Studies On The Properties Of Polyurea With Novel Chain Extender And Blockers

The technology of polyurea is another remarkable technological progress after waterbornecoatings, powder coatings and metal coatings. Polyurea reacts faster than the polyurethane and havehigh mechanical strength. However, the react is so fast that the polyurea film often discontinuous andstratified. And most of the present polyurea technology is about solvent-basted or none solventelastomer, there is a few of the water based dispersion of polyurea. In this paper, we synthesized twokind of diamines as chain extender and the gel time was prolonged when the new chain extend wasused to synthesize polyureas, Introducted hydrophilic chain extender into polyurea, then through thefree-radical emulsion polymerization, polyurea-acrylate hybrid emulsion was synthesized by addinginitiator acrylate. The specific process was as follows:1. N-ethyl-3,6-diamino-carbazole as chain extender to synthesize polyurea.During the alkylation-nitration-reduction step, the carbazole was first treated in a alkylationprocess in dibromoethane, and followed by nitration in nitric acid, in the final step to prepareN-ethyl-3,6-diamino-carbazole,-NO2was reduced to-NH2by stannum particles in concentratedhydrochloric acid to reflux. then reaction with polyurea prepolymer. The results showed that the geltime prolonged, polyurea have improved waterproof performance, mechanical strength, and corrosionresistance. When the content of NCO from5%increase to25%, gel time from86s decrease to43s,water absorption from12.1%decrease to4.9%, tensile strength from12.3MPa increase to21.2MPa,elongation at break from532%decrease to260%, after soak in brine, tensile strength reduce by1.7%and elongation at break reduce by5.1%.2.2,5-di(4-aminophenyl)-1,3,4-oxadiazole as chain extender to synthesize polyurea.The2,5-di(4-aminophenyl)-1,3,4-oxadiazole was synthesized by p-aminobenzoic acid andhydrazine hydrate, then reaction with polyurea prepolymer. When the content of NCO from5%increase to25%, gel time from124s decrease to40s, water absorption from13.3%decrease to6.5%,tensile strength from11.2MPa increase to20.1MPa, elongation at break from590%decrease to280%,after soak in brine, tensile strength reduce by1.5%and elongation at break reduce by3%.2. acrylate-polyurea hybrid emulsion.The polyurea prepolymer was synthesized by2,4-Diisocyanatotoluene,D-2000and2,2-dimethylol propionic acid(DMPA), then enveloped with hydroxyl ethyl methyl acrylate. Thesystem was neutralized with emulsifier. Waterborne acrylate-polyurea was prepared by makingpolyurea polymerized with acrylate. The best technique conditions were obtained which is R0 within the range of4~4.5, Rtwas1.5, the dispersion have good stability. That the viscosity andwater absorption of film increased with the adding of the content of dimethylolpropionic(DMPA), Which was moderate when the content of DMPA was7%. When the contentof acrylate was30%, other was polyurea, the film have the best mechanical strength, tensilestrength was25.6MPa, elongation at break was462%, also, the film decompose from200℃to400℃. after soak in brine, mechanical strength reduce by2%.