Organosiloxane reactivity on dehydroxylated silica surfaces

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:258301

Grabbe, A; Michalske, T A ^[1]

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1. Sandia National Labs., Albuquerque, NM (United States)

In most cases, the surface reactivity of silica glass is controlled by the presence of silanol groups. However, glass surfaces that are produced by high temperature forming processes possess little if any silanol groups. Previous work demonstrated that the reactivity of glass surfaces formed at high temperature is controlled by the existence of strained siloxane rings. In this study, the authors conducted experiments on highly dehydroxylated silica powder surfaces and silica surfaces that were formed directly from the melt to explore the reactivity of strained siloxane rings with various organosiloxanes reactants. The authors use infrared spectrometry to show that strained dimer rings react with organosiloxane molecules or with water at comparable rates, depending on the structure of the organosiloxane. The data indicate that the important features of the reacting molecule are its polarity, steric accessibility and bond strain. Since the measured reactions require approximately six orders of magnitude of gas exposure to go from 1% to 99% completion, these data present strong evidence that the surface is highly heterogeneous. By applying a linear distribution of activation energies, the authors estimate that spread in activation energy to be approximately 40 kJ/mole. In this presentation, the authors discuss the implications of this newly discovered silica chemistry for novel approaches to tailor melt-formed surfaces for improved polymer adhesion and hydrolytic stability. They will also discuss efforts to prepare true melt-formed surfaces by blowing bubbles of silica in a vacuum environment.

• Research Organization: Sandia National Laboratory
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 258301
• Report Number(s): CONF-9506225--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
ABSORPTION SPECTROSCOPY
ACTIVATION ENERGY
CHEMICAL REACTIONS
PRODUCTION
SILICA
SILOXANES