Preparation Of MDI Type Prepolymer And Effect On Properties Of Mine Reinforcement Material

In the underground mining process of coal mine,safety problems such as broken coal rock mass and roadway roof are often troubled,which seriously threaten the safety of underground construction personnel and the efficiency of coal mining.In this kind of coal seam excavation construction,it is often necessary to adopt grouting reinforcement technology and corresponding supporting measures to carry out,grouting reinforcement effect has a very important significance to ensure the construction quality and control the adverse deformation of coal seam.As a kind of early strength and efficient grouting reinforcement material,polyurethane has been widely used in coal mine construction and emergency construction.However,polyurethane material is accompanied by a large amount of chemical reaction heat release in the reaction process,which brings safety risks to the practical application.In this paper,the prepolymerization process is introduced into the B component of polyurethane reinforced material,so as to reduce the reaction temperature of polyurethane material and ensure that the material has good mechanical properties.The effects of MDI isomers and chain extenders on the properties of the materials were discussed through the prepolymerization of MDI-100 and TMP and the prepolymerization of MDI-50 and TMP/GI/EG.By means of infrared spectrum analysis,GPC,thermogravimetric analysis,oxygen index instrument,electronic universal testing machine and other experimental means to explore the relationship between molecular structure and reinforcement materials.The main research contents are as follows:(1)Explore the relationship between the reaction rate and the viscosity and molecular weight of the prepolymer during the prepolymerization process of MDI-100/MDI-50 and TMP at different temperatures.As the temperature increases within the range of 50-80 ℃,the reaction rate accelerates,the viscosity of the prepolymer increases,and the content of polymer with high molecular weight in the prepolymer increases.The viscosity of MDI-50+TMP prepolymer prepared at 80℃was 2019 m Pa.s,the reaction setting time was 64 s,the highest reaction temperature was 99.7℃,the tensile strength was 48.89 MPa,and the tensile strength was 4.79 MPa.(2)Through the analysis of the NCO content change,viscosity,molecular weight distribution and infrared spectrum of the prepolymer,it is found that the steric hindrance effect of 2,4 ’-MDI in MDI-50 makes the comprehensive performance of the materials prepared by the prepolymer better than that of MDI-100.It is more suitable for preparing prepolymers.(3)GI and EG were used as chain extenders to conduct prepolymerization experiments with MDI-50 to explore the influence of diol chain extender and ternary alcohol chain extender on materials.It is found that GI as a chain extender forms more types of polymers and has a higher degree of crosslinking,which makes the mechanical properties of reinforced materials better than the prepolymers prepared by EG as a chain extender.The compressive strength of the reinforced material prepared by GI chain extender increases with the increase of prepolymerization temperature,while the reinforcement material prepared by EG as chain extender shows the opposite trend.