Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session P4: Soft Matter IV |
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Chair: Jennifer Jordan, Los Alamos National Laboratory Room: Regency Ballroom A |
Wednesday, July 12, 2017 11:15AM - 11:30AM |
P4.00001: Estimating the onset of reaction for porous reactive polymer systems David Fredenburg, Joshua Coe, Katie Maerzke, Dana Dattelbaum, John Lang Shock-induced volume changes are a feature common to many polymeric materials, where the volume change is associated with decomposition of the inert material into a reacted, `products' phase. The onset of this transition has been measured experimentally for many materials whose density is near theoretical, and, generally speaking, the onset is restricted to a relatively narrow range in pressures for near solid density materials. For initially porous polymeric materials, characterizing the onset of reaction with changes in initial porosity is much less well defined. The present work examines how the onset of reaction varies with initial porosity for several polymer systems, and presents a methodology for estimating this onset for an arbitrary initial density sample. [Preview Abstract] |
Wednesday, July 12, 2017 11:30AM - 11:45AM |
P4.00002: Deep-release of Epon 828 epoxy from the shock-driven reaction product phase John Lang, Anthony Fredenburg, Joshua Coe, Dana Dattelbaum A challenge in improving equations-of-state (EOS) for polymers and their product phase is the lack of off-Hugoniot data. Here, we describe a novel experimental approach for obtaining release pathways along isentropes from the shocked products. A series of gas-gun experiments was conducted to obtain release isentropes of the products for 70/30 wt\% Epon 828 epoxy resin/Jeffamine T-403 curing agent. Thin epoxy flyers backed by a low-density syntactic foam were impacted into LiF windows at up to 6.3 mm/$\mu$s, creating stresses in excess of those required for reaction ($\sim$25 GPa). Following a sustained shock input, a rarefaction fan from the back of the thin flyer reduced the pressure in the epoxy products along a release isentrope. Optical velocimetry (PDV) was used to measure the particle velocity at the epoxy/LiF interface. Numerical simulations using several different EOS describing the reactant-to-product transformation were conducted, and the results were compared with measured wave profiles. The best agreement with experiment was obtained using separate tabular EOS for the polymer “reactant” (e.g. epoxy) and product mixture, suggesting the transition to the products is irreversible. [Preview Abstract] |
Wednesday, July 12, 2017 11:45AM - 12:00PM |
P4.00003: Shock Wave Energy Dissipation using Polymerized Ionic Liquids Jaejun Lee, Yi Ren, Christopher Evans, Jeffrey Moore, Nancy Sottos Polymerized ionic liquids composed of alkyl-imidazolium cations and bis(trifluoromethane)sulfonamide anions exhibit intriguing shock wave energy absorption performance. In prior work, we observed a shock-induced disorder-to-order change in network forming ionic liquids. We hypothesize that this shock-induced ordering is strongly associated with the microstructure of the ionic liquids. Polymerized ionic liquids, which have similar microstructures but slower relaxation times compared to the ionic liquids, are prepared to demonstrate the ordering transition mechanism and to exploit relaxation processes for the energy dissipation. By employing size-tunable alkyl backbone spacers between cations, we explore the effect of the relative microstructural heterogeneity on the activation of shock-induced ordering. Relaxation time, which is adjustable by the alkyl spacer length, also plays an important role in the energy dissipation process. Absorption properties of a series of thin film (ca. 50 $\mu $m) polymerized ionic liquids are evaluated using a laser-induced shock wave testing protocol. Superior shock wave mitigating performance of polymerized ionic liquids was achieved compared to polyurea films. [Preview Abstract] |
Wednesday, July 12, 2017 12:00PM - 12:15PM |
P4.00004: Shock chemistry in SX358 foams Katie Maerzke, Joshua Coe, Anthony Fredenburg, John Lang, Dana Dattelbaum We have developed new equation of state models for SX358, a cross-linked PDMS polymer. Recent experiments on SX358 over a range of initial densities (0-65{\%} porous) have yielded new data that allow for a more thorough calibration of the equations of state. SX358 chemically decomposes under shock compression, as evidenced by a cusp in the shock locus. We therefore treat this material using two equations of state, specifically a SESAME model for the unreacted material and a free energy minimization assuming full chemical and thermodynamic equilibrium for the decomposition products. The shock locus of porous SX358 is found to be ``anomalous'' in that the decomposition reaction causes a volume expansion, rather than a volume collapse. Similar behavior has been observed in other polymer foams, notably polyurethane. [Preview Abstract] |
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