Interfacial modification of polystyrene-block-polybutadiene-block-polystyrene/ magnesium hydroxide composites, 1-effect on rheological properties

Liauw, Chris, Lees, Graham C., Dumitru, Paul, Clemens, Mark L. and Rothon, Roger N. (2003) Interfacial modification of polystyrene-block-polybutadiene-block-polystyrene/ magnesium hydroxide composites, 1-effect on rheological properties. Macromolecular Materials and Engineering, 288 (5). pp. 412-420. ISSN 1439-2054

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Abstract

Composites based on polystyrene-block-polybutadiene-block-polystyrene (SBS triblock thermoplastic elastomer) and magnesium hydroxide (Mg(OH)2) (5-60 wt.-%) have been prepared by twin screw extrusion. Interfacial modifiers included dispersants, i.e., isostearic acid, oleic acid, stearic acid; and coupling agents, i.e., maleanised polybutadiene and vinyltriethoxysilane. In each case, approximately one monolayer of treatment was used. A dual bore motor driven extrusion rheometer was used for assessment shear and elongation flow behavior (Cogswell's method) over a shear rate range of 100 s-1 to 5 000 s-1. Untreated filler and filler treated with coupling agents gave composites that become increasingly pseudoplastic as filler level increased. Fatty acid structure was shown to have some influence over the level of melt viscosity reduction normally associated with such treatments; stearic acid gave the most pronounced reduction in melt viscosity possibly due to the tightly packed monolayer. Elongational flow properties, determined using Cogswell's method, indicated significant chain extension/branching of the bulk matrix when high levels of untreated filler were present and long range filler-matrix interaction in composites modified with maleanised polybutadiene.