Page 398 - Elements of Chemical Reaction Engineering Ebook

Sec. 7.3 Polymerization

I

2
g

I

0.000 20.000 40.000 60.000 80.000 100.OOO
t . (hr)

Figure 7.5 Monomer concentration as a functional time,

rate of propagation E L
' rate of propagation + rate of termination rp + r,
=
k, MR*
= k,MR'+k,SR'+k,MR'+k,CR'+k,(R*)*
Simplifying

k, M
k, M + k,M + k,C + k,S + Jm)
(7-43)
I I
In the absence of chain transfer, the monomer concentration, M, can be deter-
mined from Equation (7-43) and concentration of initiator, 12, from mation
(7-40). Consequently we have p as a function of time. We now set

to urie in the Mory distribution.
It can be shown that in the absence of termination by combination, the
mole: fractions yj and weight fraction wj are exactly the same as those far step
polymerization. That is we can determine the dead polymer concentratioi~s and
molecular weight distribution of dead polymer in free radial polymerization for
the Flory distributions. For example, the concentration of dead polymer of
chain length R is