Manufacturing of Silica Glass from Silica Powder Consolidated with Tetramethoxysilane Oligomer-derived Binder (II). Role of Tetramethylammonium Hydroxide as a Catalyst for Binder Synthesis

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The role of a catalyst during the synthesis of a binder, which could harden a silica slurry, was investigated. Tetramethoxysi1ane oligomer was efficiently hydrolyzed and poly-condensed to the binder when tetramethylammonium hydroxide and tetraethylammonium hydroxide, which are both organic bases having bulky groups, were used as catalysts. On the other hand, nitric acid, sodium hydroxide, potassium hydroxide and ammonia were not effective catalysts for binder synthesis. The difference in the role between these catalysts was explained as follows. The bulky organic groups were assumed to have a steric hindrance interaction with methyl groups in tetramethoxysilane oligomer and this steric interaction could successfully produce the binder.