Analysis of the build-up of polyurethane networks from toluenediisocyanate and castor oil considering intra-molecular reactions

Abstract

The build-up of polyurethane networks prepared by reacting toluenediisocyanate (TDI 80:20) with an excess of castor oil over the stoichiometric balance has been analysed using a fragment approach. This includes a kinetic scheme giving the evolution of the different species and fragments into which the network may be divided together with a recursive method to obtain statistical parameters. Intra-molecular reactions leading to the smallest cycles are taken into account in the analysis. Sol fraction and concentration of elastically active network chains in the gel fraction are estimated as a function of the stoichiometric imbalance and compared with experimental results previously reported. A reasonable fit is shown for an effective bond length in the smallest cycle equal to 0.23 nm.