New strategies for the construction of eggshell powder reinforced starch based fire hazard suppression biomaterials with tailorable thermal, mechanical and oxygen barrier properties.

A novel eco-friendly approach is highlighted for synthesizing chicken eggshell powder (EP) modified starch-g-poly(N-isopropylacrylamide) (starch-g-PNIPAAm) bionanocomposites (BNCs) by emulsifier-free emulsion polymerisation and aiming to study the effect of EP on the properties of modified starch BNCs. Young's modulus and tensile strength of BNCs are found to be improved dramatically. The enhanced char forming ability of EP improves the thermal stability of BNCs at high temperature as investigated by thermogravimetric analyses carried out in inert atmosphere. The cone calorimeter test revealed that the 4% w/v EP-based BNC resulted suppression on fire hazards in terms of reduction in PHRR (decreased by 33.3%), PSPR (decreased by 75.3%) compared with those of the control starch-g-PNIPAAm and could be attributed to the insulating barrier effect of EP. In addition, the fire retardancy of the BNCs is investigated from limiting oxygen index (LOI) test. The surface morphology and the elemental content of the collected char residues of BNCs after fire retardant test is analysed by FESEM and EDX. Further the oxygen barrier property of BNC with 4% w/v EP is reduced by 73% compared to starch-g-PNIPAAm. The resulting nanostructure and molecular interactions in the BNCs are analysed by FTIR, XRD and TEM.