Sponge-nested polymer monoliths: Versatile materials for the solid-phase extraction of bisphenols

Polymer monoliths are promising materials for sample preparation due to their high porosity, pH stability, and simple preparation. The use of melamine formaldehyde foams has been reported as an effective support to prepare highly robust silica and polymer monoliths. Herein, divinylbenzene monoliths based on a 50:50 (%, w/w) crosslinker/porogen ratio have been nested within a melamine-formaldehyde sponge, resulting in monoliths with a surface area higher than 400 m²/g. The extraction performance of these monoliths was evaluated for the extraction of endocrine-disrupting bisphenols from aqueous solutions. We evaluated for the first time the versatility of sponge-nested polymer monoliths by comparing three different extraction modes (vortex mixing, magnetic stirring, and orbital shaking). Vortex mixing showed a comparable recovery of bisphenols (39%–81%) in a shorter extraction time (30 min, instead of 2 h). In addition, the robustness of the sponge-nested polymer monoliths was demonstrated for the first time by reshaping a larger monolithic cube (0.125 cm³) into four smaller pieces (4 × 0.03125 cm³) leading to a 16%–21% increase in extraction efficiency. This effect was attributed to an increase in the effective contact area with the sample, obtaining a higher analyte extraction capacity.     

锰氧化物/碳氮三维网络结构复合材料的制备及锂电性能

通过硝酸锰和乙醇的水热反应在三聚氰胺泡棉(MF)上生成三氧化二锰颗粒,氮气下高温处理后形成锰氧化物负载碳氮三维网络结构的复合物。碳氮网络结构提高了充放电过程中材料结构的稳定性及导电性,且烧结过程中产生的孔道结构有利于锂离子传输,使得该复合材料作为负极在锂离子电池中表现出优异的充放电性能和循环稳定性。材料的比容量和循环稳定性大大提高,经500℃处理后的MnO/CNnws-500材料在160次循环后仍然保留590 m Ah·g~(-1)的比容量,达到氧化亚锰理论容量755 m Ah·g~(-1)的78%。     

A new approach on improving the fire resistance of polyamide 11 by incorporating sulfur‐based flame retardant

In this work, a novel sulfur‐based flame retardant (SA‐M) was synthesized by the self‐assembly of melamine and sulfamic acid. The chemical structure of SA‐M was fully characterized. SA‐M, in company with Al₂O₃, was then introduced into polyamide 11 (PA 11) by melt compounding in order to improve the fire resistance of the polymer substrate. The observation by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) indicated the well dispersion of SA‐M in PA 11 matrix. The fire performance of PA 11 composites was evaluated by limiting oxygen index (LOI), vertical burning (UL‐94), and cone calorimeter tests, respectively. The results showed that the presence of 17.5% SA‐M and 2.5% Al₂O₃ increased the LOI value from 22.4% to 30.9%, upgraded the UL‐94 rating from no rating to V‐0, significantly eliminated the melt dripping, and decreased the peak heat release rate from 1024 to 603 kW/m². The thermal behaviors were investigated by thermogravimeric analysis (TGA) and TGA‐Fourier transform infrared spectroscopy (FTIR). It was suggested that SA‐M took effects mainly in gas phase by diluting the combustible fuel, leading to the improvement of the fire resistance of PA 11.     

Highly Elastic Melamine Graphene/MWNT Hybrid Sponge for Sensor Applications

The rapidly increased interest in multifunctional nanoelectronic devices, such as wearable monitors, smart robots, and electronic skin, motivated many researchers toward the development of several kinds of sensors in recent years. Flexibility, stability, sensitivity, and low cost are the most important demands for exploiting stretchable or compressible strain sensors. This article describes the formation and characteristics of a flexible, low-cost strain sensor by combining a commercial melamine sponge and a graphene/carbon nanotubes hybrid. The composite that emerged by doping the highly elastic melamine sponge with a highly conductive graphene/carbon nanotubes hybrid showed excellent piezoresistive behavior, with low resistivity of 22 kΩ m. Its function as a piezoresistive material exhibited a high sensitivity of 0.050 kPa⁻¹ that combined with a wide detection area ranging between 0 to 50 kPa.     

