Starch-containing flame retardant PLA system
Starch is polymerized by glucose molecules and stored in cells in the form of starch granules. Starch is a polyhydroxy substance that can be cross-linked into charcoal when burned. It is degradable, renewable, and low-cost, and is considered a promising sustainable material.
Its thermal degradation can be roughly divided into the following three stages: ·
*Physical dehydration mainly occurs. When the temperature reaches about 150 ℃, the crystal water in the starch disappears completely; ·
*Starch thermal decomposition and chemical dehydration occur at about 300 ℃. On the one hand, the condensation reaction between hydroxyl groups forms ether bonds and dehydration; Continuous heating, the molecular chain is broken, forming a variety of aromatic structures; ·
*Carbonization occurs at 500 °C and large aromatic conjugated rings are formed. In the flame retardant PLA system, it can act as a carbon source, releasing carbon dioxide and carbon monoxide during combustion. When compounded 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 thermal oxygen. .
The effective bio-based flame retardant prepared by using renewable and inexpensive potato starch as a bio-based char-forming agent not only promotes the development of green flame retardants, but also greatly reduces the cost of flame retardants. Valuable practical use value.
In addition to the above, bisphenolic acid and other bio-based flame retardants such as protein, tannic acid, itaconic acid, etc. have also been used to flame retardant PLA.
As an important variety of bio-based polymers, using bio-based flame retardants to flame retardant PLA is a necessary way to maintain its green, environmentally friendly and sustainable characteristics. On the existing basis, the future research on bio-based flame retardants will also develop in the direction of high performance, diversification, multifunctionality and low cost.
