| With merits of lower-price, wide-accessibility, strong bonding-strength,ability to cure at low temperature, tiny shrinkage rate, good mechanicalproperties, higher heat and chemical stability, Epoxy Resin(EP) grouting is thepreferred material in the crack repair of concrete construction. However, theweaknesses of brittleness, low tensile-strength, difficulty in moisture curing andpoor adhesion performance in underground’s humid environment constrain itsapplication in subway mend. Meanwhile, incorporation of polyurethane intoepoxy resin networks to prepare Polyurethane/Epoxy resin interpenetratingpolymer netwoks (PU/EP IPNs) is one of the focuses in the EP toughingmodification research field in the recent years. And a number of significantadvancements have been achieved, even some of these accomplishemts havesuccessfully been used in practical utilization, such as electronicpotting materials, adhesives, coatings and so forth. But there is few studiesattempting to apply PU/EP IPNs to grouting material. Thus, based on the groundof molecular design, the present work synthesized PU-prepolymer with certainamount of molecular weight through studing factors affecting synthesis of PU, then the PU-prepolymer was incorporated into EP netwoks to form a new kindof grafted PU/EP IPNs grouting; Finally, Effects of composite curing agent’sratio and content, diluent’s dosage and promoter on mechanical and workingproperties of grafted PU/EP IPNs grouting were investigated. The majorcontents are listed as follow:PU-prepolymer was synthesized with toluene diisocyanate (TDI) andpolyethylene glycol (PEG) as raw materials, factors affecting the synthesizing ofPU-prepolymer were studied: dehydration conditions of PEG, addition methodsof raw materials, reaction temperature and time; and optimal synthesisconditions of PU-prepolymer was obtained: PEG should be dehydrated under115°C,0.085MPa of vacuum degree and4h; reaction temperature is within75~80℃and2.5~3.0h of reaction time. Infrared spectra(FT-IR) indicates thatthe product is PU-prepolymer.Grafted PU/EP IPNs was prepared with PU-prepolymer and EP as rawmaterials, then various additives were added to form grafted PU/EP IPNsgrouting. Effects of Isocyanate index(R) and content of PU-prepolymer onmechanical and thermal properties of the grouting were investigated. FT-IR analysis confirms the formation of carbamate grafted structure within graftedPU/EP IPNs via a reaction between-NCO of polyurethane and-OH of epoxyresin. TG analysis shows that grafted PU/EP IPNs grouting obviously exhibits abetter thermal stability than pure EP grouting below300℃, and its heatresistance is close to the latter at temperature higher than300℃; grafted PU/EPIPNs grouting presents optimal mechanical properties when R=2.5/1andPU/EP mass ratio is15/85. Impact fracture’s SEM images of grafted PU/EPIPNs grouting shows a transition from brittle frature to ductile fracture withincrease of PU-prepolymer’s content.Influences of various mass ratio and total amount of T31/low molecularweight polyamide650#, different amount of furfural-acetone diluent andvarious contents of promoter DMP-30on mechanical and working performancesof grafted PU/EP IPNs grouting were studied to get optimized formulation ofgrafted PU/EP IPNs grouting. The results indicate that grafted PU/EP IPNsgrouting with40wt.%of the furfural/acetone (mass ratio1:1) diluent,50wt.%of the T31/low molecular weight polyamide650#(mass ratio1:1) compositecuring agent,0.5~3wt.%of promoter DMP-30shows optimal performances, and the grafted PU/EP IPNs grouting with best formulation exbits60mPa·s ofinitial viscosity,1.5h of operating time,5.9MPa of dry adhesive strength,3.6MPa of wet adhesive strength,61.8MPa of compressive strength and25.5MPaof tensile strength. |
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