CONCENTRATION OF NETWORK CHAINS IN PPG-TDI-PG POLYURETHANES

Abstract

The amine degradation method for the determination of the allophanate branching point was applied to the determination of crosslinking densities in poly (oxypropylene) glycol (PPG)-2, 4-toluene diisocyanate (TDI)-propylene glycol (PG) polyurethanes. The crosslinking densities were compared with those determined from elasticity measurements and stoichiometrical considerations.
The actural chemical crosslinking densities were much smaller than those expected form stoichiometry. The permanent entanglements increased with increasing chemical crosslinkages. The physical crosslinking densities were estimated to be comparable to the chemical crosslinking densities.