Search

In order to apply the rigid biodegradable PLA material for flexible toothbrush bristle products, in this paper, Poly(lactic acid) (PLA) and thermoplastic polyurethane elastomer (TPU) blends (TPU/PLA composites), with a mass ratio of 80:20, were prepared by the melt-blending method to achieve toughening modification. Infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and low-field nuclear magnetic resonance were used to investigate the effect of the compatibilizer, Maleic anhydride grafted polypropylene (PP-g-MAH), on the compatibility of the blends, and the effect of melamine on the flame retardant properties of the blends was further investigated. The results demonstrated that 3% PP-g-MAH had the best compatibility effect on PLA and TPU; the TPU/PLA composites have a better macromolecular motility and higher crystallization capacity in the amorphous regions through the physical and chemical action by using PP-g-MAH as a compatibilizer. By adding melamine as a flame retardant, the scorch wire ignition temperature of TPU/PLA composites can reach 830 °C, which was elevated by 80 °C compared with pure PLA; however, the flame retardant effect of melamine in a single system was not significant. Melamine acts as a flame retardant by absorbing heat through decomposition and diluting the combustible material by producing an inert gas.

In this paper, novel flower-like hollow MoS2 microspheres (FHMs) were synthesized by a hydrothermal method using MF microspheres as template. The FHMs were hydrophobically modified and utilized as porous fillers to fabricate FHMs/acrylic resin composites through suspension polymerization. The oil-absorption tests revealed that the composite with 4 wt% FHMs had a high oil-absorption capacity, which might be due to the synergistic absorption effect of organic and inorganic components. Their high absorption capacity, rapid absorption rate, and excellent reusability make them attractive options as absorbents for practical oil/water separation.

The supported graphitic-carbon nitride (g-C3N4)/Au composite has attracted considerable attention as an alternative visible-light photocatalyst for hydrogen evolution reactions. However, the short-term photocatalytic durability greatly limits their practical application. In this work, porous [Zn(BDC)(H2O)2] n , which is a typical two-dimensional metal–organic frameworks (MOFs), was used as the protecting material to encapsulate g-C3N4/Au. The obtained g-C3N4/Au@[Zn(BDC)(H2O)2] n catalyst was composed of lamellar MOFs shells and g-C3N4/Au cores. The catalysts exhibited an excellent catalytic activity and particularly superior stability as compared to the bare g-C3N4/Au. The encapsulation method by using MOFs as the protective shell provides an alternative strategy for designing photocatalysts with high catalytic performance.

Novel TiO2/Ag/SnO2 composites were successfully prepared by a facile one-step reduction approach using stannous chloride as both SnO2 precursor and reducing agent. The Ag nanoparticles with sizes of 2.04–3.94 nm were located on TiO2 matrix and immobilized by the surrounded SnO2. The resulted TiO2/Ag/SnO2 nanocomposites were used as photocatalyst for photodegradation of methylene blue under visible light. The experimental results demonstrated that the visible light photocatalytic activity of the TiO2/Ag/SnO2 was significantly enhanced in comparison with the individual TiO2 or the binary composite (TiO2/Ag or TiO2/SnO2) and the degradation rate was up to about 9.5 times that of commercial TiO2. The photocatalytic activity of the TiO2/Ag/SnO2 composites could be well controlled by simply tuning the dosages of Ag precursor and the optimized activity of the composites was obtained when the dosage of Ag precursor was 2%. Moreover, the TiO2/Ag/SnO2 photocatalyst exhibited high stability for degradation of methylene blue even after four successive cycles.

