ABSTRACT
The reduction of interfacial interaction and the deterioration of mechanical properties by the introduction of the paraffin wax is a long-standing problem. To address it, a novel litchi-like core-shell 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)@paraffin wax@polydopamine (PDA) structure was constructed with a new high melting point paraffin wax (HPW, 101.9 °C) as the inner shell and the bioinspired strong adhesive PDA as the exterior shell. The evolution of element states on the surface of energetic microcapsules conducted by X-ray photoelectron spectroscopy indicated the successful introduction of paraffin wax and PDA to form the core@double shell structure. Compared with the core@double shell particles based on the conventional low melting point paraffin wax (69.8 °C), the HMX@HPW@PDA particles demonstrated a 117% increase of impact energy EBAM from 6 J to 13 J by the Bundesanstalt für Materialprüfung (BAM) method. Attributed to the stronger interfacial interaction, the litchi-like core-shell HMX@paraffin wax@PDA-based energetic composites also exhibited much superior mechanical properties than that of the corresponding HMX@paraffin wax-based ones and could be equal to or even higher than that of the raw HMX-based ones. In addition, the ß-δ phase transition temperature of HMX in HMX@HPW@PDA crystals was improved by 11.3 °C than that of raw HMX. The simplicity and scalability of the described approach provided a creative opportunity for design and fabrication of energetic composites with high safety performance and mechanical properties.
ABSTRACT
The mechanical properties of composites are highly dependent on the interfacial interaction. In the present work, inspired by marine mussel, the adhesion between energetic crystals of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and polymer binders was improved. Three types of linear polymeric agents of glycidyl azide polymer (GAP), polyethylene glycol (PEG), and polytetramethylene ether glycol (PTMEG) were grafted onto TATB particles bridged through polydopamine (PDA) films. SEM images showed that 5% grafting contents could evidently form roughness shells on the surface. With a reinforcement at the interface produced by grafting shells, the mechanical properties of polymer-bonded explosives (PBXs) exhibited outstanding mechanical performance, especially for the PTMEG-grafting sample. Examined by the contact-angle test, the PTMEG-grafting sample possessed a value of polar component similar to that of fluoropolymer, leading to an excellent wettability of the two phases. Additionally, different contents of PTMEG were grafted to reveal that the mechanical properties could be improved even with content as little as 0.5 wt.% PTMEG. These results might highlight a correlation between interfacial interaction and macroscopic properties for mechanically energetic composites, while providing a versatile route of grafting on highly loaded composites.
ABSTRACT
A self-sustained municipal solid waste (MSW) pyrolysis-gasification process with self-produced syngas as heat source was proposed and an equilibrium model was established to predict the syngas reuse rate considering variable MSW components. Simulation results indicated that for constant moisture (ash) content, with the increase of ash (moisture) content, syngas reuse rate gradually increased, and reached the maximum 100% when ash (moisture) content was 73.9% (60.4%). Novel ternary diagrams with moisture, ash and combustible as axes were proposed to predict the adaptability of the self-sustained process and syngas reuse rate for waste. For wastes of given components, its position in the ternary diagram can be determined and the syngas reuse rate can be obtained, which will provide guidance for system design. Assuming that the MSW was composed of 100% combustible content, ternary diagram shows that there was a minimum limiting value of 43.8% for the syngas reuse rate in the process.