Synthesis of Zinc Phosphonated Poly(ethylene imine) and Its Fire-Retardant Effect in Low-Density Polyethylene

A novel oligomeric intumescent fire-retardant chelate, zinc phosphonated poly(ethylene imine) (Zn-PEIP), with a variable Zn2+ loading, was synthesized. The chemical structure of Zn-PEIP was confirmed by FTIR, 13C NMR, and 31P NMR spectroscopies. The thermal behavior and fire retardancy of low-density polyethylene (LDPE) containing 25 wt % Zn-PEIPs with different amounts of Zn2+ were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) measurements, and cone calorimetry. The TGA results showed that higher concentrations of Zn2+ improved the thermal stability and increased the residue yield of LDPE. However, the data from the LOI and cone calorimetry tests showed that there is an optimum concentration of Zn2+ for the best fire-retardancy performance of LDPE. This behavior is ascribed to the high cross-link density resulting from zinc bridges, preventing normal swelling of the intumescent system. The surface morphology of the char was characterized by digital photography and scanning electron microscopy (SEM). This confirmed the optimum intumescence and coherent and strong barrier layer formation at an intermediate Zn2+ loading

MP2 and DFT studies of beta-D-neocarrabiose and beta-D-neocarrabiose monohydrate

International audienceMP2 and density functional theory calculations have been carried out on beta-D-neocarrabiose and its mono hydrate in order to determine the conformational preferences of these molecules in the gas phase and in solvent. Relaxed iso-energetic maps were first obtained using B3LYP/6-31G(d). Then, the lower energy conformers were further fully optimized using B3LYP, B3PW91 and MP2 methods. Overall, it was demonstrated that a lower energy conformer corresponding to the couple of dihedral angles (Phi,Psi)= (69 degrees,-117 degrees) is detected either in the gas phase or in solvent provided that full optimizations are performed on the conformers corresponding to the minima detected from the iso-energetic maps. (C) 2016 Elsevier B.V. All rights reserved

3D waypoint generation in a dynamic environment for an airborne launch mission

International audienceThe airborne launch vehicle, studied in this article, has to find an appropriate route to reach the mission goal, considering environment requirements and system constraints, for mission safety and efficiency. A method for three-dimensional waypoint generation based on an improved version of the A* algorithm with avoidance of detected obstacles is presented in this article. As the mission proceeds, the information about the environment is regularly updated. This information is considered in the mission plan, yielding a revised sequence of waypoints, to reach one or multiple goal points, depending on their order of priority. The output of the algorithm is twofold: a dynamic waypoint generation and a shortest route refined regularly. Diverse obstacles such as turbulence zones, no-fly zones, storms, etc., are considered in the flight plan as soon as they are detected. Their locations and shapes are introduced into the path search space. The improved A* capabilities are tested via simulation in different scenarios