Synthesis And Properties Of Room Temperature Multi-curing Waterborne Polyurethane Emulsion

Waterborne polyurethane has been widely studied and applied due to its unique properties.However,due to its inherent defects,a single waterborne polyurethane has disadvantages such as slow drying speed and poor water resistance,which limits its application and promotion.In order to improve its performance and expand its application,waterborne polyurethane coatings were prepared by room temperature multiple curing.The specific research contents are as follows:?1?2,4-toluene diisocyanate?TDI-100?,oligomer diol as the main raw material,dimethylolpropionic acid?DMPA?as hydrophilic chain extender,4,4'-dihydroxybenzophenone?DHBP?and linoleic acid glyceride were functional monomers,and triethylamine?TEA?was a neutralizing agent.The aqueous polyurethane hydroxy component containing a carbon-carbon double bond and a ketone carbonyl group in the molecular chain was synthesized by the acetone method.The effects of synthesis process and raw material ratio on the performance of aqueous polyurethane hydroxyl component and its cured film were discussed.The experimental results showed that when the prepolymerization temperature was 75?80°C,the prepolymerization time was 3.5?4h,the solid content was 35%,the neutralization degree was 100%;the oligomer diol was PTMG1000;the DMPA dosage was 6%;DHBP dosage was 5%;when linoleic acid glyceride was 20%,the aqueous polyurethane hydroxyl component and its coating film performance were better.FT-IR analysis indicated that the target product was synthesized.?2?The aqueous solution of the adipic acid dihydrazide?ADH?and the aqueous polyurethane curing agent were used as the crosslinking agent and the aqueous polyurethane hydroxy component synthesized under the optimal conditions of the previous step was physically blended to prepare the room temperature multiple curing water.Polyurethane coating.The effects of the addition of ADH and waterborne polyurethane curing agent and the curing time on the properties of waterborne polyurethane coatings were investigated.The TEM,FT-IR,TG and electrochemical analysis methods were used to analyze and characterize the waterborne polyurethane coating before and after modification.The results showed that when the alcohol ester 12was a filming aid;n?DHBP?:n?ADH?was 1:0.6;when the amount of waterborne polyurethane curing agent was 5%,the performance of the room temperature multi-curing waterborne polyurethane coating was the best.Of TEM analysis showed that theoretically multiple curing at room temperature can be achieved with a construction period of at least 2h.FT-IR analysis showed that the coating film achieved multiple curing at room temperature,and TG analysis showed that the room temperature multi-curing waterborne polyurethane coating had the best heat resistance.Electrochemical analysis showed that room temperature multi-curing waterborne polyurethane coatings have the best corrosion resistance.?3?The curing kinetics of room temperature multi-curing waterborne polyurethane coatings at different heating rates were studied by non-isothermal DSC method.The kinetic parameters of different curing methods were calculated by Kissinger equation,Ozawa equation and Grane equation.The apparent activation energies Ea of the single-curing,double-cure,and multiple-cure corresponding coatings were 100.02 k J/mol,89k J/mol and 77.73k J/mol;the reaction orders n were 0.927,0.922,0.915,The frequency factors A were 14980.68s^-1,9690.04s^-1 and 1040.09s^-1.The activation energy of the reaction at different degrees of cure was calculated using the Flynn-Wall-Ozawa method.