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Assessment of extrusion-sonication process on flame retardant polypropylene by rheological characterization

1 CIATEC, A.C., Omega 201, León, Gto. 37545, Mexico
2 Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Mexico city 04510, Mexico
3 Facultad de Química, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Mexico city 04510, Mexico

Topical Section: Advanced composites

In this work, the rheological behavior of flame retardant polypropylene composites produced by two methods: 1) twin-screw extrusion and 2) ultrasound application combined with a static mixer die single-screw extrusion is analyzed in detail; results are related to the morphology of the composites. The flame retardant polymer composites are composed of a polypropylene matrix, an intumescent flame retardant system and functionalized clay. Scanning electron microscopy revealed that the combination of the static mixer die and on-line sonication reduced particle size and improved the dispersion and distribution of the intumescent additives in the polypropylene matrix at the micrometric level. From linear viscoelastic properties, the Han, Cole-Cole and van Gurp-Palmen diagrams characterized the improved particle dispersion of the flame retardant additives. Two well-defined rheological behaviors were observed in these diagrams. These behaviors are independent on clay presence and concentration. In fact, the ultrasound device generates a 3D highly interconnected structure similar to a co-continuous pattern observed in polymer blends as evidenced by rheological measurements. This improvement in the dispersion and distribution of the additives is attributed to the combined effect of the static mixer die and on-line sonication that allowed reducing the additive content while achieving the optimum classification UL94-V0.
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Copyright Info: © 2016, Guadalupe Sanchez-Olivares, et al., licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution Licese (http://creativecommons.org/licenses/by/4.0)

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