Temperature and Pressure Dependence of the Free Volume in Polyisobutylene from Positron Lifetime and Pressure-Volume-Temperature Experiments

2006 ◽  
Vol 207 (8) ◽  
pp. 721-734 ◽  
Author(s):  
Duncan Kilburn ◽  
Jan Wawryszczuk ◽  
Günter Dlubek ◽  
Jürgen Pionteck ◽  
Rüdiger Häßler ◽  
...  
Keyword(s):  
Free Volume ◽  
Pressure Dependence ◽  
Positron Lifetime ◽  
Temperature And Pressure

scholarly journals The Temperature and Pressure Dependence of the Free Volume in Fluoroelastomers from PALS and PVT Experiments

2005 ◽  
Vol 107 (4) ◽  
pp. 685-689 ◽  
Author(s):  
G. Dlubek ◽  
A. Sen Gupta ◽  
J. Wawryszczuk ◽  
D. Kilburn ◽  
J. Pionteck ◽  
...  
Keyword(s):  
Free Volume ◽  
Pressure Dependence ◽  
Temperature And Pressure

High-Pressure Dependence of the Free Volume in Fluoroelastomers from Positron Lifetime andPVTExperiments

2005 ◽  
Vol 38 (2) ◽  
pp. 429-437 ◽  
Author(s):  
Günter Dlubek ◽  
Jan Wawryszczuk ◽  
Jürgen Pionteck ◽  
Tomasz Goworek ◽  
Harald Kaspar ◽  
...  
Keyword(s):  
High Pressure ◽  
Free Volume ◽  
Pressure Dependence ◽  
Positron Lifetime

An Application of a Free Volume Model to Lubricant Rheology I—Dependence of Viscosity on Temperature and Pressure

1984 ◽  
Vol 106 (2) ◽  
pp. 291-302 ◽  
Author(s):  
S. Yasutomi ◽  
S. Bair ◽  
W. O. Winer
Keyword(s):  
Free Volume ◽  
Pressure Dependence ◽  
Pressure Effects ◽  
Mineral Oils ◽  
Volume Model ◽  
Free Volume Model ◽  
Synthetic Lubricants ◽  
Temperature And Pressure ◽  
Lubricant Viscosity ◽  
Dielectric Transition

Analyses of the dependence of lubricant viscosity on temperature and pressure, μ(T,P), have been carried out by using a modified WLF equation in which pressure effects on viscosity are given in terms of the pressure dependence of the glass transition temperature, Tg, and of thermal expansivity of free volume, αf. logμ(T,P)=logμg−C1•(T−Tg(P))•F(P)C2+(T−Tg(P))•F(P) where C1 and C2 are well known WLF constants, and μg is a viscosity at Tg. Tg(P) and F(P) are functions for describing the pressure dependence of Tg and αf, respectively. On the basis of the iso-viscous concept for Tg(P), μg has been assumed to have a constant value, 1 TPa•s, at any pressure (SCHEME I). SCHEME I yields a reasonable variation in Tg and αf with pressure for synthetic lubricants, while this analysis suggests a lower μg for mineral oils. In order to improve the applicability of the free volume model, a reference temperature Ts(P), at which the viscosity is 10 MPa•s, has been introduced instead of Tg(P) (SCHEME II). Analyses of dielectric transition for some lubricants and of μ(T,P) in the ASME Pressure-Viscosity Report have confirmed the excellent applicability of the present free volume model over wide ranges of temperature and pressure.

Measurements of real non-Newtonian response for liquid lubricants under moderate pressures

2001 ◽  
Vol 215 (3) ◽  
pp. 223-233 ◽  
Author(s):  
S Bair
Keyword(s):  
Numerical Simulation ◽  
Kinetic Theory ◽  
Simple Shear ◽  
Pressure Dependence ◽  
Shear Stresses ◽  
Current Interest ◽  
Flow Properties ◽  
Power Law Fluid ◽  
Temperature And Pressure

A thorough characterization of all viscous flow properties relevant to steady simple shear was carried out for five liquid lubricants of current interest to tribology. Shear stresses were generated to values significant to concentrated contact lubrication. Two types of non-Newtonian response were observed: shear-thinning as a power-law fluid and near rate-independence. Functions and parameters were obtained for the temperature and pressure dependence of the viscosity and of the time constant for the Carreau-Yasuda equation. Results are consistent with free volume and kinetic theory, but directly contradict many assumptions currently utilized for numerical simulation and for extracting rheological properties from contact measurements.

Mechanical and microstructural properties of polystyrene based composites: positron lifetime spectroscopic and DSC studies

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Abdullah Mohammed Ali Mohammed Altaweel ◽  
Jaya Madhu Raj ◽  
Malalvalli Nagarajaiah Chandrashekara ◽  
Puttegowda Ramya ◽  
Parthasarathy Sampathkumaran ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Free Volume ◽  
Positron Lifetime ◽  
Tensile Modulus ◽  
Silica Content ◽  
Scanning Calorimetry ◽  
Dsc Studies ◽  
Microstructural Property ◽  
Calcium Aluminosilicate

Abstract Polystyrene (PS) based composites respectively with cenosphere (CS) and calcium aluminosilicate (CAS) as fillers were studied using the positron lifetime technique to reveal the correlation between free volume, a microstructural property, and mechanical properties of the composites (tensile strength and tensile modulus). The thermal stability of the composites was determined using differential scanning calorimetry. The results showed that addition of CAS filler lead to a significant improvement in the mechanical properties of the composite, whereas addition of CS resulted in improvement in tensile modulus only. Both PS/CAS and PS/CS composites showed enhancement in thermal stability compared with that of the pure PS matrix. The positron results showed that the average free volume size for the PS/CAS composite (at 40 phr CAS) was reduced significantly compared with that of the pure PS. These results are understood in terms of the influence of silica content, filler-matrix interaction, and particle size.

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