- Author
-
Davis, R. D.
|
Gilman, J. W.
|
Sutto, T. E.
|
Callahan, J. H.
|
Trulove, P. C.
|
DeLong, H. C.
- Title
- Improved Thermal Stability of Organically Modified Layered Silicates.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
Naval Academy and Naval Research Laboratory, Washington, DC
FDA/CFSAN, College Park, MD
Air Force Office of Scientific Research, Arlington, VA
- Journal
-
Clays and Clay Minerals,
Vol. 52,
No. 2,
171-179,
2004
- Keywords
-
silicates
|
thermal stability
|
nanocomposites
|
degradation
|
additives
|
x-ray diffraction
|
mass spectroscopy
|
thermogravimetric analysis
- Identifiers
- alkyl ammonium; montmorillonite; organoclay; quaternary alkyl ammonium; synthetic mica; organic modifier degradation
- Abstract
- Bromide containing impurities were found to decrease the thermal stability of quaternary alkyl ammonium modified layered silicates. Improved purification procedures completely removed these bromide anions and led to a 20 °C to > 100 °C increase in organic modified layered silicate thermal stability. Using mass spectroscopy, 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 quantified, and the efficiency of removing these anions was determined 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.