Initiation proceeds in two stages:
a) decomposition of initiator into free radicals
I kd 2R’
b) attack by the free radical on the monomer molecule forming a monomer radical
R ‘ + M * RM ‘
If every radical from each initiator molecule reacts with a monomer molecule the rate of reaction will be given by:
Ri = 2kd[l]
where: kd is the rate dissociation constant
[I] is the initiator concentration
Usually it is not every free radical, produced by initiator decomposition, which reacts with a monomer molecule and the equation is modified to become
Ri = f2kd[l]
where: f is the initiator frequency