Kraft Lignin Bio-Polymer for Polyurethane Foams is the right alternative for a probable partial replacement of both the Polyol and diisocyanate
expandable graphite
Expandable Graphite in Polyurethane Foams
Expandable Graphite an intercalation compound used in Polyurethane Foams to make PU foams durable & less flammable with less wetting property
