Structure and properties of flexible polyurethane foams with nano- and micro-fillers

The feasibility of using mineral nano- and micro-fillers as replacement of copolymer polyols in flexible foams was examined. Nano-fillers were nano-clays, a natural montmorillonite (Cloisite Na(+)) and montmorillonite modified with an organic quaternary ammonium salt (Cloisite 10A), and nano-silica dispersed in methylethylketone. Micro-fillers were micronized clay and silica. Flexible foams were prepared from the ethylene oxide caped polyether triol and toluene diisocyanate with water as the chemical blowing agent. All foams had good morphology except those with nano-clay. The open cell content was above 95%, but air flow was very low in all samples. Micro-fillers did not significantly change cell structure and morphology of hard domains. They moderately increased density, hardness, compression strength, and compression set and decreased elongation at break. The other properties were not affected. Cloisite Na(+) (non-treated montmorillonite) and nano-silica with a hydrophilic surface increased hardness, compression strength, and rebound resilience of the foams, whereas Nano-clay 10A (surface-treated montmorillonite) decreased the modulus, hardness, and compression strength. Tensile and tear strengths decreased with the addition of nano-clay fillers, but increased with nano-silica.