralong-lasting multicolor luminescence prepared using a series of organic phosphorescent guest molecules and melamine formaldehyde resins. Because of facile thermal cross-linking, these materials exhibit a stable multicolor long-lasting afterglow with a maximum phosphorescence lifetime of > 1 s and a maximum phosphorescence emission efficiency of up to 3.4 %. In addition, polymer doping systems with flexible processability were easily printed on 2D substrates and further used as patterned security labels with full-color dynamic phosphorescence. Further, different materials were combined to form a ternary digital encryption system. In addition, although reports on 3D-printed phosphorescent materials are scarce, by using a similar thermoforming method, we successfully prepared a 3D-molding phosphorescent material that can exhibit a satisfactory long-lasting afterglow even after it is kept underwater for 30 days. In conclusion, this work will usher in advancements in the development and application of metal-free polymer-based RTP materials with long-lasting luminescence and 3D printing potential. [ABSTRACT FROM AUTHOR]

In this work, sol-gel method is employed to prepare ZnO nanoparticles with different surface defect states. Simultaneously, the prepolymer solution of melamine resin (MF) is also pre-synthesized. Then the as-prepared ZnO nanoparticles are mixed with prepolymer solution of melamine resin, resulting in the multi-colored solid-state photoluminescence phosphors (ZnO NPs@MF) after heat curing and grinding. The enhanced fluorescence emission is observed for ZnO NPs@MF, which may be due to the local field effect and reduction of non-radiative transitions brought by the dispersion and coating of MF resin. In addition, we have applied blue ZnO NPs@MF phosphors to the white light emitting diodes (LED) device, which preliminarily confirms the possibility of using our synthesized fluorescent powder in the indoor light source. • The ZnO NPs@MF phosphors exhibit multi-colored photoluminescence. • The multi-colored luminescence is derived from various defect energy levels. • The phosphors generate enhanced luminescence mainly due to local field effect. • The b-ZnO NPs@MF phosphors can be applied into the white LED. [ABSTRACT FROM AUTHOR]

It has been shown that structural properties of open porous solids, such as the mean pore size, can be derived from gas pressure-dependent thermal conductivity data. However, a reliable prediction of the total thermal conductivity of a porous sample with complex backbone structure from structural data is not possible, because the degree of coupling of gaseous and solid thermal conduction is hard to estimate. To explore the impact of structural effects, the thermal performance of different model structures, generally characteristic for porous solids (necks, dead ends, tortuosity), was theoretically evaluated by means of finite-difference calculations. As a result, we find that dead ends cause the highest amount of thermal coupling. On the other hand, independent experimental investigations were performed to support the theoretical findings. That means, the gas pressure-dependent thermal conductivities of two sample systems in a nitrogen atmosphere were analyzed: At first, thermal conductivity data for three organic, resorcinol–formaldehyde based aerogels with different structural properties were received from hot-wire measurements. Secondly, the regular cell structure of melamine resin foam was systematically changed by uniaxial compression within a guarded hot plate apparatus prior to determining the resulting thermal conductivity in the direction of compression. Overall, the measured gas pressure-dependent thermal conductivities of both systems indicate that the connectivity of the solid network significantly affects the solid–gas coupling term in porous solids. Both the experimental and theoretical results show that the coupling term decreases with increasing connectivity of the backbone material of a porous solid. [ABSTRACT FROM AUTHOR]

This work focuses on the universal applicability of microencapsulation on core materials. From this point, nine different fragrance oils were selected as core materials, and the corresponding melamine resin shell microcapsules were prepared by a uniform process. According to characterization results, the microencapsulation shows good universality for most core materials, but their encapsulation efficiency (E%, 17.28%‐88.26%), particle size distribution (D50, 9.65‐33.82 μm) and optical micro‐morphology are significantly different. By analysing the influence of the interfacial tension (F), relative dielectric constant (ε), viscosity (τ), density (ρ) and refractive index (n) of the core materials on encapsulation, it was found that the F determines whether the core material is suitable, and f ≥ 1 is the basic condition for the core material to have the value of microencapsulation. Besides, the ε and n both can be used as auxiliary criteria, τ and ρ also influence the microencapsulation process. Based on these data, a "Dimensionless encapsulation number" x=F0.25·ρn‐nH2O/ε0.25·τ0.5 was tentatively established, and the mathematical relation between it and corresponding E% was constructed, which could be applied as a semi‐empirical formula in practical work. [ABSTRACT FROM AUTHOR]

