Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Synthesıs and Characterization of Modified Organoclays for Polyolefıne-Clay Nanocomposites

In this study, the properties of organoclays obtained as result of the reactions between

3 different cationic surface active agents with different concentrations and montmorillonite.

Hexadecy trimethyl ammonium bromide, dimethyl dihydrogenated tallow amonium chloride and octadecyl ammonium chloride are used as cationic surfactants. Montmorillonit is used as clay and was supplied from BENSAN Aktifleştirilmiş Bentonit Sanayi ve Ticaret A.Ş.

Organoclay is synthesized which is result of reaction between montmorillonite and three different surfactants with different concentrations (equivalent of Cation Exchange Capacity of the clay, 2 times and 3 times of the CEC equivalent). Temperature and total volume of the reaction medium are stable during the reaction time. After the reaction, organoclay suspansion are filtered under vacuum and washed several times with destilled water until no Cl- or Br- ions were detected by AgNO3 titration and filtered. Following this step, modified montmorillonite was dried and grinded.

The structural and physical properties of the reaction products were investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Differential Thermal Analysis (DTA) and Scanning Electron Microscopy (SEM).

The absorbtion peaks of unmodified and modified montmorillonites are investigated by FTIR. The peaks which  are belong to cationic surfactants in orgonaclay structure are determined. This indicates that modification of clay was carried out succesfully. Furthermore,

Amounts of surfactants which are absorbed to montmorillonite depending on reaction conditions by compareing the peak intensities of organic structures with a reference peak of montmorillonite.

Using XRD analysis, the distances between layers of organoclays were investigated. Depending on chain length and concentration of cationic surfactant, increase in distance between montmorillonite layers are observed.

Three degradation stages were determined on reaction products by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The first stage is loss of free and interlayer water (dehydratation) before 100 oC, the second stage is; decomposing of organic substaces sorbed on montmorillonite between 200-500 oC and the last stage is dehydroxlation in the temperature range 500-800 oC where the hydroxyl groups, which is covalently incorporated in the silicate layers, is dehydrated. These stages are clearly observed at TGA-DTA, TGA-DTG and DSC Analysis.