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Recent Developments in Waterborne Polyurethanes for Coating Applications
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Verónica L. Mucci, Mirta I. Aranguren, Javier I. Amalvy, María E. V. Hormaiztegui
Silica hollow capsules were used to encapsulate a corrosion inhibitor, 2‐mercaptobenzothiazole, and were incorporated in a commercial WPU [39]. Although the addition of the capsules affected the coating barrier properties, it provided short-term protection against corrosion. Hollow silica microcapsules loaded with the same corrosion inhibitor and incorporated by blending were used by Mirmohseni et al. to improve the thermal and barrier properties of self-healing coatings. Their results showed that adding 1 wt.% of silica capsules enhanced the adhesion of the WPU to aluminum substrates, maintaining the improvement in barrier properties. Higher capsule concentration resulted in the coating being more prone to corrosion than the neat WPU [40]. On the other hand, Yuan et al. included a silicate obtained by sol–gel in a WPU, and the resulting coating with 4 wt.% of filler had higher mechanical properties, impermeability, and better bonding properties compared to the neat WPU [41]. Another family of silicon-containing compounds is silsesquioxane, characterized by a ratio of 1.5 between the silicon and oxygen atoms. In particular, polyhedral oligomeric silsesquioxane (POSS) was used as a reinforcing agent of a WPU used in the coating of wood [42].
Low-Dimensional Compounds for Diverse Material Sciences
Published in Kazuhiro Shikinaka, Functionalization of Molecular Architectures, 2018
Silsesquioxane-based polymer/oligomer also gives low- dimensional compound, which is polysilsesquioxane with ladder- shaped double-chain structure [14] or cage-shaped polyhedral oligomeric structure (POSS) [15]. Despite the same trifunctional RSiO3/2 unit, the filler effect of silsesquioxane for organic polymer is completely different depending on its structure. For example, increasing melt flow rate and noncombustibility of poly(phenylene ether) occur by an addition of not silsesquioxane with ladder- shaped double chain structure but POSS [16]. Contrastingly, silsesquioxane with ladder-shaped double chain structure itself behaves as a functional inorganic polymer that exhibits thermo- and radiation-resistant and mechanical properties derived from the defect-free siloxane (Si-O-Si) framework, which has high bond energy. Thus, silsesquioxane is expected to be used as a functional material according to its structural dimensions.
POSS-Containing Nanocomposite Polymer Coatings
Published in Vikas Mittal, Polymer Nanocomposite Coatings, 2016
Yasmin Farhatnia, Aaron Tan, Alexander M. Seifalian
Silsesquioxane is defined by the empirical chemical formula RnSinO1.5n, where R is an organic group (e.g., alkene) or hydrogen. Silsesquioxane structures can be generally classified as being either caged or noncaged. Noncaged structures can be further subdivided into random, ladder, and partial cage [6,7] (Figure 10.1). Caged structures include POSS [8]. POSS has a 3-D shape (polyhedral = many-sided) formed by a few (oligomeric) units of silsesquioxanes. The most common stoichiometric formula for POSS is R8Si8O12. Each POSS molecule measures 1.5 nm in diameter (including the –R groups) and it can be considered as the smallest achievable silica particle [9].
Research progress of ceramic matrix composite parts based on additive manufacturing technology
Published in Virtual and Physical Prototyping, 2019
Zhongliang Lu, Jiwei Cao, Zhaoqiang Song, Dichen Li, Bingheng Lu
Figure 3(a–c) shows the Cf/SiOC-SiC CMC porous structures fabricated by DIW technology (Franchin, Wahl, and Colombo 2017). The inks were formulated with a relatively large number of fibres (>30 vol.%), SiC powder and methyl-silsesquioxane. The methyl-silsesquioxane was used as both polymeric binder and ceramic source. And the carbon fibres play a dual role in composite materials: (1) Methyl-silsesquioxane has a significant density change and leads to a large volumetric shrinkage during pyrolysis process. However, there is little volumetric shrinkage of carbon fibres in this process. Therefore, stress is generated between the matrix and fibres which suppress the shrinkage of the matrix. (2) Toughness and strength of the material are improved. The compressive strength can be as large as 3.80 ± 1.23 MPa, at a high porosity of 75 vol.%. It can be observed from the fracture morphology that most of the carbon fibres are aligned along the extrusion direction (Figure 3(d,e)). Weak bonding connection between the carbon fibre and the ceramic matrix in the material results in fibre-pull-out and crack deflection which increase the mechanical properties of CMC. Table 1 summarises materials used for fabrication of CMC in DIW.
UV resistance graft modification of poly(p-phenylene-l,3,4-oxadiazole) fiber with polyhedral oligomeric silsesquioxane
Published in The Journal of The Textile Institute, 2018
Yahong Mao, Qingshuang Song, Yu Guan
γ-Aminopropyltrithoxysilane (from Debang New Chemical Materials Co., Ltd., Hubei, China), formaldehyde, tetrahydrofuran, hydrochloric acid, and sulfuric acid (all from Ke Long Co., Ltd., Chengdu, China) were analytically pure and were used as received. p-POD fiber was prepared in our laboratory and was described in our previous work (Zhang, Ye, Li, Li, & Xu, 2009; Zhang, Li, Ye, & Xu, 2007) To remove the oil and chemicals clinging to the fiber, it was scoured with acetone and ethanol at room temperature for 20 min respectively, washed repeatedly with hot and cold deionized water and dried under laboratory conditions. Octa-ammonium chloride salt of polyhedral oligomeric silsesquioxane (POSS-NH3Cl) was synthesized according to the procedures described in the References (Feher, Terroba, & Ziller, 1999; Feher & Wyndham, 1998) The resulting crude product was recrystallized with tetrahydrofuran. A white microcrystalline powder was obtained. The yield was 34.20%. The POSS chemical formula is shown in Scheme 2.