Polyurethanes cohesive energy

Based on the values of cohesive energies and dissociation energies of the bonds involved in the polyurethane structure, it may be possible to establish the following relative order regarding the thermal stability of polyurethanes function of the oligo-polyol structure ... 

An important point is that the percolation threshold, depends on the morphology of the percolating clustei-s, and thus on the incompatibility between the two phases. We postulate that = fgQ, so that once hard phase spheres aggregate into infinite cylinders, percolated hard phase is formed. This assumption is a crucial link that relates thermodynamic information about the hard segment (its cohesive energy density or solubility parameter) to mechanical properties of polyurethanes based on that hard segment. 

The probability of a major role of the polyester group in reaction with dip chemicals during cure is quite low. The polyurethane-polyester bond is pictured primarily as a physical interaction rather than a chemical one. Iyengar" reported that the polyurethane from methylene-few(4-phenyl isocyanate) and the epoxide have a cohesive energy density of 10.5. Polyethylene terephthalate has a cohesive energy density of 10.3. The compatibility between these two networks would be quite high and the probability exists for adhesion by the diffusion theory of Voyutskii. ... 

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