Flame Retardant PLA System Containing Phytic Acid
Phytic acid (PA) is composed of 6 phosphoric acid groups and contains up to 28% of P. It is mainly stored in seeds such as oils and cereals. It is a natural plant acid. From the perspective of flame retardant, the higher the phosphorus content of the flame retardant, the better the flame retardant performance.
chemical structure of phytic acid
In addition, PA also has the advantages of non-toxic, renewable and degradable, and 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 thermally decomposed, it will generate acid substances such as metaphosphoric acid, which can be used as a dehydrating agent to catalyze the dehydration and carbonization of the carbon source, and 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 suppressing the formation of volatile substances in the gas phase, and preventing further combustion of the fabric.
Different metal phytates (Na-Phyt, Fe-Phyt, Al-Phyt) were added to PLA, and the composites were prepared by melt blending. Compared with pure PLA, the RPHRR of PLA/20 % Al-Phyt decreased the most. As high as 44%, the HTHR was reduced by 20%, indicating that Al-Phyt could significantly improve the combustion performance of PLA, but the addition of Al-Phyt would lead to thermal degradation of PLA during processing.
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