Nitrogen-doped transition metal materials display promising potential as bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Fe/N co-doped three-dimensional (3D) porous graphene (FeN-3D-PG) is prepared via a template method using sodium alginate as the carbon source and low polymerization degree melamine resin as the nitrogen source. The low polymerization degree melamine resin can form complexes with Fe3+ in the aqueous solution and further forms high density Fe-N x active sites during pyrolysis. Meanwhile, the formed 3D porous structure efficiently promotes the uniform distribution of Fe-N x active sites. The FeN-3D-PG catalyst exhibits pH-independent ORR activity. For OER, the catalyst possesses a low over potential (370 mV at 10 mA cm−2) in alkaline electrolyte. The Zn-air batteries (ZABs) using FeN-3D-PG as cathode exhibits a power density up to 212 mW cm−2, a high specific capacity of 651 mAh g−1, and the charge-discharge stability of 80 h. This work provides new sight to transition metal materials based ZABs with excellent performance. • FeN-3D-PG electrocatalysts are prepared using green synthesis procedure. • The sodium alginate extracted from algae belongs to cheap green materials. • FeN-3D-PG catalyst possess high density FeN x actives and bifunctional performance. • The ZABs using FeN-3D-PG-4 as cathode exhibit excellent charge-discharge performance. [ABSTRACT FROM AUTHOR]

The wide application of melamine–formaldehyde resins (MFRs) in the food industry aggravates plastic pollution problems. Recycling of the waste MFRs remains a big challenge due to its compact structure. Herein, a high MFR degradation ratio of ca. 84 wt% was achieved under mild conditions (180 °C) in a methanesulfonic acid (MSA)–tetrahydrofuran (THF)–H2O system with cyanuric acid as the main degradation product. The SEM results showed that the degradation of MFRs followed different reaction mechanisms when H2O and THF were applied as solvents, respectively. The combination of the two solvents showed an obvious synergistic effect for the degradation of MFRs. The degradation experimental results with melamine as the model intermediate indicated that the degradation of MFRs proceeded via the selective cleavage of the sp2C–sp3N and sp3C–sp3N bonds to recover valuable C and N alternated-aromatic ring (CNAR) units, followed by their transformation into a valuable chemical of cyanuric acid. [ABSTRACT FROM AUTHOR]

An aqueous emulsion polymerization self‐assembly approach is demonstrated for the first time to synthesize ultrahigh nitrogen containing mesoporous polymer nanospheres, using melamine‐formaldehyde resin oligomers as precursors. In the synthesis, change from alkaline to acidic conditions is critical for the formation of monodisperse mesostructured polymer nanospheres. Owing to unique structure of triazine stabilized in the covalent polymeric networks during the pyrolysis process, the derived mesoporous carbon nanospheres possess an ultrahigh nitrogen content (up to 15.6 wt%) even after pyrolysis at 800 °C, which is the highest nitrogen content among mesoporous carbon nanospheres. Furthermore, these monodisperse mesoporous carbon nanospheres possess a high surface area (≈883 m2 g−1) and large pore size (≈8.1 nm). As an anode for sodium‐ion batteries, the ultrahigh nitrogen‐containing mesoporous carbon nanospheres exhibit superior rate capability (117 mAh g−1 at a high current density of 3 A g−1) and high reversible capacity (373 mAh g−1 at 0.06 A g−1), indicating a promising material for energy storage. [ABSTRACT FROM AUTHOR]

Melamine formaldehyde (MF) resin is a thermosetting polymer with superior flame retardancy and high thermal stability and is widely used in fire-retardant coatings, flame-retardant sheets, heat-resistant filter materials, and so on. However, its further application is restricted by its extreme brittleness and poor impact strength. In this article, polyvinyl alcohol (PVA), a water-soluble polymer with high toughness and elasticity, which can be well blended with MF prepolymer in hot water, was used to improve the toughness of MF resin. The nano-silicon dioxide (SiO2) particles modified by KH-550 were used to improve the compatibility between MF prepolymer and PVA. Moreover, the modified nano-SiO2 can simultaneously enhance the toughness and impact the strength of MF resin. The interaction of components, fractography, thermal stability, flame retardancy, and mechanical properties of the modified MF resin was studied systematically. Fourier transform infrared results indicate that KH-550 was successfully grafted onto the surface of nano-SiO2. The grafted nano-SiO2 shows better dispersion in the matrix than the unmodified one, furthermore improving the compatibility and interface adhesion between MF and PVA. When PVA content is 20%, the obtained material has good thermal stability (Tmax > 350°C), flameretardant properties (UL-94 V-0 rating and limited oxygen index = 42%), and toughness (elongation at break > 20% and unnotched impact strength > 13 kJ m-2). [ABSTRACT FROM AUTHOR]

