The Preparation Of Aqueous Polyurethane Dispersions And The Research Of Secondary Chain Extension

Nowadays, society is still facing serious environmental problems such as environmental pollution and energy shortage, which causes the irreconcilable contradiction between environmental problems and economic development. With the development of society and attention on environmental issues, governments have introduced appropriate laws and regulations to restrict the production of environmental pollution. Aqueous polyurethane material, a kind of water-dispersible polymer which mainly dispersing medium is water, little or no organic solvents, which can meet the current environmental requirements on polymer materials. As the replacement of solvent-based polyurethane materials, Aqueous polyurethane material possess characteristics such as green, safe and reliable, clean and excellent mechanical properties, which widely used in construction, furniture, printing and other aspects closely related to our daily life.The material has good physical and mechanical properties, excellent weather resistance, low temperature resistance, abrasion resistance, etc, and its "tailoring" structure which can design polyurethane materials with different structures. Currently, there is a wide variety of aqueous polyurethane products on the market that can meet the requirements of industries, but for the theory of aqueous polyurethane chain processing is relatively empty. Our group did some theoretical research about after chain processing of aqueous polyurethane dispersion, using the method of ninhydrin coloring terminal amino resin. This paper is divided into three parts:(1) The preparation and performance testing on aqueous polyurethane dispersionsNinhydrin can only color primary amino which directly connected with sub-methylene (-CH2). For ensuring the synthetical aqueous polyurethane dispersion can meet the testing condition, we choose isocyanate HDI and polyether diol as the main raw material and adopt prepolymer method to synthesize aqueous polyurethane dispersion, while ensuring -NCO excess before emulsification, after chain extension by adding the right amount of water and ethylene diamine the base resin of end group is the primary amino group connected directly with times methylene. Fourier transform infrared spectrum(FT-IR) shows that the synthetic end group of resin is primary amine; Particle testing show the diameter of the resin is small and narrow, synthetic resin dispersions is stable with the test of mechanical stability; UV determined the optimal concentration of resin.(2) Research on secondary chain process of aqueous polyurethane by different isocyanatesThis chapter researched the process and performance of secondary chain on aqueous polyurethane by three common diisocyanate (HDI,MDI,TMXDI). Fourier transform infrared spectrum(FT-IR) shows that added HDI in process of secondary chain is completely reacted, Ureido peak slightly increased, amino been enhanced. UV shows that content of resin side amino increased after secondary chain by HDI and IPDI, but for TMXDI reduced. Tensile testing indicates that secondary chain made tensile strength of film greatly improved, elongation at break increased at certain extent, as the modulus, which descript that secondary chain took place chain extension reaction instead of crosslinking. We can obtain the optimum amount of secondary chain extender combining with tensile strength and its standard curves. Particle testing shows that dispersion of particle is essentially same after second chain, so secondary chain does not affect the stability of emulsion. TG shows that the thermodynamic properties of the secondary chain extender makes only a slight increase in film, for the secondary chain extender is diisocyanate, which not available good heat resistance. Resistance rates basically unchanged toluene, water absorption decreased slightly, indicating that the secondary process chain for chain reaction, do not form a crosslinked structure.(3) Research on different epoxy resin aqueous polyurethane secondary process chainThis chapter compared three free hydroxyl structure of three epoxy (epoxy resin of 1,4-butanediol, ethylene glycol epoxy resin, epoxy resin polyethylene glycol) chain extension of the aqueous polyurethane secondary process impact. Infrared tests showed join the ring-opening of epoxy groups and terminal amino resin reacts the secondary hydroxyl groups and secondary amino groups; UV test adding three kinds epoxy resin terminal amino group content were decreased, indicating that the secondary chain extension process of ring-opening of epoxy groups and the terminal amino group of the resin chain extension reaction occurs; secondary particle diameter after the test showed that the dispersion particle diameter of the chain extender increases slightly lesser extent, it will not increase the size of a stable emulsion sex have an impact; corrosion rate basically unchanged toluene, water rate declined slightly, indicating the occurrence of a chain process chain reaction rather than crosslinking.