Lignin is a highly abundant bio-polymeric material that constitutes cellulose one of major component in cell wall of woody plants. Alternatively, large quantity of lignin is yearly available from numerous pulping and paper industries; this is the key point that justifies its large use for industrial applications. Lignin could be one of the most essential and sustainable bio-resources as raw material for the development of environmentally friendly polymer composite. Owing to its huge chemical structure, lignin can provide additional functionality such as filler, reinforcing agent, compatibilizer, stabilizer, etc. In this study, the fire retardant functionality of lignin has been employed in polymeric materials. Due to high charring capability, lignin is effectively used as carbon source in combination with other flame retardants for designing the intumescent system for polymeric materials. Further in this, several articles related to lignin-based intumescent are reviewed and interesting work formulation as well as meaningful results achieved in the flame retardancy are discussed. More attention is given to the studies concerning the use of current intumescent systems for textile applications by means of coating on fabric/nonwoven and melt blending in bulk polymers.
This
study investigates the influence of various lignins and their
content on the thermal stability and fire retardancy of biobased polyamide
11 (PA). Microcomposites based on PA and containing 5, 10, 15, and
20 wt % different lignins were prepared with a twin-screw extruder.
Morphological analysis showed good interfacial interaction and uniform
distribution of lignin particles within the resulting microcomposites.
Further, thermogravimetric analyses carried out in inert atmosphere
indicated that, unlike kraft lignin, which is able to give rise to
the formation of lower char residue (41–48 wt % at 600 °C),
the sulfonated counterpart provides a higher thermal stability as
well as a higher char residue (55–58 wt %). Furthermore, vertical
flame spread tests clearly showed that 15 wt % is the optimum of kraft
or sulfonated lignin loading to achieve improved flame retardant properties
and a V1 rating. In addition, a cone calorimeter was exploited to
study forced combustion behavior; in particular the microcomposites
containing sulfonated lignin revealed significant reductions of the
peak of the heat release rate (−51%) and of the total heat
release (−23%) and a lower average mass loss rate together
with a noticeable increase of the final residual mass (about 9 wt
%). Conversely, the microcomposites containing kraft lignins showed
opposite effect, since heat release rate (HRR) and total heat release
(THR) values increased in the presence of kraft lignin.
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