PHOENIX - Bio-Based Flame Retardants for Plastics

Adding Value to Biomass Through Chemical Modification

Lignin is a natural material produced in large quantities for which there is currently little significant material utilization. It is a major component of woody plants and remains as a by-product of paper manufacturing. Today, more than 98 percent of lignin is burned to meet the energy demands of paper mills. 

Numerous research activities are focused on using lignin in plastic applications, either as a partial substitute for petroleum-based polymers or as a means of introducing additional functionality. One well-known property of lignin as a polymer additive is its ability to reduce the flammability of plastics. This effect can be enhanced through the simultaneous presence of phosphorus-containing compounds. However, this finding has not yet been widely exploited in technical applications because the flame-retardant effect is often insufficient. Furthermore, due to its incompatibility with many polymer systems, adding lignin can reduce the mechanical performance of plastics.

Lignin as a Flame Retardant for Industrial Applications

One reason for the limited flame-retardant performance of lignin combined with phosphorus-containing compounds is that both components are typically dispersed separately within the polymer matrix. This spatial separation prevents them from acting synergistically. Fraunhofer LBF addressed this challenge by chemically bonding phosphorus directly to the lignin. The modification process was specifically designed with future industrial-scale implementation in mind. Following successful development at laboratory scale, the synthesis of phosphorylated lignin was carried out in Fraunhofer LBF’s in-house kilo laboratory. Larger quantities of the material were then provided to project partners for processing with various plastic systems. 

Fire testing conducted at the University of Lille using a mass-loss calorimeter demonstrated lower heat release rates for plastics containing phosphorylated lignin developed by Fraunhofer LBF compared with materials containing unmodified lignin. Morphological investigations of polypropylene compounds containing either untreated or phosphorylated lignin showed that, due to incompatibility effects, untreated lignin formed large and unevenly distributed agglomerates, resulting in reduced tensile strength. Additional chemical modification through hydrophobization improved the compatibility of lignin with polypropylene. This enhancement was reflected in a finer material morphology and improved mechanical properties. 

Comfortable, durable, bio-based - a foam for many industries

For foam processors, furniture manufacturers, and seating manufacturers, it is particularly important that “OrganoFoam” can be integrated into existing production processes without major changes. Tests conducted at Friedrich Platt GmbH show that the supplied blocks can be easily cut to size using existing systems, bonded together to form larger surfaces, and laminated with standard upholstery fabrics. As part of the project, a demonstration sofa was created to test seating comfort and long-term durability under real-world conditions.

“OrganoFoam” is suitable for manufacturers who want to strengthen their brands with credibly sustainable lines of furniture, seating, and mattresses. The high proportion of biogenic carbon and improved UV resistance contribute to a positive carbon footprint and a long service life. In the future, additional applications are conceivable, such as in medical positioning aids, acoustic damping elements, or shock-absorbing packaging, where soft, durable, and sustainable foams are in demand.

Funding and Partners

The PHOENIX project received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. 310187