Effects of Foaming and Drainage Behavior on Structure and Properties of Polyurethane/Water Glass (PU/WG) Grouting Materials for Coal Mines

Abstract

During the grouting operation in the underground coal mine, abnormal curing behaviors such as foaming and drainage often lead to the loss of reinforcement effect of the polyurethane/water glass (PU/WG) materials on coal walls and even cause safety accidents. Herein, three kinds of PU/WG grouting materials were successfully prepared by changing the type of catalysts, which were the normal sample (C7), the foaming sample (C14), and the sample with drainage (C17) during curing. The structure, thermal stability, and compressive strength of the three samples were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry-differential thermal analysis (TG-DTA), and pressure testing machine. The results showed that the abnormal curing behavior had little effect on the thermal stability of the material, but it had a significant effect on the microstructure and compressive strength of the consolidated body. C7 exhibited a typical three-phase distribution, in which the polysilicate microspheres encapsulated by acicular carbonate were embedded in the polymer continuum. The structure of C7 had high rigidity and hardness, and the compressive strength was up to 43 MPa. The three-phase structure of C14 disappeared gradually with the increase of catalyst content, the hard block material and matrix are porous, and the compressive strength was only 2.7 MPa. The organic polymer of C17 existed in the form of microsphere and distributed irregularly in the continuum composed of inorganic components, and the compressive strength was 4.9 MPa. The abnormal solidification behavior such as foaming and drainage made the water glass/polyurethane material lose its basic mechanical properties, which cannot meet the needs of grouting reinforcement in coal mines. Therefore, the type of catalyst had a significant impact on the stability of the system, and it is necessary to avoid selecting catalysts that are likely to cause abnormal solidification during formulation research.

Study on Ratio Optimization and Diffusion-Gelation Process of Polymer Grouting Materials for Fracture Filling in Underground Mines

“…Therefore, an increasing number of researchers are concentrating on the creation and use of grouting materials made of organic polymers, particularly polyurethane materials. A one-step mixing method was used by X. Yu et al [25] to manufacture a polyurethane water glass composite grouting material. The mechanical and flame-retardant qualities of the composite grouting material are enhanced when sodium silicate is added, and the reaction temperature is also considerably lowered.…”

The Influence of Fly Ash on the Foaming Behavior and Flame Retardancy of Polyurethane Grouting Materials

“…A widely used and time-proven technique to prevent such mine accidents is to reinforce broken coal and rock by grouting, which can effectively connect and support weak structures. Currently, available grouting materials are generally classified as inorganic materials (cement [ 1 ], water glass [ 2 ], and clay [ 3 ]), organic materials (polyurethane (PU) [ 4 ], epoxy resin [ 5 ], and acrylamide [ 6 ]), and their composites [ 1 , 2 , 3 ]. Traditional inorganic materials are easy to dilute and hard to coagulate under the influence of water inrush, while the high reactive exotherm, flammability, and high cost of organic materials violate the original purpose of disaster management.…”

“…Therefore, research on grouting materials for coal mines has become an important research direction for the safety of coal mining. For example, a new soluble polymer foaming grouting material was developed by using hydrophilic amino resin as the base material [ 7 ], polyurethane/water glass (PU/WG) grouting materials [ 2 ], ordinary portland cement (C), high-strength gypsum powder (G), and a small amount of water glass (S) as matrix components to make CGS grouting material [ 8 ]. In addition, a modified grouting material was developed by using the double liquid grouting mode [ 9 ].…”