| Aqueous Polyurethanes(PU) were used widely in coating, adhesive, weave finishing and so forth in recent years due to their excellent softness, stiffness, adhesive, elasticity and other properties. Urethanes are known to deliver chemical, water and especially abrasion resistance. They can also be designed to have high tensile and impact strength, along with excellent low temperature flexibility. Due primarily to environmental reasons, water-borne urethanes have grown commercially over the last thirty years. Compared to their solvent counterpart, aqueous urethane dispersions can offer the following advantages: viscosity and flow properties independent of molecular weight, the absence of external emulsifiers, environmental safety, good adhesion and rheology characteristics. However aqueous urethanes are deficient in chemical resistance compared to cross-linked two-pack solvent based urethanes. This is because most water-borne urethanes are linear thermoplastic polymers with very little gel content that allows resolubility in solvent. High levels of pre-cross-linking cannot easily be introduced into water-borne urethane due to problems of high viscosity prepolymers or poor coalescence of the formulated dispersins. Aqueous urethanes with a limited number of cross-link sites are known and do show improvements, but not to the same degree as two-pack solvent systems. To overcome these problems, many works had been developed a variety of room temperature curable cross-linkers were designed to improve the performance aqueous urethanes and acrylic latexes. This paper will give three kinds of self-cross-linkable water-borne polyurethanes.First, we synthesized polyurethane prepolymer contain carbonyl-functional group in it s backbone using dihydroxyacetone as chain extender;secondly, weused3-[bis(2-hydroxyethyl)amino]-N-(1,1-dimethyl-3-oxobutyl)prop anamide as a chain extender to get a perfect effective single-package self-crosslinkable waterborne polyurethane with carbonyl-functional group,cross-linking reaction were observed even at ambient temperature.Thirdly, a hydroxyl-terminal acrylic acid macromonomer was synthesized by radical copolymerization of acrylate and diacetone acrylamide (DAAM) with mercaptoethanol as chain-transfer agent, cross-linkable aqueous polyurethane dispersion was obtained by reacted the macromonomer with NCO-terminal prepolymer with build in hydrophilic groups. At the same time, adipic acid dihydrazide was poured into the dispersion to couple the polymer molecular.The aqueous polyurethane dispersion we obtained display marvelous storable stabilities without losing cross-linking reactivity. The relationship that rate of translation and time of reaction of diacetone acrylamide and diethylamine was determined by UV. We studied how content of crosslinkable groups and content of hydrazide influence article size and stability of the dispersion, and studies also emphasized on the influence of elongation at break, tensile strength, hardness, water-proof of PUD films, and we proposed the group site may influence properties of PUD films. Characterize the cross-linking between the keto group and the hydrazine group by FT-ATR. The hard-soft segmental structure, phase separatio of the film were tested by diferential scanning ealorimetry(DSC),thermogravimetry analysis(TG), dynamic mechanical analysis(DMA). The mechanical and chemical resistance properties of the polyurethane films at different crosslink densities are compared along with the effect of self-condensation of the various crosslinker. Study indicated the film made from the title dispersion have good waterproof, high resistance to oil or solvent and excellent mechanical properties.
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