In this work, two series of novel high-nitrogen tetrazole 3-N-oxides substituted by different nitrotetrazoles were designed, and their structure and properties were investigated by using the density functional theory (DFT) method. The results shown that though there are only one to two energetic substituents in the structure, because of the high nitrogen content, ideal oxygen balance, and the big conjugated structure, all eight designed compounds not only have high heat of formation (655.4–845.6 kJ/mol), high density (1.83–1.93 g/cm3), and high detonation performance (detonation velocity: 9.06–9.50 km/s; detonation pressure: 36.7–41.8 GPa), but also possess reduced impact sensitivity (23–98 cm). Fully analyzing the energy and sensitivity, A1 and A4 have higher energy and lower sensitivity than one famous high energy compound 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), and A3, B1, and B4 have comparable overall performance with HMX, showing that these five designed compounds may be considered as the potential high energy density compounds. In addition, the introduction of one extra nitro group into the tetrazole 3-N-oxide could not improve the combination property generally.

Based on the parent tetrazole 2N-oxide, six series of novel carbon-linked ditetrazole 2N-oxides with different energetic substituent groups (-NH2, -N3, -NO2, NF2, -NHNO2) and energetic bridge groups (-CH2-, -CH2−CH2-, -NH-, -N=N-, -NH−NH-) were designed. The overall performance and the effects of different energetic substituent groups and energetic bridge groups on the performance were investigated by density functional theory and electrostatic potential methods. The results showed that most of designed compounds have oxygen balance around zero, high heats of formation, high density, high energy, and acceptable sensitivity, indicating that tetrazole N-oxide is a useful parent energetic compound employed for obtaining high energy compounds, even only combined with some very common energetic substituent groups and bridge groups. Comprehensively considering the effects on energy and sensitivity, the -NO2, -NF2, -NH- and -NH−NH- are appropriate substituent groups for combining tetrozale N-oxide to design new ...

A new powerful zero-hydrogen energetic compound DNDOBTT (2,7-dinitro-4N,9N-dioxide-bis[1,2,4]-triazolo)[1,5-b:1′,5′e][1,2,4,5] tetrazine) was produced by a new design concept of achieving a balance among the parent compound, nitro groups, and N-oxides. Its structure and properties was studied by the density functional theory. The breaking of N–N bond in the tetrazine ring is an initial decomposition step of DNDOBTT, and the energy barrier was predicted to be 175 kJ·mol−1. DNDOBTT has comparable detonation performance with some CHNO energetic compounds, including the most powerful ONC (octanitrocubane), whereas its sensitivity and thermal stability are obviously lower and better than those of ONC, respectively, indicating that DNDOBTT has both the high energy and reduced sensitivity and may be a valuable candidate for experiments. Therefore, a new novel energetic material DNDOBTT with good overall performance has been obtained successfully by the new design concept, and it may be applied to design and develop other novel improved zero-hydrogen energetic materials.

A facile strategy is reported to synthesize nitrogen-doped carbon quantum dots (N-CQDs) with fluorescence emission by a one-step hydrothermal treatment under different temperatures with dicyanodiamide and citric acid as precursor materials of nitrogen and carbon sources, respectively. The as-produced N-CQDs display green or blue fluorescence under the ultraviolet lamp was controlled by the reaction temperature. Consequently, the as-prepared sample reacted at 200[Formula: see text]C (N-CQDs-200), within the range of 3 nm, exhibits blue fluorescence excited at 365 nm irradiation with the maximum quantum yield (QY) of ca. 30.6%. Moreover, the N-CQDs possess rich functional groups such as nitrous groups and multiple oxygenated groups, which result in a favorable solubility in most hydrophilic solvents. From the characterization and discussion of TEM, HRTEM, FT-IR, XPS, Raman and UV-Vis, it is illustrated that the fluorescence performance was largely related to the nanomorphology, nitrogen concentration, multi-surface emission sites and various forms of transitions derived from the nitrogen doping. With the excellent fluorescence performance and the favorable solubility in solvents, the products are potentially suitable for monitoring organics.

