Exploring Preferential Association of Laponite and Cloisite with Soft and Hard Segments in TPU-Clay Nanocomposite Prepared by Solution Mixing Technique

Thermoplastic polyurethane (TPU) is a versatile polymer exhibiting many engineering applications. In this article, two varieties of clay (Cloisite and Laponite RD) have been used to prepare TPU-based nanocomposites. They differ in, chemical composition, hydrophobicity, aggregation tendency, and dispersibility in a particular solvent. A detailed investigation of the thermal, morphological, and rheological behavior reflects the affinity of Cloisite towards the soft segment, whereas it is the hard segment for modified Laponite. The maximum improvement in onset degradation temperature has been observed to be 17.5 and 8.3 degrees C for Cloisite and Laponite, respectively. Five percent Cloisite-filled sample shows optimum storage modulus in the glassy region where as it is the 10% filled sample at the rubbery region. However, the trend remains indifferent both in rubbery and glassy regions for Laponite, and properties have been found optimum for 3% filled sample. To explore the behavior in the terminal and flow regions, dynamic rheological experiments were performed in low shear rate. Variation in dynamic rheological properties can be explained well on the basis of the combination of partly exfoliated, intercalated, and aggregated structures of the nano clay inside the TPU matrix, depending on their nature and preferential association with different segments. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2341-2354, 2008