Temperature dependence of compression of linear high polymers at high pressures

Weir, C.E.

doi:10.6028/jres.053.031

Cited by 88 publications

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“…Extrapolated to 5.5 kbar, it has the value 0.00088 cal cm -• s-' øC-' and by 30 kbar increases to 0.00187 cal cm -• s-' øC-'. This increase in conductivity for Teflon III is 5.5% kbar -z, somewhat lower than the (7and decreases by 15% across the Teflon II-III phase change, in good agreement with the decrease across the phase change predicted byWeir [1954] from thermal expansion and compressibility data.Quartz. The thermal diffusivity of single-crystal quartz was measured perpendicular to the c axis(Figure 9).…”

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confidence: 79%

Experimental determination of the pressure dependence of the thermal diffusivity of teflon, sodium chloride, quartz, and silica

Kieffer¹,

Getting²,

Kennedy³

1976

J. Geophys. Res.

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The thermal diffusivity of Teflon, sodium chloride, quartz, and silica glass was measured at 40° C to pressures of 35, 18, 30, and 36 kbar, respectively. A transient line source method was modified for use in a piston‐cylinder high‐pressure cell. Pressure gradients were determined by experiments with bismuth foils. The pressure dependence of the thermal diffusivity at 40°C for the substances studied may be represented as follows (κ in square centimeters per second, P in kilobars): for the low‐pressure phases of Teflon, Teflon I‐II, P < 5.5 kbar, κ = 0.0012 + 3.6 × 10−5P; for the high‐pressure phase, Teflon III, 5.5 kbar < P < 35 kbar, κ = 0.0012 + 8.0 × 10−5 P; for polycrystalline halite, P < 18 kbar, κ = 0.0031 + 9.5 × 10−4 P; for quartz, perpendicular to the c axis, P < 30 kbar, κ = 0.031 + 5.3 × 10−4 P; for silica glass, P < 36 kbar, κ = 0.0068 — 6.7 × 10−6 P. The diffusivity of silica glass decreases with pressure, in contrast to the diffusivity of its crystalline counterpart, quartz, which increases with pressure. In addition to the diffusivity the thermal conductivity of Teflon was determined by measuring the power applied to the heater wire. The thermal conductivity of a Teflon I‐II mixture is approximately constant at 0.0075–0.0078 cal/cm s °K to 5.5 kbar. Above 5.5 kbar the conductivity of Teflon III is given by K = 0.0062 + 4.0 × 10−5P. The specific heat of Teflon decreases with pressure and decreases discontinuously by 15% across the Teflon II‐III phase change, in good agreement with the decrease predicted from thermal expansion and compressibility data.

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confidence: 79%

Experimental determination of the pressure dependence of the thermal diffusivity of teflon, sodium chloride, quartz, and silica

Kieffer¹,

Getting²,

Kennedy³

1976

J. Geophys. Res.

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“…Phase II PTFE consists of a helical conformation with a 13 atom repeat unit and a well-ordered hexagonal packing of the helical chains, while in phase III the helical conformation gives way to a planar zig-zag and the chain packing takes on an orthorhombic or monoclinic lattice structure. Recent work using a high-pressure diamond-anvil cell and near-infrared Raman (NIR) spectroscopy suggests the transition occurs at 0.65 GPa and exhibits around ±0.05 GPa of hysteresis [48][49][50][51] The phase transition results in a 13 % local volume change within the crystalline domains and a considerable reduction in compressibility. PTFE also exhibits two atmospheric pressure, crystalline transitions at 19 and 30°C [52].…”

Section: Shock Compressionmentioning

confidence: 99%

On the Shock Response of Polymers to Extreme Loading

Bourne

2016

J. dynamic behavior mater.

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This paper reviews polymer response to shock and discusses how plastics behave differently depending on the strain rate applied. The author uses polyethylene, polytetrafluroethylene, polycarbonate and epoxy as example materials. It is suggested that there are two distinct regimes of polymer response corresponding to low and high shock pressures (weak and strong shock regimes) that must be considered separately. Above a high pressure threshold it is proposed that polymers homogenize to carbon-containing structures which behave similarly. Further, the yield stress of a polymer volume element asymptotes to the theoretical strength of the material as volume shrinks to zero. It is suggested that these two behaviours reflect the same physics and this feature is common to the condition identified earlier for crystalline materials.

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“…All the samples were homogenized using a SPEX/MIXER 81057 at 1400 rpm for 15 min. The homogenized mixture was compacted in a mold at a pressure of 40 MPa and 4008C, under nitrogen atmosphere, 10 min [15]. To verify that the PMMA matrix did not present changes in its molecular weight, a dilute solution viscosimetry analysis was carried out.…”

Section: Methodsmentioning

confidence: 99%

Structural, electrical and percolation threshold of Al/polymethylmethacrylate nanocomposites

2009

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Aluminum-embedded polymethylmethacrylate (PMMA) composites were produced by using different aluminum concentrations in the polymer matrix. The aluminum particles were spherical with a particle size of 80 nm. The hot compression molding method in inert atmosphere for all the composites was used in their preparation. The PMMA matrix was analyzed using solution viscosimetry analysis and it did not evidence degradation of the PMMA matrix. The microstructure of the composites was examined with scanning electron microscopy (SEM). The electrical conductivity was measured as a function of the aluminum content and the composite fabricated with 10 vol.% aluminum presented a conductivity three order of magnitude higher than that of pure PMMA. The enhancement in conductivity can be explained by means of segregated percolation path theory and the experimental results are in agreement with the theoretical law. POLYM. COMPOS.,

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Temperature dependence of compression of linear high polymers at high pressures

Cited by 88 publications

References 0 publications

Experimental determination of the pressure dependence of the thermal diffusivity of teflon, sodium chloride, quartz, and silica

Experimental determination of the pressure dependence of the thermal diffusivity of teflon, sodium chloride, quartz, and silica

On the Shock Response of Polymers to Extreme Loading

Structural, electrical and percolation threshold of Al/polymethylmethacrylate nanocomposites

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