angxin Gu

A facile and large-area fabrication method of superhydrophobic self-cleaning fluorinated polysiloxane/TiO2 nanocomposite coatings with long-term durability

A long-term superhydrophobic self-cleaning coating was first fabricated by simply blending ambient-cured fluorinated polysiloxane binder with TiO2 nanoparticles. The obtained coating has excellent durability in various environments, and this method can be used for large-scale fabrication of self-cleaning coatings for practical applications.

Study on the morphology and tribological properties of acrylic based polyurethane/fumed silica composite coatings

Two fumed silica (one hydrophilic and one hydrophobic) were used in the high solid acrylic based polyurethane coatings by directly mixing. The dispersion of fumed silica particles in the bulk of polyurethane coats was characterized by transmission electron microscope (TEM) and surface morphology examined using a scanning probe microscope (SPM). Micro indentation and scratching tests were carried out with a nano-indenter. Both hydrophilic and hydrophobic fumed silica nearly have the same dispersion in acrylic based polyurethane coats. The surface roughness of polyurethane coats increases as fumed silica increases, however, the surfaces of polyurethane coatings containing hydrophobic fumed silica are rougher than that containing hydrophilic fumed silica at the same content. Addition of fumed silica can obviously enhance the micro indentation hardness (MIH) and elastic modulus of polyurethane coats and the higher the content of fumed silica is, the higher the MIH is for hydrophilic one but for hydrophobic one only under normal load less than 20 mN. In the micro scratch experiment, the elastic response and plastic deformation nearly keep constant with normal force increasing for pure acrylic based polyurethane coats. But the percentage of elastic response decreases and the percentage of plastic deformation increases as normal force increases for the polyurethane coats with fumed silica. Crack occurs when scratching under normal force higher than 50 mN for the polyurethane coats with fumed silica, and as the content of fumed silica increases, the critical force for crack increases. Additionally, both hydrophilic and hydrophobic fumed silica have no obvious influence on the response to marring stress and micro mar resistance (MMR) of acrylic based polyurethane.

Synthesis and antibacterial property of hollow SiO2/Ag nanocomposite spheres.

This paper presents a novel and facile method to fabricate hollow silica/sliver (SiO(2)/Ag) nanocomposite spheres. In this approach, the monodisperse hollow SiO(2) colloids bearing quantenary ammonium groups were prepared by dispersion polymerization combined sol-gel process and used as templates. The Ag(+) ions were first adsorbed onto the surfaces of the hollow SiO(2) beads via electrostatic interaction and then in situ reduced by the deprotonated silanol groups of the hollow SiO(2) beads, no extra reducing agents or catalysts were added during the reduction process. TEM, SEM and EDX analyses indicated that Ag nanoparticles were successfully deposited onto the surfaces of hollow SiO(2) beads. Some influencing parameters, such as the amount of quantenary ammonium groups in the inner wall of hollow SiO(2) colloids, Ag(+) ions concentration and reaction temperature, on the deposition of Ag nanoparticles onto SiO(2) colloids were investigated. Preliminary antibacterial tests indicated that these hollow nanocomposite spheres showed excellent antibacterial ability.

Modification and dispersion of nanosilica

Abstract The modification and dispersion of nanosilica particles were investigated by Fourier transform infrared spectroscopy (FTIR), 29Si CP MAS NMR, thermal gravimetric analysis (TGA), Raman spectroscopy, particle size analysis, transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA) using methacryloxypropyltrimethoxysilane (MAPTS) as the modification agent. It was found that MAPTS grafted onto silica particles, and exists in a T2 structure. TGA data show that the nano‐silica particles with higher specific surface area and hydroxyl content could be grafted with more MAPTS than those with lower specific surface area and hydroxyl content. Increasing temperature was more significant than extended reaction time for increasing modification effects. MAPTS modification was beneficial for decreasing the particle size of nanosilica, and for improving their dispersion in resin.

Wettability switching of SDS-doped polyaniline from hydrophobic to hydrophilic induced by alkaline/reduction reactions

In this paper, sodium dodecyl sulfate (SDS) is used as dopant to manipulate both morphology and wettability of polyaniline (PANI). When SDS amount is controlled within a certain range, micro/nano double-rough PANI with hydrophobic surface can be obtained, while insufficient or excess SDS can only lead to hydrophilic PANI. The double-rough PANI shows stimuli-responsive change in wettability to either alkaline reaction or reduction reaction from hydrophobicity to hydrophilicity. This quick response can be applied to quantitatively estimate NaOH concentrations within the range of 10(-3)-10(-1)M and to detect various reducing liquids.

