Study On The Preparation And Film Forming Properties Of Modified Nano Silica/Fluorinated Waterborne Polyurethane-Polyacrylate Dispersions

With the development of environmental protection and safety, the performance demand of coating and paint products was becoming higher and higher. As the development of waterborne polyurethane(PU) industry, The scientists are focus on solving the disadvantages of PU hydrophobic enough, poor flexibility and insufficient tensile strength.In this paper, silane coupling agent(KH570) produced silicon alcohols by hydrolysising in acidic conditions and hydroxyl on the surface of nano-silica occurredpolymerization to realize the modification of nano silicon dioxide, then taking vinyl monomers place organic solvent by situ emulsion polymerization, the isophorone isocyanate(IPDI), poly(caprolactone) diol(PCL1000) and hydroxyl ethyl acrylate (HEA) was added to the system, forming the double bond-end PU pre polymer; Fluorine alcohol (FA) monomer containing carbon-carbon double bond and nano-silica was innovative introduced in polyurethane preformed stage. The initiator KPS initiated vinyl monomer occurred free radical polymerization. Finally, the modified nano silica/fluorinated waterborne polyurethane polyacrylate (WSFPUA) composite emulsion was synthesized. The effects of reaction conditions and the properties of KH-570 modified nano silica was studied in this paper, then the impact on the content of fluorine ester and nano-silica of WSFPUA composite emulsion and latex film morphology properties was studied. This paper main content is as follows:(1) In the experiment of modified nano-silica, the influence of different pH value, temperature and KH-570 content on the nano-silica stability and particle size was studied. The FT-IR and Morphology analysis results showed that the modifier KH-570 and the surface of nano-silica was combined by chemical bond. The stability of modified nano-silica was best and the smallest particle size reached to 78nm when the reaction temperature was 60℃。(2) In the nano-silicon/fluorinated polyurethane-polyacrylate (WSFPUA) hybrid emulsion, a series of different R value WSFPUA hybrid emulsion was prepared, the emulsion appearance and mechanical stability reached the best when R=1.05. The FT-IR results showed that nano-silica and fluorinated monomer was sucessfully introduced to polyurethane-polyacrylate emulsion. The transmission electron microscopy results showed that the emulsion particles WSFPUA were spherical and particles size were homogeneous.(3) A series of different nano-silica content WSFPUA was prepared, and the influence of nano-silica content on the WSFPUA emulsion, film appearance and performance was studied. The results showed that the appearance of emulsion gradually changed from a semi transparent to opaque white as the increasing of nano-silica content, meanwhile the mechanical stability decreased and particle size increased when the nano-silica content in the range of 0%-5%. The tensile strength of WSFPUA composite latex film increased from 43.08 MPa and the contact angle increased to 122.5。, but the water absorption decreased to 8.5%. Meanwhile the WFSPUA composite latex film surface smoothness and heat resistance increased significantly with the increase of nano silica.(4) The proprity of WSFPUA composite emulsion and latex film with different HEA content was studied, and then the impact on the latex film surface morphology, thermal stability, water resistance, tensile properties, SEM and coating properties were discussed. The WSFPUS latex film were getting more and more smooth, and the WSFPUA thermal stability, water resistance and tensile properties were improved obviously with the increase of HEA content.