| Polyurethane has excellent physical and mechanical properties,water resistance,low temperature resistance,etc.It also has many polar groups in the system,which can provide high adhesive performance when used as an adhesive.Currently,two-component polyurethane adhesives have the widest range of applications due to the following advantages.Ⅰ.The formula is flexible and variable,and the scope of application is greatly increased;Ⅱ.It can be cured at room temperature or heated,and the reaction speed is faster;Ⅲ.The amount of two-component can be adjusted.In the repair work of mining machinery,there are many constraints,such as no power and small repair space.In this paper,the two-step method was used to prepare the raw materials of two-component polyurethane repair adhesive(PRA).The effects of prepolymer NCO content,thickener and filler additions on the viscosity of the two-component were investigated.The effect of the mixing unit of the static mixer on the mixing of the two-component was studied.The static mixing process was determined,and samples were prepared for relevant performance tests.The effects of soft segment polyol type,hard segment chain extender type,different chain extender compounding ratio,isocyanate index,and hard segment content on the properties of two-component PRA materials were investigated.The results are as follows(1)The NCO content of the prepolymer is 9%-12% and the addition of thickener and filler is 2%-6%,which can prepare a two-component similar viscosity system at room temperature.The two-component mixing is better when the mixing unit of the static mixer is 20.(2)The overall performance of PTMG type PRA was higher than that of PPG type PRA,and it was found that the gel time and surface drying time of DETDA type PRA were the shortest and the tensile strength was the highest when changing the type of hard segment chain extender.Changing the compounding ratio of different chain extenders showed that the gel time and surface drying time were significantly longer when the ratio of DETDA/DMTDA was changed from 100/0 to 0/100,and the tensile strength,tear strength and shear strength showed a trend of decreasing and then increasing,while the elongation at break showed a trend of increasing and then decreasing.The change of compounding ratio did not affect the heat resistance performance.The change of compounding ratio did not affect the heat resistance performance.Considering all aspects,the performance of DETDA type PRA was superior.(3)By changing isocyanate index(1.00～1.20),it can be found that the mechanical properties of PRA show enhancement and then weakening with the increase of isocyanate index,and the elongation at break gradually decreases.As the isocyanate index increases,the onset decomposition temperature of PRA increases and then decreases,the 7-d water absorption increases less,and the wear volume decreases.When R=1.15,the tensile strength and shear strength of PRA reached the maximum.When R=1.10,the tear strength of PRA reached the maximum and the heat resistance was optimal.The strength of PRA material decreased by 10%～40% after 7 d water absorption.(4)By varying the hard segment content(18%-34%),it can be found that the increase in hard segment content leads to a significant increase in the mechanical properties of PRA and a gradual decrease in elongation at break.The water absorption decreased with the increase of hard segment content,but the magnitude was small.The decrease of mechanical properties after 7 d of immersion decreased with the increase of hard section content,and the hydrolysis resistance improved.The mechanical properties,heat resistance,hydrolysis resistance and wear resistance of PRA are better when the hard segment content is 30%. |
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