Thermoresponsive polyurethane (PU)-silica nanocomposites were synthesized by incorporating silica particles as multifunctional cross-linkers into the PU via sol-gel reactions. At 2 wt% silica, the composites showed over 99% shape fixity and shape recovery up to the 4th thermomechanical cycle along with outstanding mechanical properties in their rubbery as well as glass state. The incorporated nano-sized silica particles gave dual effects of multifunctional chemical cross-links and reinforcing fillers. The properties were favorably compared with those of uncross-linked PU and conventionally cross-linked PU
Polyurethane flexible foam having shape memory effects has been synthesized from polyester polyol
and 4,4′-diphenylmethane diisocyanate (MDI) following the quasi-prepolymer method in the
presence of water as the blowing agent, and the effect of the organometallic catalyst and
the molecular weight of polyol has been studied. It was found that the closed cell content,
foam density, rubbery modulus, compression set, and shape fixability increased with
increasing amounts of organometallic catalyst and decreasing molecular weight of polyol,
whereas the cell size showed the opposite tendency. On the other hand, the shape
recoverability of the foam was over 99% regardless of the catalyst content and molecular
weight of polyol.
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