Heat and fire resistance of polyurethane-polydimethylsiloxane hybrid materials

This work examines the synthesis of polyurethane (PU)-polydimethylsiloxane (PDMS) hybrid in order to provide low flammability to PU. Chemical characterization of PU/PDMS hybrid by solid state NMR of carbon and FT-IR shows that some PDMS segments are incorporated in the macromolecular chains of PU. Heat stability of PU (thermo-oxidative decomposition) is not enhanced by the incorporation of PDMS except that the amount of the high temperature residue is improved and depends on the amount of PDMS incorporated in the PU chains. It is explained by the formation and the accumulation of silica. On the contrary, thermal stabilization (charring) occurs in the pyrolytic conditions when incorporating PDMS. The accumulation of silica as well as charring enhancement enables the flammability properties of the PU/PDMS hybrid to form a protective layer limiting heat transfer between the flame and the substrate. The heat release rate measured by cone calorimetry of PU/PDMS hybrid is significantly decreased compared to virgin PU and temperature of the back of the sample is comparatively low compared to virgin PU. Copyright (C) 2006 John Wiley & Sons, Ltd.