Thermal properties, measurement

The thermal properties measured by differential scanning calorimetry (Table IV) provide no structural information in the DMP-MPP system. Neither of the two homopolymers undergoes thermally-induced... 

Other attempts to avoid the experimental difficulties of measuring the thermal properties of gas hydrates have been to choose the easier route of thermal property measurements of cyclic ethers-ethylene oxide (EO) for structure I, or tetrahydro-furan (THF) for structure II. Since both compounds are totally miscible with water, liquid solutions can be made at the theoretical hydrate compositions (EO 7.67H20 or THF 17H20). 

Table 6.5 lists the different thermal property measurements that have been performed on hydrates of cyclic ethers, other nonnatural gas components, and natural gas components. 

In attempting to model the heat transfer-controlled behavior, we were surprised to find, in the literature, a significant variability in the key thermal properties that such a model required. Quite different predictions could result from using different assumptions regarding the thermal properties. To address this obviously significant impediment to reliable model development, an experimental program focusing on thermal property measurements was initiated. The results are summarized below. 

METAL FABRIC AND SILICON MATERIALS. THERMAL PROPERTY MEASUREMENTS REPORT. 

There are few reports of thermal property measurements (e.g., thermal conductivity, specific heat, etc.) [52, 53]. The linear term in specific heat at low temperatures is evidence of the continuous density of states with a well-defined Fermi energy for any metallic system. The low temperature specific heat, C, for a metallic PPy-PFg sample and for an insulating PPy-p-toluenesulfonate (TSO) sample is shown in Figure 2.13 [54]. The data for both samples fit to the equation C/T = y+ jS P, where yand P are the electronic and lattice contributions, respectively. From the values of P and y, the calculated density of states for metallic and insulating samples are 3.6 0.12 and 1.2 0.04 states per eV per unit, and the corresponding Debye temperatures are 210 7 and 191 6.3 K, respectively. These values are comparable to those obtained from the spin susceptibility data. 

The thermal property measurement techniques can be categorized as steady-state methods and transient methods. They can also be categorized as invasive and noninvasive techniques. In the following sections, we will focus on several widely used techniques for measuring tissue thermal conductivity or diffusivity. Their advantages and limitations will also be described. 

The thermal property measurements (e.g., thermal conductivity, specific heat, etc.) are rather few in doped conducting polymers [1148,1149]. The linear term in specific heat at low temperatures is characteristic evidence of the continuous density of states with a well-defined Fermi energy for any metallic system. The low-temperature specific heat for a metallic PPy-PF6 sample and for... 

Density, mechanical, and thermal properties are significantly affected by the degree of crystallinity. These properties can be used to experimentally estimate the percent crystallinity, although no measure is completely adequate (48). The crystalline density of PET can be calculated theoretically from the crystalline stmcture to be 1.455 g/cm. The density of amorphous PET is estimated to be 1.33 g/cm as determined experimentally using rapidly quenched polymer. Assuming the fiber is composed of only perfect crystals or amorphous material, the percent crystallinity can be estimated and correlated to other properties. 

Cell si has been characterized by measurements of the cell diameter in one or more of the three mutually perpendicular directions (143) and as a measurement of average cell volume (144,145). Mechanical, optical, and thermal properties of a foam are all dependent upon the cell size. 

A knowledge of the viscous and thermal properties of non-Newtonian fluids is essential before the results of the analyses can be used for practical design purposes. Because of the nonlinear nature, the prediction of these properties from kinetic theories is as of this writing in its infancy. Eor the purpose of design and performance calculations, physical properties of non-Newtonian fluids must be measured. 

Thermal Properties. Thermal properties include heat-deflection temperature (HDT), specific heat, continuous use temperature, thermal conductivity, coefficient of thermal expansion, and flammability ratings. Heat-deflection temperature is a measure of the minimum temperature that results in a specified deformation of a plastic beam under loads of 1.82 or 0.46 N/mm (264 or 67 psi, respectively). Eor an unreinforced plastic, this is typically ca 20°C below the glass-transition temperature, T, at which the molecular mobility is altered. Sometimes confused with HDT is the UL Thermal Index, which Underwriters Laboratories estabflshed as a safe continuous operation temperature for apparatus made of plastics (37). Typically, UL temperature indexes are significantly lower than HDTs. Specific heat and thermal conductivity relate to insulating properties. The coefficient of thermal expansion is an important component of mold shrinkage and must be considered when designing composite stmctures. 

