Preparation of intelligent magnetic halloysite nanotubes/polyurethane nanocomposites: The role of nanotube modification on the shape recovery rate

Abstract This study aimed to investigate the effect of modification of halloysite nanotubes (HNTs) with iron oxide on the morphology and thermomechanical properties of polyurethane with shape memory behavior. Iron oxide-functionalized halloysite nanotubes (I-HNTs) were synthesized via co-precipitation method. Polyurethane nanocomposites containing 1 and 2 wt. % HNTs and I-HNTs were prepared in situ by prepolymer method. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) confirmed the successful synthesis of I-HNT. Dynamic mechanical thermal analysis (DMTA), FTIR equipped with reduced overall reflectance, atomic force microscope (AFM), and differential scanning calorimetry (DSC) showed that phase separation increased by the addition of HNTs or I-HNTs and their propensity to rigid sections. The maximum degree of micro-phase separation was 66.8% in the sample containing 2 wt. % I-HNT. In DMTA, an improvement in the shape's return speed in the shape memory behavior was observed by adding HNTs to neat polyurethane. This increase was significant in samples based on I-HNT and the highest recovery rate was 179.1 GPa.°C−1 in the sample containing 2 wt. % I-HNT. Examination of shape memory behavior showed that by adding 1 wt. % HNT, shape fixity parameter increased due to the increase in soft phase purity and shape recovery parameter decreased due to reduced mobility in the presence of HNTs. This effect was more significant in I-HNT-based samples, and the highest shape stability (96.7%) was observed in nanocomposites containing 2 wt. % I-HNT.