In view of the accidents such as rock mass breakage, roof fall and coal slide in coal mines, polyurethane/mesoscopic fly ash (PU/MFA) reinforcement materials were produced from polymethylene polyphenylene isocyanate (PAPI), the polyether polyol, flame retardant, and MFA using stannous octanate as a catalyst. 3-Glycidoxypropyltrimethoxysilane (GPTMS) was grafted on MFA surface, aiming to improve the mechanical properties of PU/MFA composites. The analyses of infrared spectroscopy and compression resistance reveal that the GPTMS can be successfully attached to the surface of MFA, and the optimum modification dosage of GPTMS to MFA is 2.5 wt. % (weight percent). On this basis, the effect of GPTMS on the mechanical properties of PU/MFA reinforcement materials during the curing process was systematically investigated through a compression test, a fracture toughness test, a three-point bending test, a bond property test, and a dynamic mechanics analysis. The results show that the compression property, fracture toughness, maximum flexural strength, and bond strength of PU/MFA composites increase by 21.6%, 10.1%, 8.8%, and 19.3%, respectively, compared with the values before the modification. Furthermore, the analyses of scanning electron microscope and dynamic mechanics suggest that the coupling agent GPTMS can successfully improve the mechanical properties of PU/MFA composites because it eliminates the stress concentration and exerts a positive effect on the crosslink density and hardness of PU/MFA composites.

The low-temperature oxidation of coal includes processes such as coal-oxygen reactions and pyrolysis. As heat generated from coal-oxygen reaction is the fundamental driver of coal spontaneous combustion, the thermokinetic studies of coal spontaneous combustion should be focused on that. However, the pyrolysis path will impact the coal-oxygen reaction, resulting in limited capability of characterizing the t accurate hermokinetic parameters of coal-oxygen reaction process. Therefore, this paper proposed a new method to test the heat generation characteristics of coal-oxygen reaction path and the theoretical model of the method was established. The experimental results show that the method can achieve successful experiments within a short period of time, and exclude the impacts from heat absorption of water evaporation and pyrolysis, and well characterize the nature of coal spontaneous combustion. Meanwhile, the thermokinetic parameters such as heat generation rate and heat production can be obtained quickly and accurately. The coal-oxygen reaction path is divided into three stages by using the heat generation characteristics. By analyzing in-situ FTIR results, it is concluded that the gradual participation of different active groups is the main reason for the three stages. There are two main factors affecting the starting and heat generation of each stage, one is the activity of active groups which can participate in the initial reaction, and the other one is the number and activity of active groups that can participate in the reaction.

Coal seam mining generates significant dust, posing serious threats to the safety of mining and the well-being of miners. This study suggests a delayed cross-linking approach to convert the dust suppressant into a gel within the coal seam, introduces a controllable slow-release ionic cross-linking dust suppressant, investigates its seepage behavior, and evaluates its dust suppression effectiveness in a coal seam. The experimental results show that the dust suppressant exhibits low viscosity and high fluidity during injection into the coal seam, facilitating effective infiltration into the seam. By managing the release rate of Ca²⁺ in the slow-release system, the gelation time of the dust suppressant within the coal seam can be controlled efficiently. While reducing the viscosity, increasing injection pressure promotes material seepage in the coal seam. The optimized injection pressure for the dust suppressant is 7 MPa, and its seepage behavior in the coal seam postinjection resembles that of water. The dust suppressant cross-links and reacts to form a macromolecular mesh structure in tiny internal pores and on the coal seam surface, enhancing the water retention and toughness of the coal seam. These combined mechanisms effectively reduce dust production during coal seam mining, achieving a source reduction of dust production.