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Improved Thermal Stability of Organically Modified Layered Silicates

Published online by Cambridge University Press:  01 January 2024

Rick D. Davis ,
Jeffrey W. Gilman ,
Thomas E. Sutto ,
John H. Callahan ,
Paul C. Trulove  and
Hugh C. De Long
Rick D. Davis*
Affiliation:
National Institute of Standards and Technology, Building and Fire Research Laboratories, Gaithersburg, Maryland 20899-8665, USA
Jeffrey W. Gilman
Affiliation:
National Institute of Standards and Technology, Building and Fire Research Laboratories, Gaithersburg, Maryland 20899-8665, USA
Thomas E. Sutto
Affiliation:
Naval Academy and Naval Research Laboratory, Code 6170, Washington, DC 20375, USA
John H. Callahan
Affiliation:
FDA/CFSAN, HFS 717 Instrumentation and Biophysics Branch, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA
Paul C. Trulove
Affiliation:
Air Force Office of Scientific Research, 801 Randolph St. Room 732, Arlington, Virginia 22203-1977, USA
Hugh C. De Long
Affiliation:
Air Force Office of Scientific Research, 801 Randolph St. Room 732, Arlington, Virginia 22203-1977, USA
*
*E-mail address of corresponding author: rick.davis@nist.gov
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Abstract

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Bromide-containing impurities were found to decrease the thermal stability of quaternary alkyl ammonium-modified layered silicates. Improved purification procedures completely removed bromide and led to a 20°C to >100°C increase in organic modified layered silicate thermal stability. Using mass spectrometry and thermal and electrochemical analysis, N,N-dimethyl-N,N-dioctadecyl quaternary ammonium-modified montmorillonite and fluorinated synthetic mica were found to degrade primarily through elimination and nucleophilic attack by these anions. The nature of residual bromides was identified and quantified, and the efficiency of removing these anions was found to be solvent dependent; sequential extraction, first ethanol then tetrahydrofuran, gave the best results. This exhaustive extraction method represents a viable alternative to the use of expensive, more thermally stable oniumion treatments for layered silicates.

Keywords

Alkyl AmmoniumMontmorilloniteNanocompositesOrganic Modifier DegradationOrganoclaySynthetic Mica
Type
Research Article
Information
Clays and Clay Minerals , Volume 52 , Issue 2 , April 2004 , pp. 171 - 179
Copyright
Copyright © 2004, The Clay Minerals Society

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