| Waterbome Polyurethane(WPU) which is dispersed by water is one of environmentally friendly green materials. It has been widely used in lot of fields because of its advantages of low content of volatile organic compounds and the characteristics of energy saving. However, the single WPU emulsion also has some disadvantages which make it can’t satisfy the demands of performance in different fields, such as the poor mechanical properties, the lower hardness and the bad water resistance of film. So the WPU should be modified. It is need to find a kind of renewable, biodegradable, inexpensive substance to modified WPU because of the problem of environmental pollution and energy shortage. Castor oil (CO) can be epoxidized and obtain the epoxidized castor oil (ECO) due to the double bond, hydroxyl group, ester group in CO. WPU modified with ECO can achieve the effect of waterborne polyurethane modified with epoxy resin, which is the direction of research of innovative green.In this study, the single factor test was used firstly, epoxy castor oil was synthesized with the material of castor oil (CO), acetic acid (CH3COOH), hydrogen peroxide (H2O2), activated alumina. The influence of types of carboxylic acids, reaction time, reaction temperature, dropping temperature of H2O2 and amount on the epoxy reactions were explored, and according to the results the optimal conditions for epoxy castor oil were gotten:n (CO double bond):n (CH3COOH):n (H2O2)= 1:1.3:2.5, mass of acidic alumina for 10%CO, the quality of urea for 0.3%CO, dropping temperature of H2O2 was 55 ℃. the reaction should be kept for another 12.5 h at 65℃ after completion of dropping of H2O2. The crude product was washed and dehydrated to obtain the epoxy castor oil which epoxy value up to 3.12%. The products were characterized mainly by infrared spectroscopy (FT-IR) and the test of acetone and hydrochloric acid.WPU was modified with the above-prepared ECO. Emulsions and films were prepared by diphenyl methane diisocyanate (MDI) which has the lower toxicity, polyethylene glycol 600 (PEG600),2,2-dimethylol propionic acid (DMPA),1,4-butanediol (BDO), triethylamine (TEA),etc, and to explore the influence of the reaction conditions and the amount of reactants in the preparation process. Experimental results show:prepolymerization for about 2.5 h in 75-80 ℃, then chain extension reaction at 65-70℃, at last neutralization and emulsification at room temperature, and it was found that when wECO= 5.5%, the resulting emulsion and film had the best performance. The effects of modification on the structure and properties of waterborne polyurethane were characterized by using fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG), transmission electron microscopy (TEM), contact angle measurement, mechanical testing methods.Meanwhile, the study also prepared polyurethane modified by bisphenol A type epoxy resin (E-44), and discussed the differences of the performance with waterborne polyurethane modified by ECO. On the one hand, waterborne polyurethane modified by ECO has superior performance in the hydrophobicity when compared to waterborne polyurethane modified by E-44, on another hand other properties of two kinds of modified WPU were almost the same. |
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