Melamine (M), phenol (P) and formaldehyde (F) were used as raw materials to synthesize a melamine–phenol–formaldehyde resin (MPF) which was used as shell material to prepare a self-healing microcapsule with E-51 epoxy resin as the core, via in situ polymerization. Fourier transform infrared spectroscopy, environmental scanning electron microscopy and laser particle size analysis were used to characterize the surface morphology, structure and properties of the microcapsule. The influence of the reaction conditions on the properties of the microcapsule was investigated by orthogonal testing. The mass ratio between the MPF shell and the epoxy resin core was found to be 1.2:1.0, optimum pH for shell formation was found to be 3, the emulsification speed was 800 r/min, the acidification speed was 400 r/min and the acidification temperature was 60°C. Under these conditions, the prepared microcapsules are regular and spherical with a smooth, dense surface and uniform particle size with a normal distribution. The microcapsules remained well dispersed and did not aggregate. The orthogonal test revealed that the average particle size and yield of the microcapsules are mainly determined by the core/shell mass ratio, whereas the reaction temperature had a greater impact on the core content of the microcapsules. Although the best microcapsule samples showed poor anti-permeability in ethanol, they exhibited good thermal, isothermal and storage stabilities. This indicates that they may be stored at a constant temperature.

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.