Unterschiede

Hier werden die Unterschiede zwischen zwei Versionen angezeigt.

--- en:grundlagenhandbuch:materialkenngroessen:gefuellte_polymere:porositaet [2026/01/26 20:20] – deppe2
+++ en:grundlagenhandbuch:materialkenngroessen:gefuellte_polymere:porositaet [2026/01/27 12:47] (aktuell) – gelöscht deppe2
@@ Zeile 1: / Zeile 1: @@
-====== Porosity [3] ======
-===== Porosity [3] =====
-Porosity is defined using the ratio of void volume to total volume:
-$$\psi = \frac{V_H}{V_{ges}} \tag{1}$$
-with:
-  * ψ = porosity,
-  * VH = void volume,
-  * Vges = total volume.
-The porosity can differ by the look of the agglomerate without being recognized. In the figure different types of pores are shown in the model of a single particle.
-There are open and closed pores, pores with a fixed diameter, pores, which continually taper, and pores, which are only accessible over narrow capillaries, as well as through flow pores. Surface roughness must be considered.
-The porosity of single particles ψp is due to pores. From a cluster of particles one gets the agglomerate porosity ψa. This is the relationship of the void volume between the particles to the agglomerate volume. The problem with this definition is the specification of the agglomerate volume with respect to the outer zones.
-In the loose fill of agglomerates one can find the bulk porosity ψb, which is the relationship between the agglomerates and the total volume of the loose fill within the mold cavity. The total porosity is composed of individual porosities. It considers:
-$$(1 - \psi) = (1 - \psi_p)(1 - \psi_a)(1 - \psi_b) \tag{2}$$
-{{ :en:grundlagenhandbuch:materialkenngroessen:gefuellte_polymere:en_sigma150_dlg_grundlagenhandbuch_materialkenngroessen_031.svg?800%nolink |}}
-**Figure:** Porosity of a) single particles, b) bulk [5]
-From measurements one cannot not distinguish between the porosity of the primary particles ψp, the porosity of the agglomerates ψa and the bulk porosity ψb. Densities are also usually measured. A porous material has a smaller density than the solid material ρf . The density of the individual particle ρp is related to the porosity as follows:
-$$\rho_p = (1 - \psi_p) \cdot \rho_f \tag{3}$$
-The agglomerate density is:
-$$\rho_a = (1 - \psi_p) \cdot (1 - \psi_a) \cdot \rho_f \tag{4}$$
-Appropriately considered for the bulk density rp:
-$$\rho_b = (1 - \psi_p) \cdot (1 - \psi_a) \cdot (1 - \psi_b) \cdot \rho_f \tag{5}$$
-Besides the different pore types there are also various pore sizes to be considered. In the figure, the distribution density curve of the pore radius is represented for a fill of agglomerates. Generally speaking, pore sizes can be distinguished into: single particle pores, agglomerate pores and loose material pores. In the ideal case they yield various maximums of the distribution density (multi-modal).
-{{ :en:grundlagenhandbuch:materialkenngroessen:gefuellte_polymere:en_sigma150_dlg_grundlagenhandbuch_materialkenngroessen_032.svg?600%nolink |}}
-**Figure:** Schematic cell diameter distribution [5]
-In the determination of the porosity of the agglomerates or the individual particles, there are a range of measuring techniques at ones disposal. Mentioned here are the figure analysis and the mercury porosity techniques.