Preparation and structure analysis of aluminum oxide/water glass/polyurethane composite grouting material for mining

In order to achieve safer and more efficient coal mining, the utilization of water glass/polyurethane (WG/PU) composite grouting material has become widespread in treating fractured coal mining faces. The reaction temperature and mechanical properties of WG/PU are crucial considerations that significantly impact safety and reinforcement effectiveness. However, reducing the reaction temperature without compromising the material's mechanical properties poses a challenge with conventional modification methods. Therefore, this study presents the development of a novel hybrid grouting material, namely Al2O3-WG/PU, which incorporates thermally conductive aluminum oxide (Al2O3) into WG/PU. The response surface method was employed to investigate the effects of key factors such as modules, mass ratio, Al2O3 content, and plasticizer content on the reaction temperature and compressive strength. Additionally, the static and dynamic compression properties of Al2O3-WG/PU were measured and analyzed. The morphology, elemental distribution, chemical composition, and valence information of the composite materials were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the introduction of A2O3 and scientific formula design reduces the maximum reaction temperature of Al2O3-WG/PU by 14.9 °C (12.7%). Although the percentage reduction may not seem significant, it represents substantial progress in the field of coal mine grouting materials. Moreover, this modification method not only maintains the material's mechanical properties but also enhances its compressive strength by 13.84 MPa (27.3%). Based on the characterization results, this study proposes a mechanism for temperature reduction and strength enhancement. The hybrid composite materials produced from Al2O3 and WG/PU show lower reaction temperatures and improved mechanical properties, presenting a promising solution for improving the safety performance of coal grouting materials.