Effects of additives in colloidal silica based inorganic-hybrid binder for mineral wool insulation boards

In the mineral insulation board industry, it has been a challenge to replace the current organic binder to eco-friendly inorganic binder to enhance the fire-resistance, and reduce toxicity. Inorganic and hybrid (organic-inorganic) type materials are often used, but the effects of these binders on the properties of the insulation board are little understood when applied to ceramic wool. In this study, silica-sol base binders with additives such as fumed silica, silicates, methyltrimethoxy silane, or polysiloxane are utilized. The inorganic-hybrid binders are used to understand how they change the microstructure, and how these changes in microstructure influence the insulation board properties. The effects of (i) the morphology of silica, (ii) adding alkali-silicates, and (iii) adding network modifiers are investigated for silica-sol type binders by assessing properties of fabricated boards, such as thermal conductivity, compressive strength, and water absorption rate. In particular, for a binder of colloidal silica with silicate and polysiloxane, we found that this binder forms clot-like hubs at junctions while embedding fibers. Thus, this structure allows the insulation board to withstand higher compression stress while having equivalent thermal insulation and waterproof performance as a phenolic binder.