| The polyurethane waterproof coating after curing has excellent elasticity,abrasion resistance,corrosion resistance,etc.,and has been widely recognized and applied in the field of building waterproofing.However,with the continuous development of our country's railway construction and the extension of the total distance of high-speed railways,the waterproofing of railway road and bridge engineering puts forward higher requirements for polyurethane waterproof coatings.At the same time,polyurethane waterproof coatings turn to become more and more environmental-friendly and easier for construction.In this paper,the more environmentally friendly diphenylmethane diisocyanate(MDI)is used to partially replace toluene diisocyanate(TDI)to prepare a high-strength two-component polyurethane waterproof coating that can meet the waterproof requirements of the railway road and bridge engineering field.At the same time,it is more convenient for construction.Latent curing single-component polyurethane waterproof coating has been studied,too.In this paper,a more environmentally friendly high-strength two-component polyurethane waterproof coating was prepared by using MDI and TDI.The kinetics of polyurethane prepolymerization was studied by chemical analysis,and the isocyanate monomers,feeding methods,and isocyanate index(R value)were discussed.The influence of the ratio of polyether glycol and triol,the amount of talc,and the type and amount of defoamer on the performance of waterproof coatings are also studied.The kinetics study of pre-polymerization reaction shows that the polymerization rate rises continuously as the temperature increases,and the activation energy of the reaction(Ea)is 204.748 k J/mol.As the dosage of MDI increasing,the tensile strength and elongation at break of the coating film both descend,but thermal stability improve.With the increase of the R value in the A component,the tensile strength of the coating film ascends,and the elongation at break decreases little by little.When the R value is 3.5,the coating film has good mechanical properties,and its tensile strength reaches 5.15 MPa,also the elongation rate reaches 432%;when the molar ratio of diol:triol is 2:1and the amount of talc powder is 45% by mass,the coating film shows good mechanical properties;non-silicone consumption foaming agent(BYK-054,DF831)has better defoaming effect,and the coating film shows more excellent mechanical properties.The performance indicators of the waterproof coating film prepared on the basis of the optimized experimental formula basically meet the relevant standard requirements of the "Polyurethane Waterproof Coatings"(GB/T 19250-2013)standard for the non-passable parts of railway bridges.In this paper,a latent-curing single-component polyurethane waterproof coatings was prepared used TDI as the monomer,and with imine-type and oxazolidine-type latent curing agents and environmentally friendly solvents.The latent curing mechanism of the coating film was analyzed,and the polyether triol was studied.The influence exerted by dosage of triol,R value,type and dosage of latent curing agent on the performance of waterproof coating were also studied.The results show that as the R value increasing,the tensile strength of the coating film increase;as the amount of polyether triol increasing,the tensile strength of the coating film increases steadily,and the optimal mass ratio of polyether diol and triol is 3:7.The coating at this mass ratio has higher tensile strength and elongation at break;the coating film prepared with imine-type latent curing agent is denser and has fewer surface pinholes,and the amount of 1%?1.5% can get better comprehensive performance. |
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