The preparation and characterization of PEK/TEOS glasses by the sol-gel method
Noell, John Lee Watson
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Over the last twenty years, substantial emphasis has been placed on the development of a new class of inorganic glasses using the sol-gel approach. This technique utilizes metal alkoxide precursors such as tetraethylorthosilcate (TEOS) to build an inorganic glass matrix out of solution by a two step poly(hydrolysis-condensation) reaction mechanism. The benefits of making ceramics by this method include considerable energy savings due to the lower sintering temperatures required to form the densified glass and the ability to produce multi-component amorphous materials that can not be made through the traditional firing processes. As a result of this last possibility, polymer researchers have sought to develop spin-off hybrid inorganic-organic network systems that can be prepared by the sol-gel method using reactively functionalized oligomers and/or monomers along with the metal alkoxide precursors. These types of organically modified multi-component glasses could have enormous potential from an applications standpoint because the systemâ s mechanical and physical features can be tailored in accordance to the organic and polymeric materials chosen. One such inorganic-organic system prepared by this procedure is the new PEK/TEOS glasses. The PEK represents the bisphenol-A polyarylene ether either ketone thermoplastic polymer endcapped with triethoxysilane functional groups. By mixing the PEK and TEOS components at different weight compositions in the starting sol-gel reaction solution, change in the mechanical properties is observed as the TEOS content is increased for the final, thin film glasses. Also, a poor extent of reaction or degree of incorporation of the PEK oligomer is revealed which has been attributed to the vitrification of the glass before the PEK endgroups have a chance to react. To alleviate this problem, thermal treatments are employed to further the sol-gel reaction and to complete the network formation in the PEK/TEOS glasses. After the thermal treatments, the change in the mechanical and physical properties are monitored, and the data retlects systematic trends in regards to the TEOS content and the temperature of the thermal treatment utilized. In addition to these results, some speculative information is provided on the temperature sensitivity and the rate of curing of the PEK/TEOS glasses during the thermal treatments.
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