Macromolecular Nanotechnology Detailed analysis of dynamic mechanical properties of TPU nanocomposite: The role of the interfaces Marco Aurilia a,⇑ , Filomena Piscitelli b,c , Luigi Sorrentino b , Marino Lavorgna b , Salvatore Iannace b a IMAST – Technological District on Polymeric and Composite Materials Engineering and Structures, Piazzale Enrico Fermi, 1 – 80055 Località Granatello Portici (NA), Italy b IMCB-CNR – Institute of Composite and Biomedical Materials, Piazzale Enrico Fermi, 1 – 80055 Località Granatello Portici (NA), Italy c DIMP- Department of Materials Engineering and Production – University of Naples ‘‘Federico II’’, Piazzale Vincenzo Tecchio, Napoli 80 – 80125, Italy article info Article history: Received 15 July 2010 Received in revised form 28 December 2010 Accepted 5 January 2011 Available online 19 January 2011 Keywords: Thermoplastic polyurethane Nanocomposites Microdomain morphology Dynamic mechanical properties Small angle X-ray diffraction abstract Organo-modified layered silicates (OMLSs) can largely improve mechanical properties of Thermoplastic polyurethanes (TPUs) as well as affect their microdomain morphology. Nanocomposite TPU containing OMLSs were prepared by melt blending at different con- centrations. The addition of OMLS has both induced variation in enthalpy of melting of hard and soft phases, and influenced the glass transition temperature of soft domains, as result of the microdomain phase segregation measured by means of fourier transform infrared spectroscopy (FT-IR). Small angle X-ray scattering (SAXS) analysis has shown that the mean distance between hard domains was mostly unaffected by the filler. However, its distribution broadened with the increasing concentration of the OMLSs, resulting in increased extent of the hard domain interface. The storage modulus of TPU nanocompos- ites incremented with the silicate content, while the dynamic strain scan tests showed pro- nounced non linear viscoelastic behavior. The analysis of morphological data obtained by SAXS and FT-IR measurements were correlated to thermal and dynamic mechanical prop- erties of TPU samples suggesting a crucial role of the soft domains interface. The storage modulus and loss tangent of TPU nanocomposites were found to increase with the increas- ing of the interface area of soft domains with both hard domains and OMLS stacks. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Thermoplastic polyurethane (TPU) is a block copolymer made up by alternating soft and rigid segments. The hard segments are formed by addition of a chain extender, such as butadiene diol, to the isocyanate (methylene-diphenyl diisocyanate). The soft segments consist of flexible poly- ether or polyester chains (polyols) connecting two hard segments. The soft and hard segments are incompatible at room temperature and aggregate into soft (SDs) and hard domains (HDs), respectively, resulting in a polymeric system characterized schematically by HDs formed amid the rubbery SDs [1]. However in TPU systems a third phase, the interphase between HDs and SDs, has been studies by some authors [2–4]. The driving forces for the microphase segregation are: the development of crystallinity in the hard segments, the difference in melting points, the seg- mental polarity difference, segmental length, overall com- position and molecular weight. The hard segments have a much higher melting point and polarity than the much less polar and low-melting soft segments [1]. Morphology significantly affects final properties of the TPU. In fact, the size, crystallinity and interconnectivity of the HDs, as well as the nature of domain interface and the mixing of hard segments in the soft segment phase, influence most of physical properties such as elasticity and toughness. SDs form an elastomeric matrix responsible for the elastic properties of TPUs, while HDs act as both 0014-3057/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2011.01.005 ⇑ Corresponding author. Tel.: +39 0817769241; fax: +39 0817760741. E-mail addresses: aurilia@unina.it, marco.aurilia@imast.it (M. Aurilia). European Polymer Journal 47 (2011) 925–936 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj MACROMOLECULAR NANOTECHNOLOGY