Effects of organically modified nanoclay on structure and mechanical properties of flexible polyurethane foams

Flexible polyurethane (PU)/organically modified nanoclay (organoclay) nanocomposite foams were synthesized by in situ polymerization and foam samples were prepared by a batch process. X-ray diffraction, scanning electron microscopy and tensile and compression tests have been used in order to investigate clay dispersion, cell morphology, tensile properties and dimensional stability, respectively. XRD patterns of PU/nanoclay (2% by weight) reveal good clay dispersion and exfoliation. The presence of clay results in an increase in cell density and a reduction of cell size compared to pure PU foam and the amount of the changes of the both properties are proportional to the amount of clay loading. Furthermore, addition of clay leads to an increase in tensile modulus and a reduction in elongation at break of the PU foams which are both proportional to the amount of clay present in the nanocomposite foam. The results obtained from the compression tests prove that dimensional stability and rate of recovery of PU foams reduces in the presence of clay. The results obtained from the mechanical studies could be attributed to the grafting of PU molecules on to the clay surface through the reaction between the -NCO groups of PU molecules and the -OH groups on the clay.

Keywords:

nanocomposite foam , cellular morphology , montmorillonite