Zinc Hydroxystannate/Carbon Nanotube Hybrids as Flame Retardant and Smoke Suppressant for Epoxy Resins.

Novel hybrid flame retardants containing zinc hydroxystannate and carbon nanotubes (ZHS-CNTs) were synthesized using the coprecipitation method, and the structure and morphology of ZHS-CNTs were investigate using an X-ray powder diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and thermogravimetric analyzer (TGA). Then, the ZHS, CNTs and ZHS-CNTs were incorporated into EP, respectively, and the flame-retardant and smoke inhibition performance of the composites were compared and studied. Among the three composites, the EP/ZHS-CNT composites have the highest improvements on the fire resistance and smoke inhibition properties. With only 2.0 wt.% ZHS-CNT hybrids, the pHRR of EP/ZHS-CNT composite materials is reduced by 34.2% compared with EP. Moreover, the release of toxic gases including CO, CO2 and SPR from the composites was also effectively inhibited. The mechanisms of flame retardant and smoke inhibition were investigated and the improved properties were generally ascribed to the synergistic flame-retardant effects between ZHS and CNTs, the catalyzing effect of ZHS and the stable network structure of CNTs.

Magnetization of amorphous FeOOH chrysanthemum-like nanosheets under ambient conditions.

The conversion of paramagnetic solid iron oxides to magnetic iron oxides has drawn considerable interest, but it's still challenging to carry out without heat treatment or irradiation. In this work, solid amorphous iron oxide chrysanthemum-like nanosheets synthesized by a smart redox strategy at the interface of a soap-free emulsion are magnetized at room temperature and under ambient pressure. An amorphous FeOOH hollow shell with needles towards water is produced by the reaction of cumyl hydroperoxide (CHPO) and iron(II) sulfate (FeSO4) at the interface of the emulsion generated by ultrasound and torn up into chrysanthemum-like nanosheets simultaneously. With the presence of noble metal ions, such as Au3+, the magnetization of the nanosheets was carried out as soon as sodium borohydride (NaBH4) was introduced into the dispersion. The magnetic chrysanthemum-like nanosheets present saturation magnetization (Ms) of 32 emu g-1 and can be placed linearly in a magnetic field.

Obesity Metabolic Phenotype, Changes in Time and Risk of Diabetes Mellitus in an Observational Prospective Study on General Population.

Objectives: To evaluate the distribution and changes in different obesity metabolic phenotypes, as well as their impact on the incidence of type 2 diabetes mellitus (T2DM) in a northwest Chinese population sample. Methods: Data comes from prospective cohort study (n = 1,393, mean follow up = 9.46 years). Participants were classified into four groups through a combination of the Chinese Diabetes Society (CDS) diagnostic criteria for metabolic syndrome with anthropometric measurements: metabolically healthy normal weight (MHNW), metabolically healthy overweight/obese (MHO), metabolically unhealthy normal weight (MUNW), and metabolically unhealthy overweight/obese (MUO). Cox regression models with time-dependent covariates were used to evaluate changes in obesity metabolic phenotypes and risk of T2DM. Results: Participants in MUO state had the highest risk of developing T2DM, the incidence density was 12.10/1,000 person-year. The MHO and MUO groups showed an increased risk of incident diabetes based on body mass index (BMI) (HR, 1.29; 95% CI, 1.03-1.61; p = 0.026 and HR, 1.20; 95% CI, 1.02-1.40; p = 0.024 respectively.) Besides, the MHO group had an increased risk of incident diabetes based on waist circumference (WC) (HR, 1.41; 95% CI, 1.10-1.80; p = 0.006). Conclusion: Diabetes is more frequent in the MHO and MUO groups and co-occurrence of obesity and metabolic abnormalities (MA) contributes to the development of T2DM.

Metal-organic Framework ZIF-67 Functionalized MXene for Enhancing the Fire Safety of Thermoplastic Polyurethanes.

In this work, a novel functionalization strategy for ZIF-67-modified layered MXene was proposed, aiming at improving the fire safety of thermoplastic polyurethanes (TPU). The ZIF-67@MXene was verified by microscopic morphology, elemental composition, functional group species and crystal structure, and then the successfully prepared ZIF-67@MXene was introduced into the TPU material. When ZIF-67@MXene content was only 0.5 wt%, the peak heat release rate, total heat release rate, peak smoke release rate, total smoke release rate, and CO yield of the TPU/ZIF-67@MXene composites were reduced by 26%, 9%, 50%, and 22%, respectively, compared with the pure TPU. The thermogravimetric tests showed that the residual char of TPU/ZIF-67@MXene composites was the most in all samples. In short, the high-quality carbon layer of TPU/ZIF-67@MXene composites acts as a physical barrier to the transfer of heat and toxic gases, greatly improving the flame retardant properties of the TPU polymer.

Recent Advances in the Synthesis and Application of Three-Dimensional Graphene-Based Aerogels.

Three-dimensional graphene-based aerogels (3D GAs), combining the intrinsic properties of graphene and 3D porous structure, have attracted increasing research interest in varied fields with potential application. Some related reviews focusing on applications in photoredox catalysis, biomedicine, energy storage, supercapacitor or other single aspect have provided valuable insights into the current status of Gas. However, systematic reviews concentrating on the diverse applications of 3D GAs are still scarce. Herein, we intend to afford a comprehensive summary to the recent progress in the preparation method (template-free and template-directed method) summarized in Preparation Strategies and the application fields (absorbent, anode material, mechanical device, fire-warning material and catalyst) illustrated in Application of 3D GAs with varied morphologies, structures, and properties. Meanwhile, some unsettled issues, existing challenges, and potential opportunities have also been proposed in Future Perspectives to spur further research interest into synthesizing finer 3D GAs and exploring wider and closer practical applications.

