Intumescent flame retardant systems of modified rheology

A model system of intumescent flame retardants, consisting of ammonium polyphosphate and pentaerythritol was prepared and investigated in polypropylene and without the polymer matrix. Thermal scanning oscillation rheometric investigation in the temperature range of 170-500 degreesC was used to detect the rheological behaviour in the region of melting of the polymer and the plasticity of the char formed at higher temperature. Addition of boroxo siloxane to the model system caused advantageous changes in both regions. Increased complex viscosity and viscoelsasticity of the melt and char respectively contributes to better flame retardancy. According to DTG and FTIR studies the reactions of boroxo siloxane with pentaerythritol and ammonium polyphosphate are the reasons for the rheological changes. (C) 2002 Elsevier Science Ltd. All rights reserved.