The property and formation mechanism of unsaturated polyester-layered silicate nanocomposite depending on the fabrication methods

The properties of unsaturated polyester (UP)/montmorillonite (MMT) nanocomp osite greatly depend on the preparation procedure because of the chemical r eactions and physical interactions involved. To investigate the properties and formation mechanism of UP/MMT nanocomposite, samples were prepared by t wo different mixing methods. The first method, simultaneous mixing, is simi lar to the method used for preparing the conventional unsaturated polyester and filler composite. The second method is the sequential mixing, a new ap proach for preparing unsaturated polyester-layered silicate nanocomposite. In the first step, pre-intercalates of the unsaturated polyester and MMT na nocomposites were prepared. In other words, mixture of the UP and organophi llic-treated MMT are prepared in the first step; a styrene monomer was then added to the pre-intercalates of UP/MMT with varying mixing time. The stru ctures of UP/MMT nanocomposite were investigated by X-ray diffraction and t ransmission electron microscopy. To investigate the formation mechanism of UP/MMT nanocomposite, dynamic mechanical thermal analysis, solution-rheomet ry and melt-rheometry were performed. The properties and formation processe s depending on two methods are compared. These tests enable us to understan d the mechanism of UP-silicate nanocomposite formation. Based on this mecha nism, we have been able to increase the crosslinking density and the degree of dispersion in UP/MMT nanocomposite. (C) 2000 Published by Elsevier Scie nce Ltd.