Preparation and Characterization of Acrylic/Nano-TiO2 Composite Latex:

Acrylic/nano-TiO2 composite latex samples were prepared via high-shear stirring and mixing (SM), ball milling and mixing (BM) and in situ polymerization (IS) methods, and investigated by transmission electron micrography (TEM), testing with an Instron machine, dynamic mechanical analysis (DMA) and ultraviolet-visible (UV-VIS) spectrophotometry. It was shown that the IS method led to the best dispersion of nano-TiO2 particles in acrylic copolymer films, the SM method was the second best and the BM method gave the least good result. Addition of nano-TiO2 by SM and BM methods led to higher tensile strength and Tg for polymers than introduction with micro-TiO2 and without any fillers. UV-VIS spectra indicated that addition of nano-TiO2 into acrylic copolymers could increase the absorbance and decrease the transmittance in the UV region, whereas the absorbance or transmittance in the UV region basically remained unchanged for the composites filled with micro-TiO2.

Study on Modification and Dispersion of Nano‐silica

The modification and dispersion of nano‐silica particles were investigated by Fourier transform infrared spectroscopy (FTIR), 29Si CP MAS NMR, thermogravimetric analysis (TGA), Raman spectroscopy, N4Plus particle size analyzer, transmission electron microscopy (TEM), and dynamic mechanical analyzer (DMA) using methacryloxypropyltrimethoxysilane (MAPTS) as the modification agent. It was found that MAPTS had grafted onto silica particles and existed in T2 structure. TGA data showed that the nano‐silica particles with higher specific surface area and hydroxyl content could be grafted with more MAPTS than those with low specific surface area and hydroxyl content. Increasing temperature has more impact than extending time for increasing modification effect. MAPTS modification was beneficial for decreasing particle size of nano‐silica, improving its dispersion in resin.

Dependence of dirt resistance of steel topcoats on their surface characteristics

Contamination of exterior coatings with dirt is a significant problem in seriously polluted environments. To correlate the dirt resistance of exterior coatings with surface characteristics (wettability, roughness, and composition), steel topcoats were evaluated using both dirt pick-up tests according to a national standard testing method of China (GB/T 9757-2001) and outdoor exposure experiments in Shanghai, China. These topcoats included polyvinylidene fluoride (PVDF) paints with various water contact angles (WCAs), polyurethane (PU) paint, polysiloxane (PSiO) paint, and 2K fluorocarbon (FPU) paint. Opposite dirt resistance results were obtained from these two dirt pick-up methods. In the outdoor exposure experiments, superhydrophilic PVDF paints showed excellent self-cleaning performance and thus superior dirt resistance. Superhydrophobic PVDF paint exhibited self-cleaning performance initially, but became dirty finally due to a piling up of PM2.5 pollutants. PVDF paints with WCAs of 85°–125°, PU, PSiO, and FPU paints all exhibited poor dirt resistance in the outdoor environment. These results indicate that dirt resistance depends on surface wettability and the characteristics of pollutants rather than on the surface roughness and composition.

Long-term hydrophobicity and ice adhesion strength of latex paints containing silicone oil microcapsules

Waterborne anti-icing coatings were prepared by embedding silicone oil microcapsules in latex paints. The long-term hydrophobicity and ice adhesion strength of the coatings were examined with a QUV accelerated weathering tester and a pull-off adhesion tester. The effects of silicone oil content and pigment/binder (PB) ratio on the long-term hydrophobicity and the ice adhesion strength of the coatings were investigated. A higher silicone oil content and a PB ratio close to the critical pigment volume concentration favor long-term hydrophobicity of the coatings. An obvious decrease in ice adhesion strength was achieved for coatings with a PB ratio of 5.0 and a silicone oil content of 4.2%. For coatings with the same surface roughness, a higher water contact angle (WCA) led to lower ice adhesion strength. However, for coatings with different surface roughnesses, the ice adhesion strength was found to be dependent on surface roughness rather than on WCA.

Preparation and Characterization of Silicone-Grafted Styrene-Butyl Acrylate Latex Copolymer

Hydroxyl silicone oil was successfully grafted to the styrene(St)-butyl acrylate(BA) copolymer chain by reacting with functional monomer, γ-propylmethacrylate trimethoxysilicane (PMTS), using the traditional emulsion polymerization method. The surface and interface composition, hydrophobic property, water repellent property and glass transition temperature (T g) of the silicone-modified St-BA copolymer films were investigated by Fourier transform infrared spectrometer coupled with attenuated total reflectance (FTIR-ATR), optical contact angle measurement 15 (OCA-15), weight of water absorption method and differential scanning calorimeter (DSC). FTIR-ATR spectra show that the silicone-modified St-BA copolymer films are rich in silicone units or segments at their surfaces compared with those in bulk and at interface, and have good hydrophobic properties. High drying temperature can more effectively increase silicone concentration at the surface, contact angle and hydrophobic properties of polymer films than extending drying time. Introduction of hydroxyl silicone oil or γ-propylmethacrylate triethoxysilicane (PMTS) can increase the T g of copolymer.