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Fire Retardancy and Morphology of Nylon 6-Clay Nanocomposite Compositions

Published online by Cambridge University Press:  26 February 2011

Kadhiravan Shanmuganathan
Affiliation:
g_kshanmugan@umassd.edu, University Of Massachusetts Dartmouth, Materials and Textiles, United States
Sandeep Razdan
Affiliation:
razdas@rpi.edu, Rensselaer Polytechnic Institute, Material Science and Engineering, United States
Nick Dembsey
Affiliation:
ndembsey@wpi.edu, Worcester Polytechnic Institute, Fire Protection and Engineering, United States
Quinguo Fan
Affiliation:
qfan@umassd.edu, University Of Massachusetts Dartmouth, Materials and Textiles, United States
Yong K Kim
Affiliation:
ykim@umassd.edu, University Of Massachusetts Dartmouth, Materials and Textiles, United States
Paul D Calvert
Affiliation:
pcalvert@umassd.edu, University Of Massachusetts Dartmouth, Materials and Textiles, United States
Steven B Warner
Affiliation:
swarner@umassd.edu, University Of Massachusetts Dartmouth, Materials and Textiles, United States
Prabir Patra
Affiliation:
ppatra@umassd.edu, University Of Massachusetts, Dartmouth, 285 Old Westport Road, North Dartmouth, Massachusetts, 02747, United States, 508-999-8439, 508-999-9169
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Abstract

We investigated the effect of organically modified clay on the thermal and flammability behavior of nylon 6 nanocomposites. We also used zinc borate along with layered silicate with an aim of achieving synergistic effect in flame retardancy. It is found that addition of 10 wt% clay reduced the onset decomposition (5% wt loss) temperature of nylon 6 by 20°C, while addition of 5 wt% zinc borate and 5 wt% clay in combination reduced it by around 10°C. Differential thermogravimetric analysis indicated that the peak decomposition temperature was not affected by the addition of clay, but the rate of weight loss decreased with increasing clay concentration. The horizontal burning behavior of the nanocomposite films of approximately 0.5mm thickness changed with additive concentration. The nanocomposites with 2.5 wt% and 5 wt% clay burned for almost the same duration as neat nylon 6 but dripping was reduced. The 10 wt% clay nanocomposite sample burned without any dripping and the flame spread rate was reduced by 25-30%. The burn rate of 5 wt % zinc borate/5 wt% clay nanocomposite sample was about 20% higher than that of 10 wt% clay nanocomposite sample, which could be attributed to varying char morphology. Scanning electron microscopy images of the 10wt% clay nanocomposite char surface and cross- section revealed an integrated layer of clay platelets with increasing density gradient from the center to the surface, while the 5 wt% zinc borate/5 wt% clay nanocomposite char appeared foamy and porous. The 5 wt% zinc borate and 5 wt% clay sample developed into a very good intumescent system in cone calorimeter test, swelling about 10-13mm height prior to ignition forming a cellular char structure. This was as effective as the 10wt% clay nanocomposite sample in reducing the heat release and mass loss rate of nylon 6 by around 65%. Fourier transform infrared spectroscopy of the 10 wt% clay nanocomposite char showed the presence of amides, indicating possible residual polymer within the shielded char.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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