Studies on Effect of Organoclay and Melamine Powder on Flexible Polyurethane Foam for Aerospace Applications

Abstract

Flexible polyurethane foam (PU) is a suitable candidate for various aerospace applications like acoustic insulation due to its high flexibility, ease of processing, etc. But one of the major disadvantages of this foam is low flammability resistance. The aim of this study is to improve the flame resistant properties of flexible PU foam through incorporation of additives. Flexible polyurethane foams were synthesized through one shot process with organically modified nanoclay and melamine powder as respective fillers. Foam incorporated with fillers were characterised spectroscopically, morphologically and thermally. Subsequent to this, cured foam was subjected to density, water absorption, rebound resilience, and thermal conductivity evaluation. The flammability and limiting oxygen index analysis of the melamine added foams were characterised to ensure the flame resistance of the foam. Outgassing properties such as total mass loss and collected volatile condensable material were also inferred as these foams are intended for aerospace applications. The incorporation of organo-clay in PU flexible foam has an optimistic effect on thermal stability, bulk density and cell diameter. However, modification of PU foam through melamine powder incorporation does not have any effect on the thermal stability. Although excellent flame retardancy was obtained for foams with melamine as filler, high outgassing properties observed, due to the higher liberation of nitrogen gas and other volatiles which limits their applications in space craft areas. These studies revealed that organoclay modified flexible polyurethane foam can be selected as the best candidate for aerospace application as it meets all the requirements without compromising its inherent properties.