Flame retardant and mechanical properties of expandable graphite/polyurethane foam composites containing iron phosphonate dopamine-coated cellulose

Abstract

Additive-type flame retardants used in polyurethane foams (PUFs) have low compatibility with the matrix and have a large particle size which reduces the mechanical strength. To overcome this, cellulose-based additive-type flame retardants were prepared. Microcrystalline cellulose (MCC) was grinded to a suitable size to be applying as a reinforcement for urethane foam. The ground MCC was coated with the mussel-derived adhesive protein, dopamine, and formed the iron phosphonate coordination network on the surface. It was confirmed that the modification proceeded well by structural analysis by Fourier-transform infrared spectrometer and morphology analysis by scanning electron microscope. In the synthesis of PUF, expandable graphite (EG) was added to obtain high flame retardancy. The PUF mixed with 3 wt% of ground MCC-based flame retardant and 12 wt% of EG (GCF3) was found to have an excellent limiting oxygen index (LOI) of 25.3%, while the LOI of pure PUF was 19.3%. In particular, the compressive strength of GCF3 was remarkably enhanced (21 wt%) compared with the PUF containing 15 wt% of EG. This study produced a new additive-type flame retardant to improve mechanical strength. This provides a simple and comprehensive solution for PUF applications requiring high flame retardancy and mechanical strength.