Functionality weight-average

To determine (fw)A from Eq. (2.3), one must know the weight-average functionality (fw)B of the cross-linking reagent, the Ao/B0 ratio and the conversion at the gel point (PA or PB). The gel point is usually determined from viscosity changes of the reaction system. 

This assumption is equivalent to the statement that each FU has an equal chance to undergo cyclization. Given the random distribution assumption, the distribution of M, is then the binomial one. Now it is easy to find the mean functionalities ( ) which can be put equal to the weight average functionality defined by M LifiMi [85-89]. Let // be the mth moment. The mean functionality is calculated via... 

Flory Fgel=l/K/a-l)(/b-l)] yi, and are the weight-average functionalities of molecules with reactive groups of types a and b (Macosko and Miller, 1976). 

Flory Rgel — l/(J5pwO 1) — Z)p o is the initial weight-average functionality of starting polymer chains Df o is the initial number-average functionality of starting polymer chains (Miller et al, 1979). 

Figure 9.30 Weight average functionality versus weight average molecular weight for HTPB fractions.

The number- and weight-average functionality of the primary molecules are then... 

Where f is the weighted average functionality of end-linker and f, that of (4). 

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