A Simplified Method for the Estimation of Hole Free Volume Fraction from the Specific Volume

A brief introduction in the equation of state of the Simha-Somcynsky hole theory is presented. This theory allows to calculate the volume fraction h of free volume holes from pressure-volume-temperature experiments. These holes are detected by ortho-positronium and from the value of h and the mean ortho-positronium hole size the hole density may be calculated. We discuss a simplified method to estimate h which makes use of the relation V* = 1.52 $V_W$ between the scaling volume V* of the Simha-Somcynsky hole theory equation of state and the van der Waals volume $V_W$. Moreover, we present a new simplified method for the estimation of h which starts with the Schottky (Arrhenius) equation for the concentration of thermal vacancies and makes use of a linear relation between the scaling temperature T* and the hole formation enthalpy $H_h$, $H_h$(kJ/mol)=6.54×$10^{-4}$T*(K)

A Simplified Method for the Estimation of Hole Free Volume Fraction from the Specific Volume

A brief introduction in the equation of state of the Simha-Somcynsky hole theory is presented. This theory allows to calculate the volume fraction h of free volume holes from pressure-volume-temperature experiments. These holes are detected by ortho-positronium and from the value of h and the mean ortho-positronium hole size the hole density may be calculated. We discuss a simplified method to estimate h which makes use of the relation V* = 1.52 $V_W$ between the scaling volume V* of the Simha-Somcynsky hole theory equation of state and the van der Waals volume $V_W$. Moreover, we present a new simplified method for the estimation of h which starts with the Schottky (Arrhenius) equation for the concentration of thermal vacancies and makes use of a linear relation between the scaling temperature T* and the hole formation enthalpy $H_h$, $H_h$(kJ/mol)=6.54×$10^{-4}$T*(K)

Membrane properties of microporous structures prepared from polyethylene/polymethacrylate IPN

10.1002/app.12414Journal of Applied Polymer Science8971976-1982JAPN

Effect of surfactant and radiation treatment on the morphology and properties of PP/EG composites

The effects of surfactant and electron beam (EB) radiation treatment on the morphology and properties of polypropylene (PP)/expanded graphite (EG) composites were investigated. Surfactant treatment and sonication of EG before mixing with PP significantly influenced the morphologies of the composites, and the modification of EG with sodium dodecyl sulphate (SDS) had a strong negative influence on the electrical conductivities of these composites. The electrical percolation concentration is shifted from 5 to 6 wt% filler to about 10 wt% filler in the presence of SDS. The melting and crystallization temperatures of PP in the composites were not affected by surfactant or EB radiation treatment. There were small differences in PP crystallinity, depending on the type and combination of treatments. The filler particles acted as nucleating agents and the crystallization temperatures shifted to higher temperatures. The thermal stability of PP was significantly higher after irradiation, and improved even further for the samples containing EG, but the presence of EG had little influence on the thermal stabilities of the non-irradiated composites. For both non-irradiated and irradiated composites the maximum tensile stress and elongation at break values are lower than the neat matrix, while the tensile modulus increased significantly.National Research Foundation of South Africa (UID 73982) and the International Bureau of the BMBF in Germany (project SUA 10/009)

Highly conducting poly(methyl methacrylate)/carbon nanotubes composites: Investigation on their thermal, dynamic-mechanical, electrical and dielectric properties

International audienceNanocomposites of poly(methyl methacrylate) (PMMA) containing various multi-walled carbon nanotubes (MWCNT) contents were prepared using melt mixing. Several techniques were employed to study the influence of the MWCNT addition on the thermal, mechanical, electrical and dielectric properties of the PMMA matrix. The electrical percolation threshold () was found to be 0.5 vol.% by performing AC and DC conductivity measurements. Significantly high conductivity levels () were achieved: exceeds 10 S/cm already at 1.1 vol.%, the criterion for EMI shielding ( > 10 S/cm) is fulfilled at 2.9 vol.%, and the highest loaded sample (5.2 vol.%) gave a maximum value of 0.5 S/cm. Dielectric relaxation spectroscopy measurements in broad frequency (10−10 Hz) and temperature ranges (-150 to 170 °C) indicated weak polymer-filler interactions, in consistency with differential scanning calorimetry and dynamic mechanical analysis findings. Weak polymer-filler interactions and absence of crystallinity facilitate the achievement of high conductivity levels in the nanocomposites