Poly(ethylene glycol)-grafted silica nanoparticles for highly hydrophilic acrylic-based polyurethane coatings

• Published in: Progress in organic coatings 2017-05, Vol.106, p.145-154
• Main Authors: Lin, Baozhong, Zhou, Shuxue
• Format: Article
• Language: English
• Subjects: Acrylic-based polyurethane; Chemical bonds; Chemical synthesis; Coatings; Contact angle; Coupling (molecular); Coupling agents; Dirt; Dirt-resistance; Hydrophilic coatings; Hydrophilic surfaces; Hydroxyl groups; Infrared analysis; Nanocomposites; Nanoparticles; Poly(ethylene glycol); Polyethylene glycol; Polyurethane; Polyurethane resins; Silica; Silica nanoparticles; Silicon dioxide; Thermogravimetric analysis
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2017.02.008

•SiO2-PEG nanoparticles bearing terminal hydroxyl groups was synthesized.•SiO2 nanoparticles bonded with lower Mn PEG have better hydrophilic additive effect.•Highly hydrophilic PU coatings with WCA of 38.7° was obtained after water-inducing.•SiO2-PEG embedded APU coatings have better dirt resistance outdoors. A silane coupling agent bearing poly(ethylene glycol) (PEG) chains was synthesized using triethoxysilylpropyl isocyanate and excess PEG, with molecular weights of 400 or 1000g/mol (PEG400 and PEG1000) and chemically bonded to SiO2 nanoparticles, to obtain PEG-modified SiO2 nanoparticles (SiO2-PEG) with pendant hydroxyl groups. The PEG modification was demonstrated by Fourier transformed infrared spectroscopy, thermogravimetric analysis, and through the dispersion behavior of SiO2-PEG nanoparticles in water. The SiO2-PEG nanoparticles were further incorporated into acrylic-based polyurethane (APU) coatings. Transparent and crack-free nanocomposite coatings with SiO2-PEG content up to 35 and 40wt.% were achieved for SiO2-PEG400 and SiO2-PEG1000, respectively. The high quality of the product was owed to the improved compatibility of SiO2 nanoparticles with the APU matrix after PEG modification. Due to the rearrangement of hydrophilic/hydrophobic segments, a highly hydrophilic surface, with a water contact angle (WCA) as low as 38.7°, was attained for the SiO2-PEG embedded coatings after induction with water. Moreover, SiO2-PEG400 was more efficient in enhancing the surface hydrophilicity of the APU coatings than SiO2-PEG1000 at the same SiO2-PEG content. In contrast, pure APU coatings and the APU coatings containing unmodified SiO2 nanoparticles displayed WCAs of 68.2° and 70.1°, respectively. Outdoor exposure experiments showed that the APU coatings containing SiO2-PEG nanoparticles had excellent dirt-resistance.