Downloaded by UNIV OF DELAWARE MORRIS LIB on June 26, 2012 | http://pubs.acs.org Publication Date: April 27, 2009 | doi: 10.1021/bk-2009-1013.ch005
Chapter 5
Effect of Flame Retardants on the Thermal, Burning, and Char Formation Behaviour of PolypropyleneNanoclay Compounded Polymers 1
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Baljinder K. Kandola , A. Yenilmez , Richard A. Horrocks , G. Smart , W. Kun2, and Yuan H u 1
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1Centre for Materials Research and Innovation, University of Bolton, Bolton BL3 5AB, United Kingdom 2State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, People's Republic of China The effect of different flame retardant types on the thermal stability, flammability and char formation tendency of polypropylene (PP) nano/micro composite is studied. PP, compatabiliser, nanoclay, UV-stabiliser and different flame retardants have been compounded in a twin screw extruder to produce polymers with improved thermal and flame retardant properties. Thermal analysis has been used to study the thermal properties, and limiting oxygen index (LOI) and slightly modified UL-94 test for flammability of the samples. All flame retardants acting in the condensed phase (phosphorus- and nitrogen- containing) lowered the rate of decomposition, whereas halogenated flame retardants had a little effect. The addition of nanoclay with or without flame retardants increased the thermal stability of all samples and helped in char formation. All samples with flame retardants and no clay, burnt completely, which is not unexpected, given the low levels (5%) of flame retardants used here. However, the flame spread was low. On addition of clay to the compounded polymer, a change in burning behaviour was observed, flame spread was reduced and samples self-extinguished, except for the one containing melamine phosphate. A tube furnace was used for char formation at different temperatures and the charred structures have been © 2009 American Chemical Society
In Fire and Polymers V; Wilkie, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
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48 examined with digital images, optical and scanning electron microscopy, and FTIR. This information has been used to understand the mechanisms of thermal degradation of different flame retarded PP - nano/micro composite samples.
Downloaded by UNIV OF DELAWARE MORRIS LIB on June 26, 2012 | http://pubs.acs.org Publication Date: April 27, 2009 | doi: 10.1021/bk-2009-1013.ch005
Introduction Polypropylene or polypropene (PP) is a useful commodity polymer mainly used in apparel, upholstery, floor coverings, medical, geotextiles and automotive applications, due to its low cost, light weight, good mechanical properties and low reactivity towards other chemicals. The main advantage is that PP being an addition polymer made from the monomer propylene, is unusually resistant to many chemical solvents, acids and bases. However, being wholly aliphatic hydrocarbon structure, burns very rapidly with a relatively smoke-free flame and without leaving any char residue (1). Lack of polar groups in the structure makes it difficult to react with reactive flame retardants. Additive flame retardants i f used, are required in large amounts (>20% w/w) to provide the required fire protection to products (1). However, such high levels of additives cause polymer processing problems, in particular for their extrusion into thin films or fibres. The recent developments in the area of polymer - nanocomposites have suggested that by the addition of just a small quantity (
