The present paper demonstrates that every pair of unreacted groups in the cross-linked network loss a canstant of 3 for the number of effective segment in the curing reaction which produces three branch cross-linking point. The cross-link density of ∑Aai-∑Bbi type curing reaction is a function of the functional density

the effective number average functionality

the ratio of number of curing agent groups to prepolymer reactive groups

the gel fraction of curing system

the extent of reaction of A (or B) groups in gel phase and the gel fraction of Aai (or Bbi)segment The last two parame-ters can not be determined directly

but can be calculated by determining the sol fra-ction and the extent of reaction of A groups and Bgroupsin sol phase.