Structure Development in Flexible Polyurethane Foam-Layered Silicate Nanocomposites

Summary: Polyurethane foam nanocomposites were formed via in-situ copolymerisations, in which polyether polyol/water-montmorillonite mixtures were reacted with toluene diisocyanate. The unmodified Na⁺- montmorillonite (MMT) was swollen in polyol/water using an ultrasound technique resulting in intercalated layers with increased basal spacings of 2.3 ± 0.1 nm. Measurements of quasi-adiabatic temperature rise showed higher reaction rates as MMT loading increased from 0 to 10 wt.-%. Forced-adiabatic FTIR spectroscopy was used to determine the kinetics of both the copolymerisation and of the microphase separation between poly(ether-urethane) soft segments and polyurea hard segments. The apparent microphase-separation transition time decreased from 70 ± 3 to 42 ± 2 s upon addition of ≤10 wt.-% MMT, but at reaction times >100 s there was significant retardation of the development of hydrogen bonding in the urea groups of the hard-segment phase.