Ammonium Polyphosphate Intercalated Layered Double Hydroxide and Zinc Borate as Highly Efficient Flame Retardant Nanofillers for Polypropylene

We found in our previous study that layered double hydroxides (LDHs) which undergo aqueous miscible organic solvent treatment (AMOST) can tune the hydrophobicity surface of LDHs to be hydrophobic, and then the solvent mixing method can be used to prepare polymer/LDH nanocomposites. However, flame retardant property is not very high if LDHs are only used. In this present work, ammonium polyphosphate (APP) intercalated LDHs and zinc borate (ZB) was incorporated into a polypropylene (PP) matrix using the solvent mixing method. The structures, morphologies, and performance of the composites were characterized carefully. The peak heat release rate (PHRR) reduction of PP containing 10 and 20 wt % APP-LDH reached 27% and 55%, respectively, which increased up to 63% compared with PP/CO3-LDH. After incorporating 2 wt % ZB in the PP/APP-LDH system, the flame retardant property was further improved. Polypropylene composites with 20 wt % APP-LDH and 2 wt % ZB showed a 58% PHRR reduction. In addition, thermogravimetric analyzer (TGA) results indicated that the addition of APP-LDH and ZB improved the temperature at 50% weight loss (T50%) and the char formation of the materials significantly

A knowledge-based web platform for collaborative physical system modeling and simulation

A web platform, called Proteus (http://www.visualphysics.net/pweb), has been developed by a team in Nanyang Technological University. This platform is designed for education and academic research, and is free to use. It provides a place where students, educators, and academic researchers can easily create and share their computer models of physical systems described using Modelica, a non-proprietary, object-oriented, equation-based language for physical system modeling. It comes with a web-based, graphical modeling, and simulation tool called ProteusGWT (http://www.visualphysics.net/ProteusGWT). ProteusGWT is web-based and uses an intuitive, graphical component-oriented approach to the modeling of physical systems spanning multiple domains including systems containing mechanical, hydraulic, thermal, control, electrical, electronic, electric power, or process-oriented subcomponents. It synthesizes state-of-the-art web technologies (e.g., HTML5, GWT, and cloud computing), computational methods for physical systems modeling, and simulation to create a computing environment that is widely deployable and scalable. Google Web Toolkit (GWT) is a development toolkit from Google for building and optimizing complex web-based applications. It allows developers to create and maintain complex JavaScript applications in Java language. Proteus allows anyone with a computer or browser-enabled device to be able to use it. Hence, anyone can contribute their computer models of physical systems to this platform. As this platform grows, it could turn out to be an online interactive repository for all kinds of physical system models, for example, a student may examine complete computer models of a motorcycle, a refrigerator, a burglar alarm, or robot arm and learn about how they work. He or she could run simulations, modify the models, or create new designs and share with others. There is nothing quite like this currently on the Internet

Mechanism of Organoscandium-Catalyzed Ethylene Copolymerization with Amino-Olefins: A Quantum Chemical Analysis

The direct, efficient copolymerization of ethylene with polar monomers represents a "holy grail" for the synthesis of polar polyethylenes; however, developing effective catalysts for such copolymerizations remains a largely unsolved challenge. Very recently, organoscandium catalysts were shown to be very active for ethylene + polar monomer [H2C=CH(CH2)(n)CH(2)FG, FG = polar functional group] copolymerization. Interestingly, comonomer enchainment selectivity decreases with increasing linker length (n), while overall polymerization activity is largely unaffected, and the intriguing mechanistic origins are not yet understood. In this study, density functional theory (DFT) methods are employed to investigate the mechanism of organoscandium-catalyzed ethylene + amino olefin (AO) copolymerization, using (C5Me4SiMe3)Sc(CH2CH2CH3)B+(C6F5)(4)(-) (Sc-1) as the model active species and N-(1-butenyl)"Pr-2 and N-(1-octenyl)"Pr-2 as model comonomers. Among conceivable scenarios in monomer coordination, activation, and insertion, it is found that copolymerization activity is largely governed by intermolecular amino olefin N-coordination. Amino olefin n-dependent enchainment patterns arise from chain-length regulation of the energy barrier for an amino olefin chelating "self-assisted" enchainment pathway. Short-chain N-(1-butenyl)"Pr-2 enchains via a self-assisted insertion pathway (6.0 kcal/mol energy barrier), while long-chain N-(1-octenyl)"Pr-2 enchains via unassisted 1,2-insertion with exogenous amine coordination (7.2 kcal/mol energy barrier). These findings explain the experimental results, showcase the characteristic reactivity of Sc catalysts in polar monomer copolymerization, and highlight the potential and challenges in developing catalysts for polar monomer copolymerization

