Study On The Synthesis Of TDI Modified Epoxy Prepolymer Active Hydrogen Curing Agents And Coating Properties

Bisphenol A type epoxy resin is cheap and has good adhesion, mechanicalproperties and corrosion resistance. So it widely used in coatings, construction,adhesives and other industries. The same time, coal tar as a byproduct of coking, hasexcellent properties like aging resistance, waterproof, antiseptic and anti-microbialerosion to make it used for severe anti-corrosion. This paper based on the characteristicthat isocyanate groups easy to react with hydroxyl, uses TDI and epoxy as raw materialsynthesized a new curing agent which can cure macromolecules with active hydrogengroups. By experiments determined the formula and process of preparing the curingagent. After removing water, coal tar as a film-forming material to prepare mainanti-corrosion paint by adding solid fillers and additives. Then using homemade curingagent and coal tar main paint to confect anti-corrosion coatings, determined the coatingformulations, studied coating combination property.The optimization formulation and process of synthesis the curing agent are asfollows: R value (the molar ratio of TDI and epoxy-OH)1.5,1.2%of the antioxidants,the reaction insulation90°C, the reaction time is5h. Finally the performance of thecuring agent is better, viscosity and-NCO content are respectively28.2mPa s and3.06%. The infrared spectroscopy characterization indicates that the reactants epoxyhydroxy peaks disappeared,-NCO characteristic peak intensity decreases, products haveurethane groups. This shows that TDI successfully modified epoxy resin, andsynthesized terminal-NCO prepolymer, but epoxy group had no change. TG/DTA testsshow that the thermal stability of modified prepolymer is better than the epoxy resin.MS software simulate the reaction of TDI and epoxy resin, calculate the activationenergy of different molecular weight epoxy resin (n=1,2) hydroxyl react with differentpositions-NCO of TDI. From the results know, the epoxy resin of low molecular weight(n=1) due to steric effects of the response required activation energy is2times for n=2;4-NCO of2,4-TDI is easy react with-OH than the2-NCO, the latter reactionrequires activation energy is the former two times.Homemade curing agent and coal tar main paint prepared coatings, by experimentsdetermined the best quality ratio is1:1. The film is good, and its surface is highlyreflective like mirror. The mechanical properties of the coatings are better especially theoutstanding flexibility, and hydrophobic angles all about80°. Tafel and the pointcorrosion test of chemical solution on the films, shows that the corrosion resistance ofthe film is better. In order to improve the compatibility in two-phase and the filmcross-linking, adding cyclohexanone and different amounts of hydroxyl resin to the coaltar paint. Through the test to know that the coating has good corrosion resistance whenadding the amount of cyclohexanone is10%and acrylic resin is20%. The corrosion voltage is-0.48V.