We investigated the structural, electronic, vibrational and absorption properties of crystalline ammonium perchlorate (AP) at the pressure of 0–250 GPa by pure density functional theory and vdW-corrected DFT methods. It is found that a vdW correction is very necessary when studying the structure and properties of AP under different ranges of pressure, and the effects of vdW force are more obvious at a lower pressure than at a higher pressure. A structural transformation happens at 60 GPa and makes the positions of the anions and cations in the crystal rearrange. AP is chemically stable at all the investigated pressures and this unbelievable high stability is mainly due to its strong intermolecular hydrogen bonding. AP becomes more insensitive with the increment of pressure from 0 to 50 GPa, while the case is just the opposite when the pressure is increased from 50 to 250 GPa. The effect of the high pressure on the NH4 stretching mode is more pronounced than that on the ClO4 stretching mode, showing that the N–H bonds may be more easily compressed than the Cl–O bonds under compression; thus, N–H bonds are more possible to break under high pressure.

In this work, using hexaprismane as a base skeleton, we designed a novel cage energetic compound 1,3,5,7,9,11-hexaazahexaprismane-1,3,5,7,9,11-hexaoxdies (HAHHO) by employing a new design strategy: symmetrically replacing six carbon atoms by nitrogen atoms in hexaprismane followed by the introduction of six N-oxides. Its detonation performance and sensitivity were estimated by using the density functional theory method. It was found that HAHHO possesses much higher energetic performance than 1,3,5,7-tetranitro-1,3,5,7-tetrazocane and lower sensitivity than 2,4,6-trinitrotoluene, suggesting that its overall performance are outstanding and may be considered as the potential candidate of insensitive high explosives. The special double cage structure of HAHHO may be an important reason why it has low sensitivity. The results show that our strategy used for designing HAHHO is practical and may be applied to design and develop other cage explosives with high energy and low sensitivity.

In this work, six (A-F) nitramino (-NHNO2)-substituted ditetrazole 2-N-oxides with different bridging groups (-CH2-, -CH2-CH2-, -NH-, -N=N-, and -NH-NH-) were designed. The six compounds were based on the parent compound tetrazole 2-N-oxide, which possesses a high oxygen balance and high density. The structure, heat of formation, density, detonation properties (detonation velocity D and detonation pressure P), and the sensitivity of each compound was investigated systematically via density functional theory, by studying the electrostatic potential, and using molecular mechanics. The results showed that compounds A-F all have outstanding energetic properties (D: 9.1-10.0 km/s; P: 38.0-46.7 GPa) and acceptable sensitivities (h 50: 28-37 cm). The bridging group present was found to greatly affect the detonation performance of each ditetrazole 2-N-oxide, and the compound with the -NH-NH- bridging group yielded the best results. Indeed, this compound (F) was calculated to have comparable sensitivity to the famous and widely used high explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), but with values of D and P that were about 8.7% and 19.4% higher than those for HMX, respectively. The present study shows that tetrazole 2-N-oxide is a useful parent compound which could potentially be used in the design of new and improved high-energy compounds to replace existing energetic compounds such as HMX.

Novel optically active and racemic poly(N-propargylamides) bearing tyrosine pendants (LPT, DPT, and RPT) were synthesized and characterized. The polymers possessed moderate molecular weights and were thoroughly soluble in common organic solvents. The secondary structure of these three polymers in chloroform was studied and the results indicated that LPT and DPT could adopt helical structures with predominantly one-handed screw sense according to their intense Cotton effect and large specific rotation values, while RPT adopted random coiled polymer chain. The amide groups could form amide-amide hydrogen bonds to engender the twist of dihedral angle and the strong steric repulsion of phenol groups might have the opposite effect on the helix. The helical structure of the optically active polymers were conclusively constructed and stabilized by the optimization of intra- and intermolecular hydrogen bonding and steric repulsion of the side chains. Moreover, the infrared emissivity values of LPT and DPT at 30 °C were 0.682 and 0.671, which were much lower than RPT. LPT and DPT also showed superior heat resistance due to their unique helical conformation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44824.