Many polymeric materials, e.g. polypropylene and polystyrene, commonly used for a plethora of different applications are considered problematic due to their increased flammability as well as the release of toxic gases and smoke during combustion. Thus, the fire-resistance of these materials needs to be increased which is nowadays typically achieved by incorporation of halogenated additives acting as flame retardants.^[1]
However, these flame retardants are known to be a source of environmental pollution. As low molecular weight compounds, the halogenated additives are able to migrate from the polymeric matrix into the environment leading to measurable concentrations in, e.g., house dust^[2] or urban air^[3]. Interestingly, the criteria which have to be met in order to be suitable as a flame retardant such as long term stability and non-polar structure also classify these additives as organic pollutants due to, e.g., persistence and accumulation in the lipid tissue of animals.^[4]
Additionally, halogenated flame retardants release corrosive and hazardous hydrogen halides during combustion because of their mode of action.
In the search for less toxicologically harmful and more environmentally friendly flame retardant solutions, organisms and biological structures which have evolutionarily adapted to fire-prone habitats are considered promising candidates for the development of biogenic and bioinspired compounds. In this regard, first investigations of Vespula germanica nests, which are built of a paper-like composite of wood particles and protein-rich saliva, showed low flammability as well as good structural integrity of the residual material compared to synthetic papers.
Thus, possible agents, structures and mechanisms retarding the combustion of wasp nests were investigated and synthetical polymer-based materials mimicking the composite used for nest building were developed. The wood polymer composites were prepared by extrusion, tested for their flammability and analyzed by light-microscopy as well as scanning electron microscopy before and after combustion.



References
[1]    F. Laoutid, L. Bonnaud, M. Alexandre, J.-M. Lopez-Cuesta, P. Dubois, Mater. Sci. Eng. R Rep. 2009, 63, 100.
[2]    N. Ali, S. Harrad, E. Goosey, H. Neels, A. Covaci, Chemosphere 2011, 83, 1360.
[3]    A. Salamova, M. H. Hermanson, R. A. Hites, Environ. Sci. Technol. 2014, 48, 6133.
[4]    X. Zhang, R. Sühring, D. Serodio, M. Bonnell, N. Sundin, M. L. Diamond, Chemosphere 2016, 144, 2401.