Rheological and thermal properties of glycidyl azide polyol‐based energetic thermoplastic polyurethane elastomers

The purpose of this study was to investigate the effects of polyol on glycidyl azide polyol (GAP)‐based energetic thermoplastic polyurethane elastomers (ETPEs). Briefly, a series of GAP/polyol‐based ETPEs (GAP/polyol ETPEs) with different copolyol ratios and hard segment contents were synthesized using GAP‐diol with common polyol and 4,4‐methylenebis(phenylisocyanate)‐extended 1,5‐pentanediol as soft and hard segments, respectively, by solution polymerization in dimethylformamide. The three types of polyols used were poly(tetramethylene ether) glycol (PTMG), polycarbonate‐diol (PCL‐diol) and polycaprolactone‐diol (PCD‐diol). The synthesized GAP/polyol ETPEs were identified and characterized using Fourier transform infrared and ¹H NMR spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rheometric mechanical spectrometry. For GAP/PCL ETPEs with lower hard segment content, DSC results showed that the GAP segment failed to interact with either the PCL segment or PCL melting. In addition, the results of DMA showed that the presence of PCL segments in ETPEs improved the storage modulus below the melting temperature of the PCL block. Further, the crystalline PCL segments were attributed to reinforcing the ETPEs in a manner similar to that of the hard domain. As the hard segment content increased in the GAP/polyol ETPEs, both GAP/PTMG ETPEs and GAP/PCL ETPEs exhibited microphase separation transitions, while rheological experiments demonstrated a sudden decrease in complex viscosity in neighboring microphase separation transitions. © 2012 Society of Chemical Industry