Detection Method and Experimental Research of Leafy Vegetable Seedlings Transplanting Based on a Machine Vision

In view of the need to remove empty cells and unqualified seedlings for automatic transplanting of leafy vegetable seedlings, this paper proposes a method to detect the growth parameters of leafy vegetable seedlings by using machine vision technology. This method uses the image processor PV200 to perform image grayscale, threshold segmentation, corrosion, expansion, area division, etc. to obtain the pixel value of the leaf area of the seedling and compare it with the set standard value, which provides guiding information for eliminating empty cells and unqualified seedlings. Lettuce seedlings at 17 days, 20 days, and 22 days of seedling age were used as the test objects, and the growth status and test results of the seedlings were analyzed to determine the optimum seedling age for transplanting. The test results show that there is basically no leaf cross-border between the lettuce seedlings at the age of 17 days, the average pixel area of the leaves is 3771.74, and the detection accuracy rate is 100%; the seedlings at the age of 22 days grow 5–6 leaves, the detection accuracy of unqualified seedlings and qualified seedlings was 62.50% and 88.16%, respectively, and the comprehensive detection accuracy was 85.71%. The comprehensive detection accuracy rate showed a downward trend with the increase of seedling age, mainly due to the partial occlusion between leaves. The transplanting of leafy vegetable seedlings is a sparse transplanting operation, and the seedling spacing increases after transplanting. Therefore, the detection of seedlings in the process of transplanting can greatly improve the recognition accuracy and solve the problem that the leaves of the seedlings in the seedling tray are obscured by each other and affect the detection accuracy. The research results can provide a theoretical basis and design reference for the development of the visual inspection system and the transplanting actuator of the leafy vegetable seedlings transplanting robot

<p>Simultaneously achieving selective catalytic reduction of NOx with NH3 and catalytic oxidation of CO with O-2 over one finely optimized bifunctional catalyst Mn2Cu1Al1Ox at low temperatures</p>

For coke oven flue gases, the simultaneous removal of NOx and CO pollutants is highly demanded but still re-mains a big challenge. So far there isn't a single efficient catalyst that can simultaneously achieve selective catalytic reduction of NOx by NH3 and the catalytic oxidation of CO to CO2 in the presence of excessive O-2 at low temperatures (180-220 ?). Here, we report a bifunctional catalyst Mn2Cu1Al1Ox that possesses dual active sites and is highly active for both NH3-SCR and CO oxidation reactions under the above mentioned conditions. By tuning the redox properties and surface oxygen vacancies, the optimized Mn2Cu1Al1Ox catalyst achieved high conversions of both NOx and CO in the NH3-NO-CO-O-2 system, with a NOx conversion of 86.8% and a CO conversion of 100% at 200 ?. The active reaction sites and the interaction principal between NH3-SCR and CO oxidation reactions were thoroughly investigated by well-designed experiments, in-situ DRIFTS and DFT calculations. It was revealed that NH3 and CO competed for the same active sites, which significantly influenced the catalytic performance of Mn3Al1Ox and Cu3Al1Ox for CO oxidation reactions. For the bifunctional Mn2Cu1Al1Ox catalyst, CO is more easily adsorbed on the Cu sites, while NH3 is more inclined to adsorb on the Mn sites, which enables both NH3-SCR and CO oxidation reactions to proceed simultaneously on one catalyst. The improvement of CO oxidation performance on Mn2Cu1Al1Ox catalyst is mainly attributed to the reduced Jahn-Teller effect of Cu atoms by doping into Mn3O4, which leads to the lift of d-band center and finally enhances the CO adsorption

