Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites
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Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites A. Baran Inceoglu and Ulku Yilmazer Middle East Technical University, Chemical Engineering Department, 06531, Ankara, TURKEY
ABSTRACT Nanocomposites composed of unsaturated polyester matrix and organically modified clay filler were prepared. After the synthesis, XRD patterns showed that the interlayer spacing expanded from 1.25 nm to 4.5 nm. The mechanical properties of the nanocomposites were determined and it was found that adding only 3 w/w % organically modified clay improved the flexural modulus of unsaturated polyester by 35%. From DSC diagrams, it was found that Tg values of the nanocomposites also increased with the clay content. It is concluded that partially exfoliated / intercalated nanocomposites were formed at relatively low clay contents.
INTRODUCTION Nanocomposites with thermoplastic matrices have been synthesized and characterized [14]. Several studies have also been reported on nanocomposites with thermoset matrices. Lee and Jang [5] reported the characterisation of epoxy-clay hybrid composites prepared by emulsion polymerization. The effects of promoter and curing process on exfoliation behavior of epoxy/clay nanocomposites were studied by Ke, Lü, Yi, Zhao and Qi [6]. Kornmann, Linberg and Berlung [7] synthesized epoxy clay nanocomposites and analysed the nature of the curing agent on structure. Kornmann, Berglund and Giannelis [8] studied nanocomposites based on montmorillonite modified with silane coupling agent and unsaturated polyester. In the present study, the type and content of the montmorillonite (MMT) on mechanical and thermal properties are investigated using an unsaturated polyester (UP) matrix.
EXPERIMENTAL Organically treated montmorillonite (Cloisite® 30B from Southern Clay Products, USA) and non-treated Na-montmorillonite (Cloisite® Na+ from Southern Clay Products, USA) were used as the filler. Ortho-phthalic-general purpose unsaturated polyester (Neoxil C-92 N 8 from Camelyaf, Turkey) was used as the matrix. The resin and the matrix were first mixed mechanically for 3 hours at 50°C followed by ultrasonic mixing for better dispersion. 0.9 phr of methyl ethyl ketone peroxide (MEK-P) and 0.2 phr of cobalt naphthanate (as 8 % solution) were used as the catalyst and accelerator respectively. Flexural tests were performed according to the Test Method-I Procedure A of ASTM D790-92 using Lloyd 30k Universal Testing Machine with a crosshead speed of 2.8 mm / min. Pendulum Charpy Impact Tests were done according to the Test Method-I Procedure A in ASTM D256-91a using a Coesfeld Material device. In order to evaluate changes in Tg with increasing clay content, differential scanning calorimeter analyses were carried out using General V9.23.1
V4.1C DuPont 2000. Fracture surfaces were investigated by using JEOL JSM-6400 Scanning Electron Microscope (SEM). The fracture surfaces of pure UP and specimens containing MMT were compared. X-Ray diffraction patterns were recorded by monitoring the diffraction angle 2θ from 1°
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