三聚氰胺热解产物的特性分析

以有机物三聚氰胺为初始原料, 在真空条件下使其热解（1 000 K）. 采用X射线衍射（XRD）、 透射电子显微镜（TEM）、 X射线光电子能谱(XPS)、 化学元素分析（EA）和傅里叶红外光谱(FT-IR) 分析样品的形貌、 成分和结构. 结果表明, 在真空条件下, 三聚氰胺全部分解, 分解产物为片层石墨相C₃N₄.      

聚磷酸三聚氰胺的合成与分析

采用溶剂法合成聚磷酸三聚氰胺,考察了反应温度、反应时间、原料物质的量比等条件对反应的影响,确定了聚磷酸三聚氰胺的最佳合成工艺,并对其磷含量及热失重进行了分析测定。     

汽车罩光清漆的固化和降解机理研究(Ⅱ)--用色谱质谱,核磁共振和红外光谱等方法研究罩光清漆的主要成分和结构

罩光清漆的色谱质谱(GC/MS),13C,1H液体高分辨核磁共振(NMR)和红外光谱(IR)等多种方法的综合分析结果表明,新型汽车涂料主要是由丙烯酸丁酯,丙烯酸1,2-丙二醇酯等形成的丙烯酸酯共聚物和部分丁氧基化的三聚氰胺甲醛树酯交联剂所组成,它们溶解在由多种有机溶剂组成的混合溶剂中.     

π-π interactions in the self-assembly of melamine and barbituric acid derivatives

Self-assembly of a pair of complementary molecular components, 5-(4-dodecyloxyben-zylidene)-(1H,3H)-2, 4,6-pyrimidinetrione (PB₁₂)and 4-amino-2,6-didodecylamino-1, 3, 5-triazine (M₁₂) was studied by cyclic voltammogram, surface photovoltage spectroscopy, fluorescence spectroscopy, FTIR and X-ray diffraction. It is found that after mixing equimolar amount of PB₁₂ and M₁₂ at room temperature, not only triply complementary hydrogen bonds are formed between PB₁₂and M₁₂ but also further self-assembly of the supermolecules based on network of hydrogen bonds occurs via π-π interactions. During the self-assembly of the supermolecules, π -π interactions are induced by delocalized interactions between the HOMO of M₁₂ and the LUMO of PB₁₂, resulting in the formation of a supramolecular nanotube with a layered structure bearing a d value of 0.41 nm and PB₁₂ and M₁₂are arranged alternatively between adjacent supermolecules.     

Advances on melamine determination by micellar liquid chromatography: A review

Melamine is a toxic triazine which has been recently proven as a threat to human health. It can be ingested by several methods, being the most important the unethical adulteration of protein-rich foodstuff for economic reasons. This review presents several analytical methods, taken from the literature studies, devoted to the determination of melamine in milk, dietetic supplements, drinking and wastewater, swine kidney, plasma, and urine, using micellar liquid chromatography (MLC). We consider that the control of these samples is crucial to prevent and manage melamine intoxication. This technique has been demonstrated as an excellent tool to determine organic compounds in these matrices. We detail the optimization strategy and the obtained results in the different steps of method development, such as sample pretreatment, chromatographic separation, and validation process. The similarities and differences of the procedures have been described and discussed, as well as their advantages. The main ones were the possibility of direct injection and the efficient chromatographic elution, in spite of the complexity of the samples. Besides, it was found that the MLC procedures were fast, easy-to-handle, inexpensive, eco-friendly, safe, and useful for routine analysis. Therefore, they represent an excellent alternative to reliably evaluate the melamine concentration in that kind of samples.