Effect of the surfactant coverage on the preparation of polystyrene–clay nanocomposites prepared by melt intercalation
Introduction
Polymer–clay nanocomposites have emerged as one of the most attractive engineering materials due to their unique properties. The basic properties of the nanocomposites such as mechanical and thermal are improved over a pristine polymer [1], [2], [3], [4]. The properties of polymer–clay nanocomposites are depending upon the formation of composite as reported by Kojima in 1993, the strength of nylon-6 clay composite is increased more than 50% and the heat distortion temperature improved from 65 to 145 °C [1], [2], [5], [6]. The formation of polymer–clay nanocomposites has been classified into three major types depending upon the dispersion of the clay in the polymer matrix. The first type is a conventional composite where the clay layers form an aggregate as a microparticle or tactoid. Second is the intercalated nanocomposite. The interlayer spacing of the clay layer is expanded by polymer insertion while the order of the clay layer is still maintained. The last one is exfoliated nanocomposites where the clay layer is delaminated as an individual layer and distributed randomly in the polymer matrix [7], [8], [9]. The goal of this study is to investigate the effect of the clay surface modification on its dispersion in polystyrene via melt intercalation [7].
Section snippets
Materials
Na-bentonite was obtained from Thai Nippon Chemical Co. Ltd. The surfactant used in this study is a mixture of dioctadecyl dimethyl ammonium chloride salts with alkyl chain lengths of 14 (4%), 16 (32%), and 18 (58%) and often referred as tallow alkyl ammonium. It will be referred as D18 throughout this study. The surfactant was obtained from Thai Specialty Chemical Co., Ltd. Polystyrene (GP 110) was obtained from Thai Petrochemical Industry Public Co., Ltd. Thailand. All the materials were used
Result and discussion
To understand the role of the clay surface coverage on the polystyrene–clay nanocomposites formation, two organoclay with different degrees of surface coverage were synthesized. The controlling of the surface coverage was done by treating the clay with the same surfactant but using a different surfactant loading. The surfactant is a mixed surfactant of the D18 surfactant. The organoclay was prepared by cation exchange reaction. Two loading levels at 0.5 and 2.0 mmol were used. They will be
Conclusion
The effect of clay surface coverage on the preparation of PS–clay nanocomposites by melt intercalation was investigated. Polystyrene shows a good affinity toward the organoclay with a lower surface coverage D1805 where the intercalated nanocomposites was observed. The clay with the high surface coverage hinders the formation of the nanocomposites due to poor wettability of the polystyrene on the clay surface. This leads to a phase separation between the polymer and the organoclay which results
Acknowledgement
Financial support from the Commission on Higher Education (Ministry of Education of Thailand) is gratefully acknowledged.
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