Starch is composed of amylose and amylopectin. It has the advantages of being degradable, renewable, and low-cost. It is considered a promising sustainable material. The thermal degradation can be roughly divided into the following three stages: (1) Physical dehydration mainly occurs, when the temperature reaches about 150 ℃, the crystal water in the starch completely disappears; (2) Starch thermal decomposition and chemical dehydration occur at about 300 ℃ On the one hand, the condensation reaction between the hydroxyl groups forms ether bonds and dehydration. On the other hand, the adjacent hydroxyl groups in the glucose ring will also be chemically dehydrated to form carbon-carbon double bonds or ring breaks. When the temperature continues to rise, the molecular chain breaks and forms a variety of aromatics. Structure; (3) Carbonization reaction occurs at 500 ℃ and a large aromatic conjugated ring is formed.
Starch can act as a carbon source in the flame-retardant PLA system. It will release carbon dioxide and carbon monoxide during combustion. When combined with an acid source, the acid source can promote the dehydration and carbonization of starch, and the formed carbon layer can inhibit the escape of combustible gas and the exchange of heat and oxygen.
Flame retardant PLA with other bio-based flame retardants，like bisphenolic acid and other bio-based flame retardants such as protein, tannic acid, itaconic acid.
