Biochars can be highly porous (high surface area), giving mechanical performance and compatibility advantages in polymers (infiltration of pores by polymer), and are fire resistant. Low grade wool is a widely available waste fibre with good charring ability.
Both can therefore be attractive renewable components for polymer composites. In this paper, a composite with 15% pine wood sawdust biochar (pyrolysis at 500°C followed by activation at 900°C), 10% wool fibres and 15% ammonium polyphosphate (PIN flame retardant) in polypropylene was tested for fire performance and mechanical properties. This composite showed fire performance with reduced peak heat release rate (PHRR), reduced smoke production and lower carbon monoxide emission, enhanced LOI (limiting oxygen index) and mechanical properties comparable to or better than pure polypropylene (flexural strength, tensile/flexural moduli).
“Development of waste based biochar/wool hybrid biocomposites: Flammability characteristics and mechanical properties”, O. Das, Journal of Cleaner Production 2017 http://dx.doi.org/10.1016/j.jclepro.2016.12.155