Flame-retardant plant thermoplastics directly prepared by single ionic liquid substitution

Abstract

Grass and wood biomass (bagasse, cedar, and eucalyptus) was directly converted into flame-retardant thermoplastics by dissolution in an ionic liquid mixture and successive precipitation. During dissolution, the hydroxy groups of the biomass were substituted with a phosphonate-type ionic liquid. The three resulting biomass samples were formed into thin films by hot pressing at 140–160 °C. They also self-extinguished a fire by forming foamed char layers after contacting the fire in an alcohol lamp. In this method, more than 86% of the hydroxy groups were maintained after ionic liquid substitution because the single phosphonate-type ionic liquid acted as a plasticizer and flame retardant in the plant biomass. Therefore, plant biomass-derived flame-retardant thermoplastics have the potential for further functionalization. We developed flame-retardant thermoplastics directly from biomass just by dissolution into ionic liquids and precipitation. During the dissolution, a phosphonate-type ionic liquid adducted on the polymers included in biomass such as cellulose through reaction of the hydroxyl groups. In this method, more than 86% of the hydroxy groups were maintained after ionic liquid substitution because the single phosphonate-type ionic liquid acted as a plasticizer and flame retardant in the plant biomass. Therefore, the plant biomass-derived flame-retardant thermoplastics have the potential for further functionalization.