Modified basalt microfiber-reinforced polyurethane elastomer composites were prepared by a semi-prepolymer method with two different silane coupling agents (KH550 and KH560) in this study. Infrared spectroscopy was used to quantify the degree of microphase separation and analyze the formation of hydrogen bonding in polyurethane. The interfacial surface and the morphology of fibers and composites from tensile fracture were examined by a scanning electron microscope. Further measurements were performed on an electronic universal testing machine for characterizing the mechanical properties of composites. Moreover, the loss factor and transmission loss of composite materials were obtained from dynamic thermomechanical analysis and acoustic impedance tube, respectively. The suitable concentrations in the modification of basalt fibers were established at 1% for KH550 and 1.5% for KH560. The best overall performance was obtained in KH550-BMF/PUE group, as the properties increased by 31% in tensile strength, 37% in elongation at break, and 21% in acoustic insulation.

The curing kinetics of MDI-based polyurethane elastomers were studied by non-isothermal differential scanning calorimetry (DSC). The kinetic parameters of the reaction system were calculated by the Kissinger method. The changing activation energy was observed by the Flynn–Wall–Ozawa method and the Friedman method. The results of model free fitting showed that the curing reaction could be divided into two stages, showing a change in reaction order when α > 0.45 and a piecewise curing mechanism function of the MDI-based polyurethane elastomers reaction system was deduced by autocatalytic model. The extrapolation method was used to determine the optimum curing conditions for the system, which can accurately describe the curing process. In addition, the optimal curing conditions are when: the constant temperature curing temperature of the system is 81 °C, the curing time is 29 min, and the post-curing temperature is 203 °C.

Polyurethane incorporated with nanofillers such as carbon nanotubes, basalt fibers, and clay nanoparticles has presented remarkable potential for improving the performance of the polymeric composites. In this study, the halloysite nanofiller-reinforced polyurethane elastomer composites were prepared via the semi-prepolymer method. The impact of different halloysites (halloysite nanotubes and halloysite nanoplates) in polyurethane composites was investigated. Scanning electron microscopy, X-ray diffraction, infrared spectroscopy, electronic universal tensile testing, and acoustic impedance tube testing were employed to characterize the morphology, composition, phase separation, mechanical properties, and sound insulation of the samples. The composite fabricated with 0.5 wt% of halloysite nanotubes introduced during quasi-prepolymer preparation exhibited the highest tensile strength (22.92 ± 0.84 MPa) and elongation at break (576.67 ± 17.99%) among all the prepared samples. Also, the incorporation of 2 wt% halloysite nanotubes into the polyurethane matrix resulted in the most significant overall improvements, particularly in terms of tensile strength (~44%), elongation at break (~40%), and sound insulation (~25%) within the low-frequency range of 50 to 1600 Hz. The attainment of these impressive mechanical and acoustic characteristics could be attributed to the unique lumen structure of the halloysite nanotubes, good dispersion of the halloysites in the polyurethane, and the interfacial bonding between the matrix and halloysite fillers.