Since the rapid development of bio-based materials, the research of supporting bio-based additives has also been put on the agenda. In fact, the use of bio-based raw materials to prepare additives has already existed. At present, many lubricants, plasticizers, and antioxidants are prepared from bio-based raw materials. With the improvement of safety requirements during the use of materials, the flame retardant properties of bio-based materials have also become their must-have properties. Therefore, research on bio-based flame retardants has emerged.
The reason why bio-based materials can be used as raw materials for flame retardants is that many bio-based materials have high carbon content and a polyhydroxyl structure, so they have excellent char-forming properties. Char-forming properties are the most important of intumescent flame retardants. Mechanism of action, the flame retardant effect of intumescent flame retardants mainly relies on the formation of a porous foamed coke layer on the surface of the material. It is a multi-phase system containing solid and liquid and gaseous products. The flame-retardant properties of the carbon layer are mainly reflected in: making it difficult for heat to penetrate the condensed phase, preventing oxygen from entering the combustion zone, and preventing gaseous or liquid products generated by degradation from overflowing the surface of the material. The formation process of the coke layer is: at about 150°C, the acid source produces an acid that can esterify polyols and can be used as a dehydrating agent; at a slightly higher temperature, the acid and the carbon source undergo an esterification reaction, while the amine groups in the system are As a catalyst for the esterification reaction, it accelerates the reaction; the system melts before and during the esterification reaction, and the incombustible gas generated during the reaction makes the system in the molten state expand and foam, and at the same time, the polyol and ester are dehydrated After carbonization, inorganic substances and carbon residues are formed, and the system is further foamed; when the reaction is close to completion, the system gels and solidifies, and finally a porous foamed carbon layer is formed.
PLA is flammable and is accompanied by severe dripping, which limits its application in electronic appliances, automobiles and other fields that require high flame retardant performance. Adding flame retardants to PLA is a simple and efficient flame retardant method. Considering that PLA itself is a bio-based polymer, it is also necessary to consider whether the addition of flame retardants will destroy its bio-based properties. At present, there have been a large number of research reports on using halogen-free flame retardants to improve the flame retardancy of PLA. In order to improve the flammability of PLA while maintaining its bio-based characteristics, people try to compound bio-based materials with existing flame retardants, or use bio-based materials as raw materials to give it as a flame retardant through physical or chemical methods. Characteristics, this is also a hot spot in the research of flame-retardant PLA.
