Manufacturing Greener Fire Retardants by Incorporating Bio-Based Materials into Intumescent Flame Retardant Polypropylene Composites

Abstract

Synthetic plastics are seemingly everywhere and are easily the class of materials which defines the current area of human history, like stone or bronze before them. Synthetic polymers tend to ignite easily and burn intensely, sometimes producing toxic fumes as they burn. This makes the development of flame retardants for synthetic polymers imperative. The concept of intumescent flame retardants is not new but has received increased attention as the historically preferred halogenated flame retardants are phased out. The required components of intumescent flame retardant systems lend themselves very well to substitutions by various types of biomass and other naturally-occurring molecules, leading to greener flame retardant materials.

The objective of this research is to imbue polypropylene composites with sufficient flame retardancy by including one of two bio-based materials in intumescent flame retardant composites: lignin or phytic acid. Fire testing on the lignin-containing composites showed only marginal improvements in fire retardancy. The phytic acid-containing composites exhibited very promising behavior, with substantially lower peak heat release rates and formation of stable chars. In addition, the inclusion of metal-organic framework synergists was shown to further improve the flame retardancy of the polypropylene/phytic acid composites.