Materials Science, Indian Association for the Cultivation of Science^* Department of Polymer Science & Technology, University College of Science and Technology, University of Calcutta, 92 A.P. C Road, Kolkata 700009, India.^**
○Suparna Sengupta^* Dipa Ray^** Siba Prasad Sengupta^*

Vinylester resin matrix composites were fabricated with 1%, 3% 5% and 10 weight% loading of organoclay respectively. The composite samples were subjected to various characterization techniques like X ray Diffraction, Flexural testing, Dynamic Mechanical Analysis, Thermogravimetric analysis, Differential Scanning Calorimetric analysis and Scanning Electron Microscopy. The clay samples as well as the clay/resin composites were investigated with X ray Diffraction studies. From the shift in the peak positions and the change in d-spacing values, it was evident that there was intercalation in the 3% and 10% composites, whereas some exfoliation occurred in the 1% and the 5% composites. The flexural strength and the breaking energy of all the composites were decreased compared to the unfilled resin, but there was an increase in flexural modulus value by 13%. From the dynamic mechanical analysis of the 3% and the 5% composites, it was observed that exfoliation (in 5% composites) raised the clay-resin interaction significantly, leading to an increase in the loss modulus value with a higher glass transition temperature compared to that of the intercalated sample (3% composites). Thermal degradation behaviour was also improved in the exfoliated sample compared to the intercalated one.