Preparation of a reactive flame retardant by functional modification of lignin and its application in phenolic foam

Abstract

With the emergence of new standards for fire prevention, phenolic foam has attracted increasing attention due to its satisfactory cleanliness and flame retardancy. With the increasing exhaustion of fossil energy and environmental problems, finding renewable energy sources to replace petroleum-derived phenol has become a new research hotspot. Lignin is an ideal renewable resource, which can be used to partially replace phenol in phenolic foam due to its structural similarity to petroleum phenolic compounds. In this paper, lignin sulfate was used as a raw material, an aldehyde group was introduced from an external source, and on this basis, nitrogen and phosphorus modification was carried out to prepare lignin-based flame retardants, which were used to replace phenol in the production of phenolic foam. The nitrogen and phosphorus modification was conducted to prepare the lignin-based flame retardants. It was found that when the amount of flame retardant replaced was 5–20%, the compressive strength of the modified phenolic foam was better than that of pure phenolic foam. The LOI of the modified phenolic foam also improved significantly (to about 59.6%). In addition, the heat release rate, total heat release and total smoke release of the modified phenolic foam decreased obviously. This paper provides an effective method for lignin utilization to prepare bio-based phenolic foams with improved flame retardancy and mechanical properties.