Where ppm Quantities of Silsesquioxanes Make a Difference—Silanes and Cage Siloxanes as TiO2 Dispersants and Stabilizers for Pigmented Epoxy Resins

Abstract

In this work, silsesquioxane and spherosilicate compounds were assessed as novel organosilicon coupling agents for surface modification of TiO2 in a green process, and compared with their conventional silane counterparts. The surface-treated TiO2 particles were then applied in preparation of epoxy (EP) composites and the aspects of pigment dispersion, suspension stability, hiding power, as well as the composite mechanical and thermal properties were discussed. The studied compounds loading was between 0.005–0.015% (50–150 ppm) in respect to the bulk composite mass and resulted in increase of suspension stability and hiding power by over an order of magnitude. It was found that these compounds may be an effective alternative for silane coupling agents, yet due to their low cost and simplicity of production and manipulation, silanes and siloxanes are still the most straight-forward options available. Nonetheless, the obtained findings might encourage tuning of silsesquioxane compounds structure and probably process itself if implementation of these novel organosilicon compounds as surface treatment agents is sought for special applications, e.g., high performance coating systems.

Novel Multifunctional Spherosilicate-Based Coupling Agents for Improved Bond Strength and Quality in Restorative Dentistry

“…Silicon presence comes from microsilica filler; zirconium from zirconia used mostly as an RTG contrasting agent; titanium from TiO 2 pigment used to balance the composite color; all these elements are in form of oxides, which is visible on oxygen EDS map. The oxides contain hydroxyl surface groups, which allow for chemical reaction with a silane or spherosilicate-based coupling agent (primer) [ 20 ].…”

“…Spherosilicate compounds were prepared according to literature reports: octahydrospherosilicate [ 29 ]; mixed group spherosilicates [ 20 ].…”

“…The idealized structures of these compounds are given in Figure 2 . It was found previously that for mixed groups SS compounds synthesis carried out by hydrosilylation route, a series of congeners is in fact generated, with the desired structure being the predominant, but not exclusive one, due to the normal distribution of the possible products [ 20 ]. Additionally, for the detailed NMR study purposes, SS-8MA derivative was synthesized under the same conditions as a spectroscopic standard for the study, to assign all the observed signals and resolve the structure of all the main and side products formed during allyl methacrylate hydrosilylation.…”

“…Both SSQ and SS compounds are spherical oligomeric species with multiple active centers, which can be modified with various substituents such as alkoxysilyl, methacryl, vinyl groups and many others, unreactive organic functional groups, which help SSQ molecules become soluble in, or compatible with, polymers [ 1 , 2 ]. Reactive groups enable SSQs and SS to serve as silane coupling agents for surface modification of inorganic fillers, as well as a reactive component of curable resins [ 20 ]. Adding such molecules to composite structure can greatly influence the physical properties, volumetric shrinkage, flexural strength, young modulus [ 21 ], biocompatibility and reduced inflammatory response [ 22 ].…”

Improving the Dispersibility of TiO2 in the Colloidal System Using Trifunctional Spherosilicates

“…The variation of surface nature was also observed when titanium dioxide was functionalized with sodium stearate and sodium oleate [ 17 ]. Recent studies have shown that the use of functionalized silsesquioxanes as modifiers of TiO 2 increased its hydrophobicity and improved covering and dispersing properties [ 18 ].…”