DOPO/Silicon/CNT Nanohybrid Flame Retardants: Toward Improving the Fire Safety of Epoxy Resins.

Novel DOPO/silicon/CNT nanohybrid flame retardants (FR-CNTs) were synthesized and FR-CNTs were introduced into epoxy resins through thermal curing process. The SEM and TEM results indicate that CNTs distribute uniformly in epoxy resins due to the good dispersion of CNTs in DOPO/silicon/CNT nanohybrid flame retardants. The thermal stability and flame-retardant properties of EP/FR-CNTs composites are improved, which is attributed to the good dispersion of DOPO/silicon/CNT nanohybrid. The cone calorimeter results demonstrate that FR-CNTs can reduce peak heat release and the release of toxic gas effectively compared with EP/CNTs and EP/CNT/FR composites. The char-residue analysis indicates that the improved flame-retardant properties are due to the char-reinforcing effects and the catalyzing charring effect of FR-CNTs, which provides enough time for flame retardants to trap radicals. Generally, the char layers, which act as insulating barrier, can reduce the releasing of flammable gases and protect the underlying epoxy resins from the heat source.

Reusable Magnetic Nanoparticle Immobilized Nitrogen-Containing Ligand for Classified and Easy Recovery of Heavy Metal Ions.

Functionalized Tris[2-(dimethylamino) ethyl] amine (Me6TREN) ligands tethered-Fe3O4@Me6TREN nanoparticles (NPs) with a size of 150 nm were prepared to achieve classified and easy recovery of heavy metal ions in wastewater. The preparation of such NPs related to sequential silane ligand exchange and a following cure and Schiff base reactions for Fe3O4 NPs. Fe3O4@Me6TREN NPs as an effective nano-adsorbent of heavy metals exhibited significant differences in maximum adsorption capacity for Cr(III) (61.4 mg/g), Cu(II) (245.0 mg/g), Pb(II) (5.3 mg/g), and Cd(II) (1136.2 mg/g), in favor of classified removal of heavy metals from wastewater. Furthermore, Fe3O4@Me6TREN NPs can be regenerated by desorbing metal ions from NP surfaces eluted with ethylenediaminetetraacetic acid disodium salt (EDTA-Na2) aqueous, which endows such NPs promising potency as new nano-vectors for the removal of heavy metals.

CNT modified layered α-MnO2 hybrid flame retardants: preparation and their performance in the flame retardancy of epoxy resins.

In this paper, CNT modified layered α-MnO2 hybrid flame retardants (α-MnO2-CNTs) were synthesized through one-pot preparation. The structure and composition of the α-MnO2-CNTs hybrid flame retardants were investigated by X-ray diffraction, TEM and SEM. Subsequently, the α-MnO2-CNTs hybrids were then incorporated into epoxy resin (EP) to improve the fire safety properties. Compared with pure EP and the composites with CNTs or α-MnO2, EP/α-MnO2-CNTs composites exhibited improved flame retardancy and smoke suppression properties. With the incorporation of only 2.0 wt% of α-MnO2-CNTs hybrid flame retardants, the peak heat release rate and total heat release of the composites showed 34% and 10.7% reduction respectively. In addition, the volatile gases such as CO and CO2 were reduced and the smoke generation was also effectively inhibited. The improved fire safety of the composites is generally due to the network structures and the synergistic effect of α-MnO2 and CNTs, the catalyzing charring effect, smoke suppression and the physical barrier effect of α-MnO2 nanosheets.

Functionalized CNTs with DOPO and Silicon Containing Agents: Effective Reinforcer for Thermal and Flame Retardant Properties of Polystyrene Nanocomposites.

DOPO and silicon containing agents modified multiwalled carbon nanotubes (MCNTs) were synthesized through sol-gel process and MCNTs are introduced into polystyrene (PS) through in situ polymerization. TEM observations and FTIR results of MCNTs demonstrated that the MCNT nanofillers were coated with the organic/inorganic flame retardant compound. Moreover, the TEM results of the composites indicate that MCNTs dispersed in polystyrene PS matrix uniformly due to the modification. The PS/MCNTs composites showed improved thermal stability as well as flame retardant properties in comparison with PS/CNTs composites, which are due to the good dispersion of MCNT in the PS matrix. MCNTs in the PS matrix can also reduce the peak heat release rate, total heat release and improve the smoke suppression performance. The improved flame retardant properties are attributed to the char reinforcing effect of CNTs, which can provide enough time for MCNTs and organic/inorganic compound to trap the degradation of polymer chains and catalyze the formation of char. The char layers can not only serve as an efficient insulating barrier to reduce the exposure of PS matrix to heat source but also retard the releasing of combustible gas.

Bottlebrush-Colloid Janus Nanoparticles.

A bottlebrush-colloid Janus nanoparticle (JNP) with a ball-and-stick structure is reported. A single poly(4-vinyl benzyl chloride) (PVBC) polymer chain was grafted onto the amine-capped Fe3O4@NH2 nanoparticle. pH-responsive 2-diethylaminoethyl methacrylate (DEAEMA) and water-soluble oligo(ethylene glycol) methacrylate (OEGMA) were sequentially grown from the PVBC backbone by ATRP, forming a core-shell bottlebrush. The synthesized PVBC208-g-(PDEAEMA13-b-POEGMA8)-Fe3O4@NH2 JNPs are dispersible in water and can be manipulated by a magnet. The Fe3O4 NPs with exposed -NH2 groups facilitate accumulation at acidic sites. Hydrophobic dyes can be loaded within the PDEAEMA at pH ≥ 7.5, while they are released at pH values below 6.8. The composite JNPs are promising as a guided pH-responsive delivery vector toward acidic solid tumors.