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influential observations, influence function, influence on the subspace spanned by eigenvectors, principal factor analysis, perturbation theory of eigenvalue problems,

Gel points are investigated as the critical extent of reaction at gelation by FT-IR and viscoelastic measurements for the network formed by the epoxy–amine system. The reaction systems examined are comprised of diglycidyl ether of bisphenol A (DGEBA) and polyoxypropylene (POP) diamine of different chain lengths with various degrees of dilution. The experimental results are obtained as the delay of gel point, that is the delay from the gel point expressed by the Flory–Stockmayer formula, and interpreted in terms of ring formation caused by intramolecular reaction which is characterized by the ring forming parameter of λ0. This parameter relates with the internal concentration (in mol L–1) of reactive groups P ab, for RA fa + R′B fb type polymerization. The analyses of the conversion curve (p vs t curve, where p denotes the extent of reaction) obtained by FT-IR measurement are carried out on the basis of the kinetic model of the epoxy-amine reaction to find the ratio of rate constant. For all the reaction systems, gelation occurs in excess of Flory–Stockmayer gel point; the excesses are 0.09–0.15 in extent of reaction. λ0 is determined from the gel point data through the p c–λ0 relationship developed in the first part of this study, where the schemes of unequal reactivity and the states of reaction for POP diamine unit are incorporated. The gel point data are also applied to the p c–λ0 relationship where these schemes are not incorporated. Following λ0, P ab and the length of bond are derived and compared in terms of the effect of difference in these schemes.