Investigating the Process of Surface Degradation and Nanoparticle Release of a Commercial Nanosilica / Polyurethane Coating Under UV Exposure | NIST
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A series of polydodecylmethylsilsesquioxane (PDMSQ) nanocomposite latexes were prepared via emulsion polymerization of methyltriethoxysilane (MTES) and dodecyltrimethoxysilane (DTMS) and sodium hydroxide as the catalyst, and sodium dodecyl benzene sulfonate/Tween 80 as the mixed emulsifiers. Effects of the emulsifier doses, the reaction temperature, the catalyst concentration and the oil/water ratio on the particle size and distribution of the PDMSQ nanoparticles were discussed. Particle size and micromorphology, structure, thermal stability, crystallinity and hydrophobicity of PDMSQ nanoparticles (PDMSQ NPs) were investigated by dynamic laser scattering (DLS), Fourier transform infrared spectroscopy (FTIR), silicon-nuclear magnetic resonance (28Si-NMR), X-ray photoelectron spectroscope (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), thermo gravimetric analysis (TGA), X-ray diffraction (XRD) and contact angle tester. Results showed that a series of PDMSQ NPs could be obtained with an average particle size of less than 80 nm and narrow distribution as well as spherical structure under the optimal process conditions. PDMSQ NPs exhibited excellent thermal stability and were mainly amorphous but also contained some crystal structures. Importantly, the static water contact angles (WCAs) on its latex films were larger than 150° and the WCAs hysteresis were less than 10°, thus those PDMSQ nanocomposite latexes show potential in the field of superhydrophobic coatings.
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Novel, environmentally friendly waterborne coatings were obtained from the filmification of nanostructured latex particles reinforced with inorganic nanotubes. The latex used to form the coatings consists of core-shell particles with a shell functionalized with different amounts of acrylic acid (AA). This external polymer layer was doped, in some cases, with TiO2 nanotubes at three different concentrations: 100, 500 and 1000 ppm. The composite particles were synthesized in two steps by semi-continuous emulsion polymerization at 75°C. A series of films was prepared by employing core-shell particles with different sizes, core cross-linking and shell functionalization. The coatings obtained were characterized by infrared spectroscopy (FTIR), tapping mode atomic force microscopy (TM-AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetrical analysis (TGA). Drying rates and tests were also performed to further evaluate these films. It was observed that the addition of small amounts of TiO2 nanotubes contributes to improve the application properties, mainly adhesion to metallic substrates and water impermeability. The resistance to thermal degradation was also strongly increased, as showed by the DSC and TGA analyses.
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Rutile titanium dioxide (TiO 2 )/poly(methyl methacrylate‐acrylic acid‐butyl acrylate) nanocomposites were synthesized via seeded emulsion polymerization and characterized by Fourier transmission infrared, dynamic light scattering, X‐ray diffraction, ultraviolet–visible (UV–vis) spectroscopy, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis to study their UV‐shielding property. The effects of the nanoseed types, surfactant concentrations, and functional monomer amounts on the polymerization conversion, particle size, emulsion stability, and morphologies of the resulting nanocomposites were investigated. The dependence of UV‐shielding performance on the nanoparticle content and dispersion was also explored. The optimized results are obtained with 2 wt% of TiO 2 nanoparticles addition, and the effectiveness of UV shielding is significantly increased by using the synthesized rutile nano‐TiO 2 /polyacrylates, for which the nanocomposite coating with a thickness of 200 μm could block up to 99.99% of UV light (≤350 nm) as confirmed by UV–vis spectrometry. POLYM. COMPOS., 36:8–16, 2015. © 2014 Society of Plastics Engineers
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The target of this work is to choose a suitable nanoparticle for preparing a highly ultraviolet (UV)-shielding from poly (methylmethacrylate)(PMMA) nanocomposites at low concentration and to decrease the destructive effects of UV radiation. Morphologies of the synthesized nanoparticles were investigated by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM). Whereas, pure PMMA and its nanocomposites were characterized by using dynamic mechanical analysis (DMA), tensile testing, UV-visible spectra (T%), and thermogravimetric analysis (TGA). The obtained results showed a good correlation between the tensile properties, DMA and TG analysis depending on the type of nanoparticles used in the PMMA matrix, especially in case of ZrO2 and ZnO. Furthermore, UV-vis spectra were analyzed ranging from 200 nm to 800 nm. It showed that UV radiation is significantly blocked from 100% to 0.2 % in the UV range between 200 nm and 360 nm for pure PMMA and to 0.08 % for PMMA/CeO2 nanocomposite and to 0.01 % for PMMA/CeO2 with various types of nanoparticles. After 360 nm, pure PMMA and PMMA/CeO2 were a little bit affected by UV lights, whereas the PMMA based on different nanoparticles was not affected. This result demonstrates that these nanocomposites could be strongly candidates for the sunscreens or for several fields that related to the UV photodegradation effects.
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The object of this paper is to study the effect of silica nanoparticles (SiO2 NPs) on waterborne polyurethane films (5×10-3 to 5wt % SiO2 NPs). The Nanocompounds’ properties were analyzed by thermogravimetric analyzer (TGA), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and dynamic mechanical analyzer (DMA). From the results, the nanocomposites degraded at a higher temperature than pure PU matrix. Moreover, the temperature where the weight loss reached 50% was shifted by 57oC towards higher temperature when the silica nanoparticle content was 5 wt%. The crystallinity, mechanical strength as well as thermostability the PU were influenced by the concentration of silica nanoparticles.
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Abstract Atomic force microscopy has been applied for measuring the nanomechanical characteristics of poly(methyl methacrylate) thin films containing 5% photoinitiator (Irgacure 651). The nanohardness, Young's modulus, and adhesion to AFM tip have been evaluated for the unexposed samples and after UV‐irradiation. Additionally, FTIR spectroscopy and differential scanning calorimetry (DSC) have been applied to explain the observed changes in nanomechanical properties. It was found that the exposure to ultraviolet changed the nanomechanical properties of polymer because of photo‐oxidative degradation and relaxation processes. These studies lead to the conclusion that the applied photoinitiator has no noticeable effect on nanohardness and Young modulus during PMMA irradiation, but efficiently participates in polymer photo‐oxidation increasing the surface hydrophilicity and adhesion to Si 3 N 4 . Moreover, the initiator hampers the relaxation of PMMA macromolecules, what was proved by DSC. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
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