486 Research Article Received: 12 January 2009 Revised: 22 June 2009 Accepted: 16 July 2009 Published online in Wiley Interscience: 27 November 2009 (www.interscience.wiley.com) DOI 10.1002/pi.2726 Nanofilled polyols for viscoelastic polyurethane foams Lorenzo Indennidate, Donato Cannoletta, Francesca Lionetto, Antonio Greco ∗ and Alfonso Maffezzoli Abstract The use of polyether polyols is common in polyurethane industry, particularly in soft PU applications. In particular, viscoelastic foams, characterized by slow recovery after compression, are obtained using poly(ethylene oxide) (PEO) polyols. Nanofilled polyols can be used for the production of viscoelastic foams with improved fire resistance properties. The high polarity of polyether polyols is responsible of a poor affinity with the organic modifiers used in commercial organically modified montmorillonite (omMMT). In this work, organically modified montmorillonites were prepared, having an improved affinity with the polyether polyols used for the production of soft PU foams. The montmorillonite was modified by using polyetheramines with different ethyleneoxide/propyleneoxide amounts. A strongly intercalated/exfoliated structure was obtained after mixing the polyol with the omMMT. The viscosity increased by three orders of magnitude and the diffraction angles of the MMT measured by x-ray analysis decreased to values lower than 1.5 ◦ . The intercalated structure was preserved after the curing stage, when the isocyanate was added to the polyol/omMMT. The resulting polyurethane had an irregular open cell structure, and was characterized by a mechanical properties comparable to those of unfilled polyurethane. c  2009 Society of Chemical Industry Keywords: nanocomposite; polyurethane; foam INTRODUCTION In recent years, polymer/clay nanocomposites have attracted increasing academic and industrial interest. This is because of the potential for significant enhancement in mechanical properties, combined with reductions in permeability and flammability, resulting from the incorporation of only a few weight percent of a nanoscale lamellar filler into a polymer. 1 Thermoset-based polymer/clay nanocomposites are commonly prepared by in situ intercalation/exfoliation, including two stages: mixing of the oligomer or monomer with the clay followed by the polymerization. Intercalation and/or exfoliation can occur during the mixing stage or during the polymerization stage, due to the formation of a crosslinked structure interpenetrated among the clay lamellae. Exfoliation obtained during the mixing stage presents some advantages compared with exfoliation obtained during the polymerization step: (i) it provides a better control of the degree of exfoliation and (ii) it is easier to evaluate whether the material is exfoliated before the formation of the products. 2 Typically, organically modified montmorillonite (omMMT), produced via ion-exchange reactions with cationic surfactants, is used to form polymer/clay nanocomposites. The organic modification of the nanofiller is necessary in order to promote exfoliation. The aim of this modification is to increase the capability of monomers or polymer chains to diffuse (intercalate) into the interlayer spacings, swelling the layered structure to form intercalated or exfoliated lamellar stacks. 3 The use of polyether polyols is common in the polyurethane (PU) industry, particularly for soft PU applications. In particular, viscoelastic foams, characterized by slow recovery after com- pression, are obtained using poly(ethylene oxide) (PEO) poly- ols. The high polarity of polyether polyols is responsible for a poor affinity with the organic modifiers used in com- mercial omMMT. As a consequence of this, poorly interca- lated structures are usually obtained. 2,4,5 The use of high- polarity modifiers causes an improved compatibility with the polyether polyols, and highly exfoliated structures can be obtained. 3,6–8 The aim of the work reported here was the production of PU nanocomposites based on the use of polyetheramines as organic modifiers for Na + MMT. Exfoliation was obtained during the mixing stage of the polyol and the omMMT. The formation of a strongly intercalated and/or exfoliated structure was evidenced by wide-angle XRD and rheological analysis. The results obtained were compared with those obtained using commercial MMT, with and without organic modifier. The intercalated structure is preserved after the curing stage, when isocyanate is added to the polyol/omMMT. The resulting PU has an irregular open- cell structure, and is characterized by a higher flame resistance compared to unfilled PU. ∗ Correspondence to: Antonio Greco, Department of Innovation Engineering, University of Salento, Via Monteroni, 73100 Lecce, Italy. E-mail: antonio.greco@unile.it Department of Innovation Engineering, University of Salento, Via Monteroni, 73100 Lecce, Italy Polym Int 2010; 59: 486–491 www.soci.org c  2009 Society of Chemical Industry