Thermal Expansion of Amorphous Polymers at Atmospheric Pressure. II. Theoretical Considerations

1973 ◽  
Vol 6 (6) ◽  
pp. 908-914 ◽  
Author(s):  
Robert Simha ◽  
Phillip S. Wilson
Keyword(s):  
Thermal Expansion ◽  
Atmospheric Pressure ◽  
Amorphous Polymers ◽  
Theoretical Considerations

Deformation of Polymers During Hydrostatic Extrusion

1978 ◽  
Vol 100 (4) ◽  
pp. 400-405 ◽  
Author(s):  
N. Inoue ◽  
T. Nakayama ◽  
M. Shimono
Keyword(s):  
Atmospheric Pressure ◽  
High Density Polyethylene ◽  
Theoretical Basis ◽  
Superposition Principle ◽  
Amorphous Polymers ◽  
Extrusion Process ◽  
Extrusion Ratio ◽  
Tension Tests ◽  
Effects Of Temperature ◽  
Temperature Time

Crystalline as well as amorphous polymers and a thermosetting resin were hydrostatically extruded with pressures up to 4 kilobars. A linear relation was obtained between the extrusion pressure and extrusion ratio. Temperature of the billets during the extrusion process was determined, along with the flow pattern of the deformation. Tension tests at the temperature, to which the billet was exposed during the extrusion, was carried out at atmospheric pressure on the high-density polyethylene specimen to supply a theoretical basis to the experimental formula. Effects of temperature and strain rate on the extrusion process are discussed in the light of the temperature-time superposition principle.

The structural behaviour of tetrahedral framework compounds — a review Part II. Framework structures

1984 ◽  
Vol 48 (346) ◽  
pp. 65-79 ◽  
Author(s):  
D. Taylor
Keyword(s):  
Thermal Expansion ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Structural Changes ◽  
Structural Data ◽  
Structural Behaviour ◽  
Tetrahedral Framework ◽  
Cell Parameters ◽  
Silicon And Germanium ◽  
Framework Compounds

AbstractTetrahedral framework compounds, as defined in this paper, generally exist as tilted and distorted versions of ideal fully expanded structures at room temperature and atmospheric pressure. How pressure, temperature, and composition (P, T, and X) affect the tilting and distortion is critically reviewed. It is shown that although the effects of P, T, and X on the cell parameters are broadly analogous, the underlying structural changes are generally different. An important, and frequently neglected thermal effect is the apparent shortening of the framework bonds by the anisotropic thermal motion of the framework oxygens. Tilting models of framework compounds are critically examined and their failure to match the observed structural behaviour is attributed to changes in tetrahedral distortion. For quartz it appears that during compression the change in tetrahedral distortion is virtually all angular (O-Si-O angles), whereas during thermal expansion the change in distortion is in the Si-O distances. Such behaviour may typify the behaviour of many other framework compounds but the structural data needed to establish this are lacking. The review is illustrated by reference to the quartz and cristobalite analogues; to the sodalite, leucite, nepheline, scapolite, and feldspar families; and to the nitrides and oxynitrides of silicon and germanium. It is concluded that our understanding of the structural behaviour of framework compounds is still superficial and that much theoretical and experimental work remains to be done.

scholarly journals Theoretical And Experimental Investigation Of Thermodiffusion (Soret Effect) In A Porous Medium

2021 ◽  
Author(s):  
Tawfiq J. Jaber
Keyword(s):  
Porous Medium ◽  
High Pressure ◽  
Thermal Expansion ◽  
Equation Of State ◽  
Atmospheric Pressure ◽  
Soret Effect ◽  
Ternary Mixtures ◽  
Hydrocarbon Mixtures ◽  
Expansion Coefficients ◽  
Robinson Equation

Thermodiffusion (the Soret effect) is important for the study of compositional variation in hydrocarbon reservoirs. The development of research history, theoretical modeling and applications to multicomponent hydrocarbon mixtures is included in this work. The Firoozabadi model appears to be an appropriate model for thermodiffusion estimation for hydrocarbon mixtures, and it is derived based on the equation of entropy generation rate and four postulates in non-equilibrium thermodynamics. Two equations of state, the Peng-Robinson Equation of State (PR-EoS) and the volume translated Peng Robinson Equation of State (vt-PR-EoS), have been used to estimate the thermodynamic properties of mixtures. In this work, different cases are presented: first, a new thermodiffusion cell designed to perform high pressure measurements in a porous medium has been validated at atmospheric pressure. Two systems were investigated, (1) 1,2,3,4-tetrahydronaphtalene (THN) and n-dodecane (nC12), and (2) isobutylbenzene (IBB) and n-dodecane at 50% of mass fraction. Experimental results revealed an excellent agreement with benchmark values and a good agreement with theoretical data. Second, the thermal expansion and concentration expansion coefficients and the viscosity of mixtures are necessary properties for the determination of the thermodiffusion coefficient. The densities of binaries of nC12, IBB and THN for pressures from 0.1 to 20 MPa and a temperature centred on 25⁰ were measured. By an derivative method, the thermal expansion and concentration expansion coefficients were determined. Viscosities were directly measured using a high pressure high temperature viscometer. Finally, the thermosolutal convections of two ternary mixtures, methane (C1), n-butane (nC4) and n-dodecane (nC12) at a pressure of 35.0 MPa and nC12, THN and IBB at atmospheric pressure, in a porous medium, were investigated over a wide range of permeability. The effect of permeability in the homogeneous and heterogeneous porous media on fluid transport was studied with consideration of thermodiffusion and molecular diffusion. In the analysis of the homogeneous porous medium, it was found that, for permeability below 300 mD, the thermodiffusion for both mixtures was dominant; and above this level, buoyancy convection became the dominant mechanism. Also, the viscosity was found to influence the evaluation of the molecular and thermodiffusion coefficients. In the case of heterogeneous porous medium, the impact of permeability ratio on the composition of the mixture components, velocity in the porous medium and on the separation ratio was investigated. It was found that the heterogeneity of porous medium has a significant influence on the composition of the mixture components.

scholarly journals Thermal Expansion and Compressibility of Amorphous Polymers

1967 ◽  
Vol 16 (166) ◽  
pp. 504-506 ◽  
Author(s):  
Takao ISHINABE ◽  
Kinzo ISHIKAWA ◽  
Kan SHIRAKASHI
Keyword(s):  
Thermal Expansion ◽  
Amorphous Polymers
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