Understanding phase separation and morphology in thermoplastic polyurethanes nanocomposites

Carbon nanotubes (CNTs) can be effective in influencing the hard domain (HD) and soft domain (SD) morphology in thermoplastic polyurethanes (TPU), and their combination with cellulose nanocrystals (CNCs) can maximize these effects in TPU composites. Atomic force microscopy (AFM) indicated that TPU morphology exhibits multi-scale phase separation characterized by heterogeneous morphologies at the micro-and nano-scales. CNTs appear to preferentially aggregate in the HD regions, favoring the nucleation and growth of smaller and more distributed HD spherulites, while thermal analyses confirmed a significant changes in the crystallization behavior of TPU nanocomposites. Scanning electron microscopy (SEM) analyses performed on TPU nanocomposites prepared by in-situ polymerization and compression molding suggested that incorporation of a small amount of CNCs can have a positive effect on CNT dispersion and favor a more homogeneous distribution. (C) 2016 Elsevier Ltd. All rights reserved.