The Acoustical Properties of Polymers at Low Temperatures

Perepechko, I. I.

doi:10.1016/b978-0-08-025301-5.50010-2

Cited by 12 publications

(23 citation statements)

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“…The experimental results for the specific heat at 2.5-4.9 K follow a T 3 law, as shown by Noer et aL [8], Reese and Tucker [3,9], and Scott and Giles [4]. However, these low-temperature calorimetric values of C/T 3 for T~ as well as those for T z are larger by more than 50~ compared to accoustic values [10] and give Oo x' = 102 K and 6)D x~--70 K.The reason for this discrepancy is unknown [11 ] for the time being. Some authors [12] point out that such a phenomenon may be provoked by the existence of low-frequency localized modes.…”

Section: Methodsmentioning

confidence: 70%

Specific heat of polytetrafluoroethylene and polychlorotrifluoroethylene within the temperature range 2.5–20 K

Terziiska

Mädge

Lovtchinov

1981

Journal of Thermal Analysis

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Low-temperature specific heat measurements on bulk technical polymer samples (polytetrafluoroethylene and polychlorotrifluoroethylene) were carried out between 2,5 and 20 K. In these experimental investigations a heat pulse method and an adiabatic vacuum calorimeter were used.The low-temperature specific heats of polytetrafluoroethylene (T4) and polychlorotrifluoroethylene (T3) have not been studied in sufficient detail [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. The extrapolation of the experimental values at 20 K down to 4 K by means of the Debye-model is inadmissible [5]. Thus, investigations of the thermal properties giving the necessary physical quantities and constants for cryogenic design of these highly crystalline polymers are quite important.In the present work, calorimetric measurements on the bulk polymer samples were made in the range 2.5-20 K. The length and diameter of the samples did not surpass 50 mm and 12 ram, respectively. By using a shield in a vacuum calorimeter [16], entirely adiabatic conditions of operation were ensured. The cooling of the calorimeter, as well as that of the sample and the shield, was effected with a mechanical heat switch [17]. The heat capacity was derived from a well-known relation between the increase of the sample temperature (A T ~ 10-2 T) and the amount of heat supplied to the sample by a 650 f2 heater, consisting of 0.050 mm diameter constantan wire. This heater gives heat impulses lasting 40 seconds. The temperatures of the samples and the shield were measured by 300~ Allen-Bradley resistors. The calibration of these resistors was performed using a germanium (NIG) substandard. The time for establishment of the heat equilibrium was a few seconds at 2.5 K, and about 15 minutes at 20 K. ExperimentalThe temperature-dependence of the specific heat is presented in Fig. 1 for polychlorotrifluoroethylene, and in Fig. 2

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Section: Methodsmentioning

confidence: 70%

Specific heat of polytetrafluoroethylene and polychlorotrifluoroethylene within the temperature range 2.5–20 K

Terziiska

Mädge

Lovtchinov

1981

Journal of Thermal Analysis

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“…The so-called Grüneisen constant, ␥, is also widely used to characterize anharmonicity in solids (Landau and Lifshitz, 1995), including organic polymers (Perepechko, 1977). Within the framework of Debye's theory of solids, this constant is defined as…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…‡ Calculated from a pressure-induced shortening of hydrogen bond length; pressures 0 -2 kbar. § Assuming the Poisson ratio to be within 0.33-0.41, as in glassy polymers (Perepechko, 1977). ¶ Extrapolated to ambient pressure by means of Moelwyn-Hughes' isotherm, Eq.…”

Section: Experimental Datamentioning

confidence: 99%

Protein Compressibility, Dynamics, and Pressure

Kharakoz

2000

Biophysical Journal

112

105

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The relationship between the elastic and dynamic properties of native globular proteins is considered on the basis of a wide set of reported experimental data. The formation of a small cavity, capable of accommodating water, in the protein interior is associated with the elastic deformation, whose contribution to the free energy considerably exceeds the heat motion energy. Mechanically, the protein molecule is a highly nonlinear system. This means that its compressibility sharply decreases upon compression. The mechanical nonlinearity results in the following consequences related to the intramolecular dynamics of proteins: 1) The sign of the electrostriction effect in the protein matrix is opposite that observed in liquids-this is an additional indication that protein behaves like a solid particle. 2) The diffusion of an ion from the solvent to the interior of a protein should depend on pressure nonmonotonically: at low pressure diffusion is suppressed, while at high pressure it is enhanced. Such behavior is expected to display itself in any dynamic process depending on ion diffusion. Qualitative and quantitative expectations ensuing from the mechanical properties are concordant with the available experimental data on hydrogen exchange in native proteins at ambient and high pressure.

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“…The reason the CTE of amorphous SEP containing ISB is lower than that of BPA-based polymers can be attributed to the unique chemical structure of ISB. According to quantum chemical calculations described in previously published articles, a fused aliphatic bicyclic ring exhibits considerably stronger geometrical restraint than the planar benzene structure of BPA, therefore, requiring a greater amount of energy for the same degree of alteration [48,49,50]. The ISB-based polymer with a higher Young’s modulus than the BPA-based polymer can be explained by the same principle.…”

Section: Resultsmentioning

confidence: 98%

Study on the Synthetic Characteristics of Biomass-Derived Isosorbide-Based Poly(arylene ether ketone)s for Sustainable Super Engineering Plastic

Park

et al. 2019

Molecules

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Demand for the development of novel polymers derived from biomass that can replace petroleum resources has been increasing. In this study, biomass-derived isosorbide was used as a monomer in the polymerization of poly(arylene ether ketone)s, and its synthetic characteristics were investigated. As a phase-transfer catalyst, crown ether has increased the weight-average molecular weight of polymers over 100 kg/mol by improving the reaction efficiency of isosorbide and minimizing the effect of moisture. By controlling the experimental parameters such as halogen monomer, polymerization solvent, time, and temperature, the optimal conditions were found to be fluorine-type monomer, dimethyl sulfoxide, 24 h, and 155 °C, respectively. Biomass contents from isosorbide-based polymers were determined by nuclear magnetic resonance and accelerator mass spectroscopy. The synthesized polymer resulted in a high molecular weight that enabled the preparation of transparent polymer films by the solution casting method despite its weak thermal degradation stability compared to aromatic polysulfone. The melt injection molding process was enabled by the addition of plasticizer. The tensile properties were comparable or superior to those of commercial petrochemical specimens of similar molecular weight. Interestingly, the prepared specimens exhibited a significantly lower coefficient of thermal expansion at high temperatures over 150 °C compared to polysulfone.

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The Acoustical Properties of Polymers at Low Temperatures

Cited by 12 publications

References 0 publications

Specific heat of polytetrafluoroethylene and polychlorotrifluoroethylene within the temperature range 2.5–20 K

Specific heat of polytetrafluoroethylene and polychlorotrifluoroethylene within the temperature range 2.5–20 K

Protein Compressibility, Dynamics, and Pressure

Study on the Synthetic Characteristics of Biomass-Derived Isosorbide-Based Poly(arylene ether ketone)s for Sustainable Super Engineering Plastic

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