Abstract
This study focused on the deintercalation of dimethyl sulfoxide (DMSO) from a kaolinite–DMSO complex in various solvents. The use of kaolinite as filler in polymer–clay composite generally faced the difficulty of kaolinite dispersion due to its high cohesion. For improved dispersion of kaolinite within a given matrix, previous intercalation of small polar molecules is usually done prior to its displacement during composite-making. The influence of the solvent polarity on the deintercalation in analyzed here to understand its role during the deintercalation process. The intercalation of the DMSO was done by solution-mixing and its displacement was done in distilled water, ethyl acetate, and acetone. The products of deintercalation were analyzed using Fourier transform infra-red (FTIR), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The weakening of the kaolinite cohesion after DMSO intercalation is demonstrated through the broadening of the diffraction peak associated with the kaolinite on XRD patterns. From FTIR spectra, the weakening is associated with the displacement to low wavenumbers of the Si–O or Al–O vibration bands within the kaolinite–DMSO complex. The kaolinite dehydroxylation temperatures from DSC show that the rate of DMSO displacement affects the ordering of the recovered kaolinite. The crystallite size of the kaolinite is reduced from the raw to the recovered kaolinite after DMSO displacement, indicating an exfoliation of the kaolinite. From these results, it is found that the removal of the DMSO from the kaolinite–DMSO complex is influenced by solvent polarity. The higher the polarity, the greater the removal of the DMSO from the complex. Solvent polarity affects the rate of DMSO displacement, which influences the ordering of the recovered kaolinite. It is suggested that solvent polarity can be used to control the removal rate of DMSO, which may be key to the dispersion of the kaolinite platelets.
Highlights
Clays are industrial materials used in many domains, such as paints, inks, rubbers, ceramics, and building materials
The crystallite size is small in kaolinites recovered after dimethyl sulfoxide (DMSO) removal, indicating an exfoliation of the kaolinite layer after intercalation–deintercalation, and their values do not vary with the solvent used
Solvent polarity affects the rate of the DMSO removal, and this affects the structure of the recovered kaolinite
Summary
Clays are industrial materials used in many domains, such as paints, inks, rubbers, ceramics, and building materials. The asymmetric structure of the kaolinite layer, due to the overlay of tetrahedral and octahedral sheets within the layer, induces strong superimposed dipoles that, together with hydrogen bonds between the silica ring and the aluminum surface, give a strong cohesive energy to the mineral [10,11] This cohesive energy makes the kaolinite layer almost non-expansive, and poorly dispersible. Some recent works indicates that the use of kaolinite can be improved if convenient dispersion is achieved [3,9,25] These studies used kaolinite–DMSO as an intermediate to improve the dispersion of clay within a polymer matrix. The study of kaolinite–DMSO complexes shows that the intercalated molecule influences H-bonding within the kaolinite layer, which results in a less cohesive structure [12]. X-ray diffraction (XRD), Fourier transform infra-red (FTIR), and thermal analysis were used to analyze the kaolinite–DMSO intercalate and the products of deintercalation
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