Polymer nanocomposite films were formed from the aqueous dispersion of thermally linking styrene-acrylic copolymer (Tubifast 4010®, CHT), partially esterified melamine resin (Tubifix®, CHT), and ZnO nanoparticles as filler. The developed nanocomposite films were characterized by elemental (CHNS) analysis, SEM, EDX, IR spectroscopy, XRD, and swelling degree study. The EDX analysis proved the presence of Zn in the polymer nanocomposite, and according to SEM and XRD, all ZnO nanoparticles are separated with a uniform structure with 20 nm in size. Analyzing a swelling degree of the polymer films showed that the film with nano ZnO as the filler possesses 3.4 times lower swelling degree compared to the film formed from Tubifast 4010®. This can be explained by the inorganic structure of ZnO and the ability to form extra chains, which is consistent with IR spectroscopy data. It was demonstrated that the polymer nanocomposite film could adsorb methylene blue due to the quick swelling of the film which increases the volume of the sample and provides more active adsorption sites of the film. [ABSTRACT FROM AUTHOR]

• A melamine resin-cobalt@piperazine pyrophosphate microcapsule was prepared. • Flame retardancy and mechanical performance of RPUF was improved with MF-Co@PAPP. • Smoke suppression achieved by the synergic effect of the components of MF-Co@PAPP. • Microcapsule structure of MF-Co@PAPP imparts long-lasting fire safety to RPUF. The persistent challenge of maintaining fire safety in flame retardant modified rigid polyurethane foams (RPUF) under humid conditions continues to be a concern. To address this challenge, a microcapsule named MF-Co@PAPP has synthesized, composed of melamine resin (MF, shell) and piperazine pyrophosphate (PAPP, core). This microcapsule was developed to enhance the long-lasting flame retardancy and smoke suppression of RPUF. These composites demonstrated a significant reduction in total heat release and total smoke release compared to pure samples, with decreases of 44% and 29%, respectively. The MF-Co@PAPP facilitated the carbonization process of RPUF, leading to the formation of a more stable char layer. The RPUF/MF-Co@PAPP composites exhibited the highest limiting oxygen index values, even after a 14-day immersion in water. This study introduces a target-driven design approach to enhance the fire safety of RPUF, offering inspiration for future development of tailored flame retardants. [Display omitted] [ABSTRACT FROM AUTHOR]

Melamine formaldehyde resin (MF) has a long history of about 90 years since its birth. Its industrial application, however, has been limited by the high cost of raw materials, high content of free formaldehyde and easy cracking of adhesive layer after curing. These problems can be solved by making use of biomass resources to modify MF in theory. Sucrose, melamine and formaldehyde were noted as the main raw materials for synthesizing sucrose-melamine-formaldehyde copolymer resin (SMF) under alkaline conditions. The effect of sucrose content and curing agent on the curing properties have been carried out through Fourier transform-infrared spectroscopy (FT-IR), nuclear magnetic resonance spectrum (NMR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The findings show that the SMF curing behavior was an exothermic process, which was achieved by the dehydration synthesis between hydroxymethyl groups. The sucrose content had a large effect on the thermal stability and the curing behavior of SMF, and the addition of curing agent promoted the resin curing. Not only was the thermal stability decreased, but also the curing reaction was more difficult to occur with the sucrose addition. The sucrose molecules participated in the curing process through chemical bonding, and then formed a stable network structure for the resin system. [ABSTRACT FROM AUTHOR]

In this paper, a melamine formaldehyde resin modified with tris(2-hydroxyethyl) isocyanurate (THEIC), named MF-THEIC, was synthesized via a solid-phase reaction between hexahydroxymethyl melamine (HMM) and THEIC. MF-THEIC was firstly used as a charring agent in an intumescent flame-retardant system together with APP as well as 4A-zeolite in flame-retarding PP. APP/MF-THEIC (3/1) can effectively reinforce the flame retardancy of PP at a total 24.0 % additive amount, moreover, 1.5 % 4A-zeolite is sufficient to achieve an optimum synergistic effect. The corresponding composites (Sample-17) had passed UL-94 V-0 classification well. The synergistic flame-retarding mechanism was systematically investigated by SEM, 31P NMR, TGA, FTIR spectra, and TG-MS. 4A-zeolite can react with APP to generate highly-active phosphates with good catalytic efficacy on polyphosphate esterification, and then to promote the formation of the char layer, simultaneously, 4A-zeolite is helpful to enhance the char graphitization degree and the strength of the intumescing char layer, thereby reinforcing its flame retardancy via a synergistic effect. • A novel charring agent MF-THEIC was synthesized via a solid phase reaction between HMM and THEIC. • APP/MF-THEIC promoted the charring due to the chemical reactions. • 1.5 % 4A-zeolite synergistically improved the flame retardancy with APP/MF-THEIC in PP. • 4A-zeolite increased the graphitization degree and the strength of the intumescing char layer. [ABSTRACT FROM AUTHOR]