Photocurable epoxy/cubic silsesquioxane hybrid materials for polythiourethane: Failure mechanism of adhesion under weathering

Abstract

A new inorganic-organic hybrid coating containing epoxy-functionalized cubic silsesquioxane (CSSQ) has been developed, which can be polymerized cationically by UV radiation. This solvent-free solution can be used as hybrid coating for polythiourethane (PTU) substrate. The surface properties of the coating film were determined by adhesion and scratch resistance. The excellent adhesion of coating films on the substrate was observed at the initial stage before weathering, but deteriorated after exposure to the sunshine. The low viscosity of hybrid coating solution ($ 15 mPa s) leads to fast curing and the formation of hybrid coating film during the photopolymerization reaction. The adhesion failure was evaluated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. AFM images showed that the surface is smooth at the initial stage, but a texture surface was developed after weathering. The shrinkage of the hybrid film due to the increase in crosslinking density by postpolymerization would affect the surface roughness after weathering. XPS analysis indicated that the adhesion failure occurred by photodegradation of the PTU substrate during weathering. The weathering resistance was significantly improved by adding UV absorbers, which protected the polymer substrate from the photodegradation. The advantages of the hybrid coating include fast cure speed, solvent-free formulation, and improved surface properties of the coating film.

Recent Developments in the Chemistry of Cubic Polyhedral Oligosilsesquioxanes

“…The viscosity of T 8 (OSiMe 2 R) 8 compounds, where R = (CH 2 ) 3 OCH 2 CH(O)CH 2 , (CH 2 ) 2 C(O)C(CH 2 )Me, and OSiMe 2 OSiMe 2 H have been measured and found to be ca. 600, 220, and 200 mPa s. These values are similar to some engine oils, but the compounds are not chemically robust enough for such use. , The relative viscosity as a function of concentration in hexane for T 8 ( i -Bu) 7 (CH 2 ) 3 NHC(O)C 6 H 3 -3,5-(OCN) 2 has been plotted and the extrapolated intrinsic viscosity found to be 0.005 ± 0.002 dL g −1 , which is consistent with a size of ca. 1 nm for the molecule …”

Enhanced adhesive and mechanically robust silicone‐based coating with excellent marine anti‐fouling and anti‐corrosion performances

“…The content of S element on the surface of PTUBAF coating is higher that of the surface of PTU and PTUF (Table S2), illustrating that the surface of PTUBAF coating contains the isobornyl group. Two characteristic peaks located at 398.5 eV and 399.2 eV are ascribed to −NH− and C−N in Figure 3c, [24] respectively. These peaks occur due to the reaction of −NCO with −OH, which further corroborates the existence of −NHCOO−.…”