Kinetics and Thermophysical Properties of Polymer Nanocomposites for Solid Rocket Motor Insulation

David W.K. Ho, Joseph H. Koo*, and Ofodike A. Ezekoye
The University of Texas at Austin, Austin, TX, 78712-0292
*To whom all the correspondence should be addressed (jkoo@mail.utexas.edu)
 
Abstract

Thermal protection materials are required to protect structural components of space vehicles during the re-entry stage, missile launching systems, and solid rocket motors. Novel materials based on nanotechnology creating nontraditional ablators are rapidly changing the technology base for thermal protection systems. In this study, different polymer nanocomposite compositions were created by melt-compounded montmorillonite nanoclays or carbon nanofibers in a neat thermoplastic polyurethane elastomer (TPU) polymer using twin-screw extrusion. The kinetic and thermophysical properties that are required to analyze the ablation characteristics were measured for selective TPU materials. Properties of the nanomodified systems were then compared against the current state-of-the-art material, Kevlar®-filled ethylene-propylene-diene-monomer rubber (EPDM) as well as the neat TPU for the investigation of kinetic parameters using isoconversion technique. Based on temperatures at peak weight loss rate, Kevlar®-filled EPDM outranked the proposed formulations at all heating rates. Recognizing that ablation performance is a complex function of kinetic and thermophysical/transport properties, a surrogate test for ablation performance was investigated. Samples of neat and nanomodified thermoplastic were run in the ASTM E1354 oxygen consumption (cone) calorimeter. The peak heat release rates of the nanomodified samples were substantially less than that of the neat thermoplastic elastomer.