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A molecular dynamics simulation study of the pressure-volume-temperature behavior of polymers under high pressure
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10.1063/1.3077868
/content/aip/journal/jcp/130/14/10.1063/1.3077868
http://aip.metastore.ingenta.com/content/aip/journal/jcp/130/14/10.1063/1.3077868

Figures

Image of FIG. 1.
FIG. 1.

Repeat units for (a) poly(dimethyl siloxane), (b) poly(butadiene), (c) and Estane®, as well as the structures of the nitroplasticizers (d) used in np-Estane simulations, BDNPF and bis(2,2-dinitropropyl) acetal. In (a) and (b), the carbons represent UA carbons, while (c) and (d) are fully atomistic representations.

Image of FIG. 2.
FIG. 2.

(a) Comparison of experimental and simulation pressure vs compression data for Sylgard®/PDMS. Symbols represent data points from Dattelbaum et al. (Ref. 1) (diamonds), Marsh (Ref. 37) (hexagons), Sachdev et al. (Ref. 35) (triangles), Stevens et al. (Ref. 38) dilatometry (squares, empty) and Brillouin (squares, half-filled) experiments, and Dattelbaum et al. (pure) PDMS (Ref. 36) (stars) and simulation (circles). The lines represent the fitted Tait EOS for both fitted (solid) and universal (dashed) values of to the simulation data. The inset expands the low-pressure region of the data. (b) Comparison of the experimental and simulation data for Sylgard®/PDMS. All symbols and lines are as in (a). (c) Comparison of the experimental and simulation bulk modulus for Sylgard®/PDMS. All symbols and lines are as in (a).

Image of FIG. 3.
FIG. 3.

(a) Comparison of experimental and simulation pressure vs compression data of HTPB/PBD systems. Symbols represent data points from Barlow (Ref. 39) (hexagons), Gupta and Gupta (Ref. 40) (diamonds), and Millet et al. (Ref. 41) HTPB1 (triangles, up) and HTPB2 (triangles, down), and simulation (circles). The lines represent the fitted Tait EOS for both fitted (solid) and universal (dashed) values of to the simulation data. The inset expands the low-pressure region of the data. (b) Comparison of the experimental and simulation data for HTPB/PBD systems. All symbols and lines are as in (a).

Image of FIG. 4.
FIG. 4.

(a) Comparison of experimental and simulation pressure vs compression data for np-Estane. Symbols represent data points from Johnson et al. (Ref. 34) (squares), Gustavsen et al. (Ref. 33) dilatometry (triangles, up) and isentropic Z-Machine (triangles, down), and simulation (circles). The lines represent the fitted Tait EOS for both fitted (solid) and universal (dashed) values of . The inset expands the low-pressure region of the data. (b) Comparison of the experimental and simulation data for np-Estane. All symbols and lines are as in (a).

Image of FIG. 5.
FIG. 5.

(a) Comparison of experimental and simulation pressure vs. compression data for Estane®. Symbols represent data points from Johnson et al. (Ref. 34) (diamonds), Stevens et al. (Ref. 38) dilatometry (triangles down) and Brillouin scattering (triangles up), and Marsh (Ref. 37) (squares). The lines represent the as fit Tait EOS for both fitted (solid) and universal (dashed) values of . The inset expands the low-pressure region of the data. (b) Comparison of the experimental and simulation data for Estane®. All symbols and lines are as in (a).

Image of FIG. 6.
FIG. 6.

Comparison of the normalized pressure as a function of compression for the simulated PDMS (circles), PBD (squares), np-Estane (triangles), and model Estane® (diamonds) systems. The lines are normalized Tait equations of state [Eq. (6)] as fit for individual polymers (dash-dot-dot, short dashes, long dashes, dash-dot for PDMS, PBD, np-Estane, and model Estane® respectively) as well as utilizing the universal value of 0.089 36 (solid line).

Image of FIG. 7.
FIG. 7.

Comparison of the normalized curves ( vs ) for the as fit from the simulated PDMS (circles), PBD (squares), np-Estane (triangles), and model Estane® (diamonds) systems. The lines are normalized Tait fits [Eqs. (11) and (12)] for vs utilizing the parameter from PDMS (dash-dot-dot), PBD (short dashes), np-Estane (long dashes), model Estane® (dash-dot), and the universal parameter of 0.089 36 (solid).

Image of FIG. 8.
FIG. 8.

The Tait EOS predictions [Eq. (7)] for the normalized, pressure-dependent bulk modulus vs normalized pressure for fits utilizing the parameter derived from PDMS (dash-dot-dot), PBD (short dashes), np-Estane (long dashes), model Estane® (dash-dot), and the universal parameter of 0.089 36 (solid). The arrows representing the different polymers are located at a constant pressure of , and highlight the different rates of growth of the normalized modulus at constant pressure. The inset shows the growth in the normalized, pressure-dependent bulk modulus vs gauge pressure, where the lines have the same meaning as above and the symbols denote the simulated pressures for PDMS (circles), PBD (squares), np-Estane (triangles), and model Estane® (diamonds).

Image of FIG. 9.
FIG. 9.

Log of the pressure-dependent bulk modulus vs the logarithm of the fractional free volume for PDMS (circles), PBD (squares), np-Estane (triangles), and model Estane® (diamonds). The arrows denote the atmospheric value of the bulk modulus.

Image of FIG. 10.
FIG. 10.

The core volume normalized by the zero-pressure volume as a function of compression ratio for PDMS (circles), PBD (squares), np-Estane (triangles), and model Estane® (diamonds). The dashed line represents the asymptotic limit wherein compression has removed all the free volume from the system and the core volume ratio is equivalent to the overall compression ratio.

Image of FIG. 11.
FIG. 11.

The best-fit value of for the Tait EOS vs the atmospheric pressure free volume percentage for PDMS (circle), PBD (square), np-Estane (triangle), and model Estane® (diamond). The line is a linear fit with equation .

Tables

Generic image for table
Table I.

Summary of investigated polymers. Bolded values represent calculated quantities, while nonbolded represent reported data.

Generic image for table
Table II.

The Tait EOS parameters for the simulated systems. Shaded cells represent the “best-fit” values for the Tait EOS wherein both the and parameters were fitted. The nonshaded cells represent the fit produced utilizing the universal constant of 0.089 36.

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/content/aip/journal/jcp/130/14/10.1063/1.3077868
2009-04-09
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A molecular dynamics simulation study of the pressure-volume-temperature behavior of polymers under high pressure
http://aip.metastore.ingenta.com/content/aip/journal/jcp/130/14/10.1063/1.3077868
10.1063/1.3077868
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