Preparation of flame retardant polyurethane foam reinforced with modified cellulose.

Abstract

Expandable graphite (EG) is a flame-retardant material that is useful for polyurethane foam (PUF) synthesis. However, it shows the disadvantage of reducing mechanical strength, which limits its field of application. In this study, to overcome the limitations of EG/PUF composites, cellulose-based flame retardants as a reinforcement were prepared using a novel method. Microcrystalline cellulose (MCC) was grinded to a suitable size to be appling as a reinforcement for urethane foam. The ground MCC was coated with the mussel-derived adhesive protein, dopamine, and formed an 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. Ground MCC-based flame retardant (GCF) was incorporated into the EG/PUF composites. The PUF mixed with 3 wt% of GCF and 12 wt% of EG was found to have an excellent limiting oxygen index of 25.3%, while the LOI of pure PUF was 19.3%. In particular, the compressive strength of GCF3 was remarkably enhanced compared with the PUF containing 15 wt% of EG. This provides a simple and comprehensive solution for PUF applications requiring high flame retardancy and mechanical strength.