Search

The design of a random copolymer comprising of 4-vinylbenzocyclobutene (4VBCB) and styrene as repeating units is presented herein. The effect of the 4VBCB to styrene ratio in the copolymer on the dielectric and thermodynamic properties of the materials was investigated using the molecular dynamics simulation technique. A script for the interactive crosslink relaxation method was developed using Perl as the language to control the crosslinking degree of the copolymers. This method was used to construct simulation units to generate highly crosslinked polymer networks from a given set of monomers. Three-dimensional simulation cells were constructed with the help of a computational algorithm and Materials Studio. The dielectric constants of the model were calculated using the existing polymer COMPASS force field by varying the monomer contents. The crosslinking degree was tuned to analyze the material properties. Several thermomechanical properties, such as curing-induced shrinkage, coefficient of thermal expansion, and glass transition temperature, were analyzed, and their dependence on the crosslinking degree was examined. The simulation results revealed that an increase in the crosslinking density resulted in an increase in the dielectric constant and glass transition temperature of the material. The extent of thermal expansion realized decreased under these conditions. The reliability of the simulation results was confirmed by comparing these results with experimentally-obtained results. The theoretically and experimentally obtained results demonstrated a close match within the acceptable error range. [ABSTRACT FROM AUTHOR]

Molecular dynamic (MD) simulations were employed to investigate the hexanitrohexaazaisowurtzitane (CL-20) crystal, seven designed energetic poly-(phthalazinone ether sulfone ketones) (PPESKs) and PPESKs/ε-CL-20 polymer–bonded explosives (PBXs). Cohesive energy density (CED) and solubility parameters (δ) were predicted for PBXs, the results indicated that stability of PBXs are related to their cohesive energy density (CED). Mechanical properties of seven polymer-bonded explosives (PPESKs/ε-CL-20) were found improved in comparison with that of ε-CL-20 by adding polymer binders. Young's modulus (E), Shear modulus (G), and Bulk modulus (K) declined compare with ε-CL-20. K/G ratio and Cauchy pressure C12-C44 of PBXs indicate that they have certain ductility. Radial distribution function (RDF) was utilized for analyzing the interactions between PPESKs and ε-CL-20, and results demonstrate that hydrogen bond and van der Waals interactions exist between polymers and ε-CL-20. The calculated oxygen balance of polymer-bonded explosives (PBXs) is lower than that of pure ε-CL-20 by nearly about − 24%. Detonation properties of the polymer-bonded explosives (PBXs) were predicted based on ε-CL-20 values. Detonation velocity (D) for these PBXs was predicted almost at about 8300 m s−1, and the detonation pressure (P) for these PBXs was all predicted nearly at 38 GPa. [ABSTRACT FROM AUTHOR]

The glass transition temperature ( T ) and density of poly-(phthalazinone ether sulfone ketone) (PPESK A) were estimated by molecular dynamic (MD) simulation. A novel poly-(phthalazinone ether sulfone ketone) (PPESK B) was constructed by introducing nitrol and amini energetic groups into PPESK A, and T and density were also simulated for PPESK B. The estimated T values of PPESK A were very close to experimental results, while for PPESK B three estimated values differed by < 5 K. The interactions between explosives and polymer binders of polymer bonded explosives (PBXs) were simulated by MD. Comparison of the cohesive energy densities (CED) and solubility parameter ( δ) values of PBXs, polymer binders, and mono-explosives indicate that, upon introducing polymer binders, the CED and δ values of PBXs decreased compared with those of corresponding mono-explosives. The binding energies ( E ) imply that 2,4,6-trinitrotoluene-based PBXs are more stable than 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-based PBXs. The mechanical properties, Young's modulus E, shear modulus G, bulk modulus K, Poisson's ratio γ and Cauchy pressure ( C -C ) of the PBXs were assessed. The rigidity of the PBXs was found to be lower than that of mono-explosives. All K/ G values were positive, indicating that PBXs are flexible. Based on these mechanical properties results, PBXs using PPESK B as a binder are superior to those using PPESK A as a binder. Due to the low C -C values of the PBXs, the ductility of the materials of the fracture surface is poorer, especially for TATB-based PBXs. [ABSTRACT FROM AUTHOR]