The disadvantage is that volumetric efficiency is usually much less than conventional trays or packed contactors. Applications are usually limited to cases when only a few transfer units or a single eqiiihbriiim stage is required. Since many of these applications tend to be in heat-transfer sei vice, the following discussion will be in terms of thermal properties and thermal measures of performance. 

Thermal properties of overlayer atoms. Measurement of the intensity of any diffracted beam with temperature and its angular profile can be interpreted in terms of a surface-atom Debye-Waller factor and phonon scattering. Mean-square vibrational amplitudes of surfece atoms can be extracted. The measurement must be made away from the parameter space at which phase transitions occur. 

The glass transition temperatures of the nylons appear to be below room temperature so that the materials have a measure of flexibility in spite of their high crystallinity under general conditions of service. The polymers have fairly sharply defined melting points and above this temperature the homopolymers have low melt viscosities. Some thermal properties of the nylons are given in Table 18.4. 

All VGCF was graphitized prior to composite consolidation. Composites were molded in steel molds lined with fiberglass reinforced, non-porous Teflon release sheets. The finished composite panels were trimmed of resin flash and weighed to determine the fiber fraction. Thermal conductivity and thermal expansion measurements of the various polymer matrix composites are given in Table 6. Table 7 gives results from mechanical property measurements. 

This phenomenon can be demonstrated by both measuring the changes of the thermal properties of the ECA homopolymer and in adhesion tests. The addition of only 1 wt.% of 9 to a sample of the ECA homopolymer significantly increases the onset of decomposition in the thermogravimetric analysis (TGA) of the polymer, as seen in Fig. 9 [29]. 

We observe that all constants in (4) or (5) can be determined by measurements of the thermal properties of the system, with the exception of a or A, which are indeterminate from the point of view of classical thermodynamics. 

E7.9 The following thermal properties have been measured for sodium hydroxide solutions at 298.15 K. 

In order to simplify the procedure of evaluating the extent of mesophase and its mechanical and thermal properties, a simple but effective three-layer model may be used, which is based on measurements of the thermal expansions of the phases and the composite, below and above the transition zone of the composite, lying around its glass transition temperature Tgc. 

Closely related mixed amido/imido/guanidinato tantalum complexes of the type Ta(NR R )[(R R2N)C(NR )2]( = NR ) (R R = Me, Et R = Cy, Pr R = Pr", BuO were synthesized by the insertion of carbodiimides into to tantalum-amide bonds in imidotantalum triamide precursors, and the effects of ligand substitution on thermal properties were studied by TGA/DTA measurements. In addition, selected compounds were pyrolyzed at 600 °C and the decomposition products were studied by GC-MS and NMR spectroscopy. ... 

Recent advances in the application of ultrafine talc for enhanced mechanical and thermal properties have been studied [12]. A particularly important use is of finely divided filler in TPO as a flame-retardant additive. In a representative formulation, 37 parts of E-plastomer, Ml 2.0, density 0.92, 60 parts of amorphous EPR, and 4 parts of fine carbon black were dry blended, kneaded at 180°C, pelletized, and press molded into test pieces, which showed oxygen index 32 versus 31 in the absence of a filler. The oxygen index is a measure of flame retardancy. 

Thermal Properties. The glass transition temperature (Tg) and the decomposition temperature (Td) were measured with a DuPont 910 Differential Scanning Calorimeter (DSC) calibrated with indium. The standard heating rate for all polymers was 10 °C/min. Thermogravimetric analysis (TGA) was performed on a DuPont 951 Thermogravimetric Analyzer at a heating rate of 20 °C/min. 

Austin, W.A., 1998. Development of an In-Situ System for Measuring Ground Thermal Properties, MSc. Thesis, Oklahoma State University, USA, 164 pp. 

Austin, W.A., C. Yazuzturk, and J.D. Spitler, 2000. Development of an in-situ system for measuring ground thermal properties, ASHRAE Trans., 106 (1) 365-379. 

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