A phosphorus-nitrogen containing dendrimer reduces the flammability of nanostructured polymers with embedded self-assembled gel networks

A novel phosphorus-nitrogen containing dendrimer DPC-PAMAM has been obtained by the functionalization of amine terminated poly(amidoamine) (PAMAM) with diphenyl phosphoryl chloride (DPC), which is used to modify polyurethane (PU) as an intumescent flame retardant. The gel-phase network, made up of a number of nanofibers, is formed by the self-assembly of DPC-PAMAM dendrimer, which is embedded in the PU matrix by in situ polymerization. The results from thermogravimetric analysis (TGA) and cone calorimeter testing indicate that the addition of the DPC-PAMAM gelator improves thermal stability and reduces significantly the flammability (including peak heat release rate (PHRR), total heat release (THR), average mass loss rate (AMLR), etc.) of PU resin. Furthermore, incorporating the DPC-PAMAM gelator into the polymer matrix enhances the strength of PU resin. The scanning electron microscopy (SEM) images show that a compact and dense intumescent char is formed for PU composites filled with DPC-PAMAM after combustion, which results in the improvement of flame-retardant properties of the polymer matrix by condensed phase flame retardancy.