The Research Of Nano-TiO₂/Fluorinated Polyurethane Coatings With Low Surface Energy

In recent years, the low surface energy coating's potential application field expands unceasingly due to its own characteristics. For instance, it may be used in aerospace, marine industry, environmental self-cleaning application, printing, leather and textile, building materials, biological chemistry, metal smelting and other fields. Although many academic research results are present currently, low surface energy coating's performance cannot meet practical requirements. Therefore, this article aims at preparing a kind of polyurethane coating with excellent low surface energy and hydrophobicity. The work mainly includes two aspects.First of all, macromolecule polyurethane emulsifier was synthesized using hydroxyl ethyl methacrylate (HEMA) as end-capping agent. Then an A-B-A type tri-block fluorinated acrylate modified polyurethane emulsion (FPUA) was synthesized by radical free emulsion copolymerization of Dodecafluoroheptyl methacrylate (DFMA), Styrene (St), n-Butylacrylate (BA) and the macro-emulsifier. The structure of FPUA was confirmed by infrared spectra (IR) characterization. The effect of DFMA content on properties of coating, such as water absorption, surface properties, mechanical properties, corrosion resistance and thermal stability, were discussed. The results showed that when DFMA content was up to 15%, surface free energy was greatly reduced, and down to 15.1 mJ/m2. Meanwhile, the film had good mechanical properties. Its pencil hardness was increased to 4H. And its adhesion, flexibility and impact strength were kept at grade one,0.5mm and 50 kg · cm, respectively.Secondly, based on the inspiration of lotus leaf effect, nanoparticles filling method is used to construct the coating surface microstructure, in order to improve the hydrophobic property of coating. Surface modification of nano-TiO2 was done with silane coupling agent KH-171. Utilizing hybrid nano-TiO2 of two particle sizes, we prepared nano-TiO2/FPUA coatings which had low surface energy and hydrophobicity. The results showed that when the nano-TiO2 dosage was 12%, and proportion of nano-TiO2 with two particle sizes (mP25:mTA-60) was 3: 7, the coatings achieved better hydrophobicity and oleophobicity. Their contact angles were 130 °and 97.5°, respectively. Surface energy could be 5.53 mJ / m2 at this time.