Title: RHEOLOGICAL BEHAVIOUR OF STYRENE-FREE UNSATURATED POLYESTER-CLAY NANOCOMPOSITES
Page Range: p.101-110
Author(s): Amir Masoud Rezadoust; Masoud Esfandeh; Mohammad Hosain Beheshty
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 21
Issue No: No.2
Abstract
The rheological behaviour of styrene-free unsaturated polyester resin-organoclay (Cloisite 15A) nanocomposites at various clay contents, prepared by melt mixing, was investigated. Styrene-free resin was used to achieve high-shear mixing and to avoid viscosity changes due to solvent evaporation. In order to compare the effects of shear- and diffusion-induced phenomena on the intercalation of nanoclay; samples were prepared at two different temperatures of 40 degrees C (cold-mixed) and 150 degrees C (hot-mixed) and tested in the range of 40-120 degrees C using dynamic rheometry. Complex viscosity-temperature curves for cold-mixed samples showed a decrease in viscosity with increasing temperature followed by the formation of a plateau at a particular temperature, depending on the clay content. This behaviour is characteristic of systems with a network structure. The results of small angle X-ray diffraction and TEM analysis confirmed the intercalation of the nanoclay particles as well as a reduction in their thickness. TEM images revealed that the size reduction happened through bending fracture followed by shear delamination of the fractured clay layers. On this basis, a structure of the physical network was proposed to be formed by sticking several nanoclay stacks inside a polymer chain and more involvement of polymer chains with the delaminated layers’ ends. A dispersion model was used to quantify and interpret the dispersion status of nanoclay particles in the resin system. 27 Refs.