Development of Quinary Layered Double Hydroxide-Derived High-Entropy Oxides for Toluene Catalytic Removal

In this work, a novel method for the preparation of high-entropy oxides (HEO) was successfully developed using multivariate composition layered double hydroxides (LDHs) as precursor. Thermal treatment over 600 °C led to the complete transformation of LDHs to single spinel phase HEOs. The performance of the obtained HEO catalysts in the removal of volatile organic compounds (VOCs) was studied with the catalytic oxidation of toluene as the probe reaction. The optimized HEO-600 catalyst showed impressive activity and stability over toluene catalytic oxidation, which resulted from the vast quantity of surface oxygen vacancies and the relative variable metal valence. The T50 and T90 values of HEO-600 were 246 and 254 °C, and the T90 value only presented a slight increase to 265 °C after a 10-cycle test. This work developed a simple way to obtain HEO materials and provide technical support for the application of HEO catalysts for VOCs removal

Significant Polar Comonomer Enchainment in Zirconium‐Catalyzed, Masking Reagent‐Free, Ethylene Copolymerizations

AbstractIn principal, the direct copolymerization of ethylene with polar comonomers should be the most efficient means to introduce functional groups into conventional polyolefins but remains a formidable challenge. Despite the tremendous advances in group 4‐centered catalysis for olefin polymerization, successful examples of ethylene + polar monomer copolymerization are rare, especially without Lewis acidic masking reagents. Here we report that certain group 4 catalysts are very effective for ethylene + CH2=CH(CH2)nNR2 copolymerizations with activities up to 3400 Kg copolymer mol−1‐Zr h‐1 atm‐1, and with comonomer enchainment up to 5.5 mol % in the absence of masking reagents. Group 4 catalyst‐amino‐olefin structure–activity‐selectivity relationships reflect the preference of olefin activation over free amine coordination, which is supported by mechanistic experiments and DFT analysis. These results illuminate poorly understood facets of d0 metal‐catalyzed polar olefin monomer copolymerization processes

Layered double hydroxide-oxidized carbon nanotube hybrids as highly efficient flame retardant nanofillers for polypropylene.

Aqueous miscible organic layered double hydroxides (AMO-LDHs) can act as organophilic inorganic flame retardant nanofillers for unmodified non-polar polymers. In this contribution, AMO [Mg3Al(OH)8](CO3)0.5·yH2O LDH-oxidized carbon nanotube (AMO-LDH-OCNT) hybrids are shown to perform better than the equivalent pure AMO-LDH. A synergistic effect between the AMO-LDH and OCNT was observed; this endows the hybrid material with enhanced flame retardancy, thermal stability, and mechanical properties. The thermal stability of polypropylene (PP) was significantly enhanced by adding AMO-LDH-OCNT hybrids. For PP mixed with AMO-LDH-OCNT hybrids to produce a composite with 10 wt% LDH and 2 wt% OCNT, the 50% weight loss temperature was increased by 43 °C. Further, a system with 10 wt% of AMO-LDH and 1 wt% OCNT showed a peak heat release rate (PHRR) reduction of 40%, greater than the PHRR reduction with PP/20 wt% AMO-LDH (31%). The degree of dispersion (mixability) between AMO-LDH and OCNT has a significant effect on the flame retardant performance of the hybrids. In addition, the incorporation of AMO-LDH-OCNT hybrids led to better mechanical properties, such as higher tensile strength (27.5 MPa) and elongation at break (17.9%), than those composites containing only AMO-LDH (25.6 MPa and 7.5%, respectively)