Nanocomposites made from thermoplastic linear poly(urethane-siloxane) and organoclay: Composition impact on the properties

Abstract

Thermoplastic poly(urethane-siloxane)/organoclay nanocomposites (TPU NCs) with different hard segment content (20-55 wt.%) were prepared by in situ polymerization in the presence of organically modified montmorillonite as a nanofiller (Cloisite 30B; 1 wt.%). Hydroxyl-terminated ethoxypropyl-poly(dime-thylsiloxane) was used as soft segment, while 4,4'-methylenediphenyl diisocyanate and 1,4-butanediol were the hard segment components. The study of the influence of the hard segment content on the functional properties of TPU NCs was performed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffract-tometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), dynamic mechanical thermal analyses (DMTA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), water contact angle and water absorption tests. The results revealed that TPU NCs with increasing hard segment content exhibit higher values of degree of microphase separation, melting temperature of the hard segments, degree of crystallinity, storage modulus (except for TPU NC-55), but lower thermal stability and hydrophobicity. TPU NC films were hydrophobic and their free surface energy was in the range from 17.7 to 24.9 mJ m-2. This work highlights how the composition of TPU NCs would mani-pulate their functional properties and provide an additional composition handle for designing advanced TPU NC materials for special biomedical applications.