Soft Segment Side Chains Into The Preparation Of Fpu And Its Structural Properties

Fluorinated polyurethane not only posseses a whole range of very interesting properties, such as excellent mechanical properties, resistance to low temperature and adhesive property that PU domains, but also has very low surface energy and outstanding thermal stability, weather resistance and chemical resistance. Therefore, it has wide-spread application and development potential in defense, industry and civil fields.Firstly, in this dissertation a fluorine-containing epoxy compound(FO) was synthesized via open, closed-loop two-step ways, with 2,2,3,3-Tetrafluoro-1-propanol (TFP) and epichlorohydrin (ECH) as the raw materials. The effect of catalysts, reaction temperature and reaction time on etherification products yield was investigated. The results showed that the structures and size of the catalysts had great influence on the ether production yields, as the electron withdrawing group can reduce the nucleophilicity of TFP, which led to a reduced productivity. Due to their easy affinity to substrate, the productivity was increased by the increasing size of the electron donating groups. Appropriately increasing ether etherification time and temperature was conductive to the improvement of the yield of ether, but too long time and too high temperature will lead to the formation of by-products. For the closed process, the case was similar, as further extension of time and temperature was found to aggravate the hydrolysis of etherification products and FO. The fluorinated glycol (FOL)with a very narrow molecular weight distribution was synthesized through cationic ring-opening polymerization. with tetrahydrofuran and the above mentioned FO as the reactants. The effect of the ratio of materials and reaction time on molecular weight was then studied. It was found that with an increasing volume ratio of THF/FO, the molecular weight of FOL decreased: initially, the molecular weight of FOL increased by the extension of reaction time, but when the reaction reached a certain extent, the molecular weight decreased. Finally, FPU was prepared with the fluorinated group attatched to its soft chains. X-ray photoelectron spectroscopy (XPS) was applied to research the surface fluorine content of FPU. It was also found that by adjusting the FPU chain structure, we can control the enrichment effect of fluorinated chains which may migrate to the FPU surface. Compared with PU which had the similar molecular weight, it was obvious that FPU showed a bettter thermal stability, alkali resistance and water repellence.