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A novel method was used to synthesis nanosilica/waterborne polyurethane (WPU) hybrids by in situ hydrolysis and condensation of tetraethyl orthosilicate (TEOS) and/or 3-aminopropyltriethoxylsilane bonding at the end of the WPU molecular chain. The hybrid was characterized by scanning electron microscopy, energy dispersive spectroscopy (EDS), transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results showed that the nanosilica/WPU hybrids with well-dispersed nanosilica particles were synthesized, in which the particles had typical diameters of about 50 nm. In addition, XPS and FTIR analyses demonstrated that chemical interaction occurred between WPU and silica. The effects of TEOS on surface wettability, water resistance, mechanical strength, and thermal properties of the hybrid were also evaluated by contact angle measurements, water absorption tests, mechanical tests, and differential scanning calorimetry, respectively. An increase in advancing contact angles, water resistance, and tensile strength, as well as decrease in elongation at break and glass transition temperature, were obtained with the addition of TEOS. Water absorption decreased from 17.3 to 5.5%. The tensile strength increased to a maximum of 29.7 MPa, an increase of about 34%. Elongations at break of the hybrids decreased 191%. These results were attributed to the effects of the nanosilica and the chemical interaction between WPU and silica. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

A novel in-situ nano hybrid technique combined with industrialized wet phase inversion coating-forming process was developed for the modification of polyurethane (PU) leather coating with nano-SiO2. During the wet phase inversion process, nano-SiO2 particles were in-situ generated synchronously as polyurethane resin coagulated. Scanning electron microscope analysis indicated that when the SiO2 concentration was limited within 1.5 wt%, the size scale of in-situ generated nano-SiO2 ranged from 70 to 150 nm, which were well-separated and dispersed uniformly throughout the PU coating. After nano hybridization, extra mesopores were detected in the PU coating by nitrogen adsorption/desorption experiment. These mesopores were correlated with enhanced water vapor and gas (hydrogen, nitrogen, and oxygen) permeability, which could improve the breathability or wear comfort of PU leather. In spite of extra mesopores, the hybrid PU coating maintained comparable hydrostatic pressure to control. Nevertheless, when the SiO2 concentration was increased up to more than 1.5 wt%, micro-SiO2 particles and agglomerates dominated throughout the PU coating, which obstructed mass transportation and lowered the breathability of the coating. Without disturbing established wet phase inversion coating-forming process in PU leather industry, the novel in-situ nano hybrid technique developed in this study may be of great potential for producing PU leather with improved breathability on an industrial scale. [ABSTRACT FROM AUTHOR]

Abstract: A novel method was employed to synthesize TiO2–SiO2/waterborne polyurethane (WPU) hybrid terminated by 3-aminopropyltriethoxylsilane (APTES) via a sol–gel process. The hybrids were synthesized by in situ hydrolysis and condensation of tetrabutyl titanate (TBOT) and APTES. TiO2–SiO2 particles were well dispersed in polymer matrix with a diameter of about 500nm and there was no phase separation between particles and WPU. XPS analysis demonstrated that TiOSi bonds existed in TiO2–SiO2/WPU hybrid, and the percentages of SiOTi bond in Si and Ti were about 35% and 20%, respectively. The chemical bonds between WPU and TiO2–SiO2 facilitated the homogenous dispersion and better compatibility during the sol–gel process. The successful preparation of TiO2–SiO2/WPU hybrid opens a new way to investigate other inorganic particles/WPU hybrids, such as Al2O3–SiO2/WPU for coating, fiber and adhesive applications. [Copyright &y& Elsevier]