The chemical structure of phytic acid (PA) is shown in Figure 6. It is composed of 6 phosphoric acid groups and contains up to 28% P. It is mainly stored in seeds such as oils and cereals. It is a natural plant acid. From a flame retardant point of view, the higher the phosphorus content of the flame retardant, the better the flame retardant performance. In addition, PA also has the advantages of non-toxic, renewable and degradable. It is a green flame retardant with high potential. Under nitrogen atmosphere, PA will undergo dehydration, thermal decomposition and carbonization during the heating process, and the carbon residue rate is high. , Can be used for flame retardant PLA. PA is usually used as the acid source in the intumescent flame retardant system. When it is decomposed by heat, it will generate acidic substances such as metaphosphoric acid. It can be used as a dehydrating agent to catalyze the dehydration and carbonization of the carbon source to further improve the flame retardant performance of the system.
This is due to the high phosphorus content of PA, which promotes the formation of a carbon layer during combustion, thereby reducing heat transfer efficiency, effectively inhibiting the generation of volatile substances in the gas phase, and preventing further combustion of the fabric. Different metal phytates (Na-Phyt, Fe-Phyt, Al-Phyt) are added to PLA, and composite materials are prepared by melt blending. Compared with pure PLA, the RPHRR of PLA/20% Al-Phyt is reduced the most As high as 44%, HTHR is reduced by 20%, indicating that Al-Phyt can significantly improve the combustion performance of PLA, but the addition of Al-Phyt will cause thermal degradation of PLA during processing. For the first time, Feng et al. used the green electrochemical method to modify the surface of graphene by using PA to prepare iron phytate functionalized graphene (f-GNS) and added it to PLA. They found that the synergistic mechanism of f-GNS makes the material excellent Flame retardant performance. Compared with pure PLA, when the content is only 3.0%, the RPHRR and HTHR of PLA/f-GNS nanocomposites are reduced by 40% and 16%, respectively.
PA can also be compounded with bio-based polymers to prepare fully bio-based flame retardants with excellent flame retardant properties. High phosphorus content is the advantage of PA flame-retardant PLA, but PA is expensive, and it is not suitable for large-scale use in industry from the perspective of cost.
