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--- en:materialdaten:molekulargewicht [2024/07/16 16:11] – neelest
+++ en:materialdaten:molekulargewicht [2026/09/17 17:07] (aktuell) – gelöscht - Externe Bearbeitung (Unbekanntes Datum) 127.0.0.1
@@ Zeile 1: / Zeile 1: @@
-======Molecular weight======
-FIXME
-===== Molecular weight =====
-The molecular mass distribution can be characterised by the following quantities.
-The **numerical average $M_n$** is given by the following equation:
-\[M_n = \frac{\sum N_i \cdot M_i}{\sum N_i}\]
-$N_i$ is the number of molecules of group $i$ and $M_i$ is the molar mass of the respective
-group.
-The **weight average $M_w$** is defined by:
-\[M_w = \frac{\sum N_i \cdot {M_i} ^2}{\sum N_i \cdot M_i}\]
-The **polydispersity (PD)** is a measure of the width of molecular weight distribution and
-it´s the quotient of weight average and number avergage.
-\[PD = \frac {M_w}{M_n}\]
-The polydipersity is always PD ≥ 1. The higher the PD value, the broader the distribution.
-The measurement of the **solvent viscosity** or **intrinsic viscosity**
-indirectly indicates a change in the molecular mass, as the flow time of a damaged polymer is
-of a damaged polymer compared to the raw material. The
-intrinsic viscosity is linked to the molecular mass via the Mark-Houwink relationship:
-\[[η] = K \cdot \bar{M^a}\]
-$[η]$ = Staudinger index
-$K, a$ = empirically determined constants
-$ \bar{M}$ = weight average or viscosity average of the molecular mass
-The **viscosity number (VZ)** [$\frac{cm^3}{g}$] is characterised by:
-$$ VZ = (\frac {η}{η_s} - 1) \cdot \frac {1}{c} $$
-$η$ =  dynamic viscosity of the solution
-$η_s$ = dynamic viscosity of pure solvent
-$c$ = concentration in $\frac{g}{cm^3}$
-The Billmeyers intrinsic viscosity [$\frac{dl}{g}$] is calculated by:
-$$ IV = 0,25 \cdot VZ + \frac{3\cdot ln(\frac{t}{t_s})} {4\cdot c} $$
-$t$ = flow time of the solution
-$t_s$ = flow time of the pure solvent