| In recent years,modified emulsified asphalt has been widely used in road construction and maintenance,the commonly used modifiers for preparing modified emulsified asphalt include styrene-butadiene-styrene block copolymer(SBS),polymerized styrene butadiene rubber(SBR),polyurethane(PU)and epoxy resin(EP),there are still some problems in the preparation and practical application of each polymer in emulsion.In view of this,this study aims to combine the performance of polyurethane and epoxy resin,and overcoming the shortcomings of pure polyurethane or epoxy resin modified emulsified asphalt.A polyurethane epoxy composite emulsion was independently developed as a modifier of emulsified asphalt,and the performance of modified emulsified asphalt was studied:Firstly,the preparation process of cationic aqueous polyurethane was explored.Polytetrahydrofuran glycol(PTMG),diphenylmethane diisocyanate(MDI),castor oil(CO)etc.are used as raw materials,and the effects of four main influencing factors,namely R value(-NCO/-OH),neutralization degree,CO addition amount,and the addition amount of hydrophilic chain extender MDEA,on the preparation process and performance were investigated through orthogonal experiments.By testing the stability,particle size,viscosity of the emulsion and the mechanical properties,thermal properties,water resistance of the film,the effects of various factors on the properties of the waterborne polyurethane emulsion and film were analyzed.The results showed that the amount of MDEA added has a significant impact on the stability of polyurethane emulsion and the water absorption of the adhesive film,and the R value has a significant impact on the mechanical properties of the polyurethane adhesive film.It was proved by infrared test that carbamate was formed in the synthesized molecular chain,and waterborne polyurethane emulsion was successfully obtained after emulsification.Then with bisphenol type A epoxy resin as the modifying agent,based on the synthesis process of cationic aqueous-polyurethane.The effects of epoxy resin modification process,epoxy resin types,and epoxy resin content on the performance of composite emulsion were explored,and the preparation process of waterborne polyurethane modified by epoxy resin was determined.The stability,particle size,viscosity,mechanical properties,thermal properties and water resistance of the film of a series of composite emulsion with different ratios were tested and analyzed,and finally a high-performance polyurethane epoxy composite emulsion was synthesized.The results showed that the addition of epoxy resin improved the mechanical properties and water resistance of polyurethane,with a tensile strength of 28.7 MPa,a water absorption rate of 3.75%,and a certain improvement in thermal properties.Finally,the homemade polyurethane-epoxy compound emulsion was used to modify the emulsified asphalt,the modification process was determined,the epoxy curing scheme was explored,and the influence of polyurethane epoxy composite emulsion with different content on the performance of modified emulsified asphalt was studied.The curing plan of epoxy resin was determined through mechanical performance testing,including the selection of curing agent,curing ratio,and determination of curing time;The conventional performance and thermal performance test results of modified emulsified asphalt with different dosages indicate that the high-temperature performance of modified asphalt has been significantly improved;Observe the dispensability of the modifier in emulsified asphalt using a fluorescence microscope,when the dosage is ≤ 20%,the modifier is evenly dispersed;Through infrared spectrum analysis,it was found that physical modification and chemical modification existed simultaneously in polyurethane epoxy composite emulsion modified emulsified asphalt;Through TGA and DSC analysis,it was found that the thermal stability of modified emulsified asphalt was improved to a certain extent.The above results showed that polyurethane epoxy composite emulsion has excellent modification effect on emulsified asphalt,and has great application value in asphalt pavement construction and maintenance. |
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