Since the rapid development of bio-based materials, the research on matching bio-based additives has also been put on the agenda. The use of bio-based raw materials to prepare auxiliaries has actually existed for a long time. 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 performance of bio-based materials has also become a must-have performance, so the research on bio-based flame retardants has emerged as the times require.
The flame retardant principle of flame retardants
The combustion reaction generally has three elements: combustibles, oxygen and a certain temperature, and one of them is indispensable. The mechanism of action of flame retardants should inhibit the production of one or more elements when the material burns, so as to prevent or slow down the burning.
The specific flame retardant mechanism of each flame retardant is different, but the basic principle of flame retardant is roughly the same. It reduces the generation of flammable gas during thermal decomposition and hinders the basic reaction in the gas combustion process, and absorbs in the combustion domain. The heat, diluting and isolating the air, also plays a role in preventing combustion.
According to the application mode, flame retardants can be divided into additive flame retardants and reactive flame retardants. Additive flame retardants are directly mixed with resins or rubber compounds, which are easy to process and have a wide range of adaptability. They are the main body of flame retardants; reactive flame retardants are often bonded to the polymer chain as monomers, which have little impact on product performance. And the flame retardant effect is lasting.
Bio-based flame retardants are mainly intumescent flame retardants. The flame retardant principle of intumescent flame retardants relies on the formation of a porous foamed coke layer on the surface of the material. It is a multiphase system containing solid and liquid and gaseous products.
At lower temperatures, the non-bicyclic phosphorus in the compound produces phosphoric acid that can act as a dehydrating agent; the water vapor generated by the reaction and the non-flammable gas generated by the gas source expand and foam the molten system.
At the same time, the polyol is dehydrated and carbonized to form inorganic substances and carbon residues, and the system is further expanded and foamed; when the reaction is nearly completed, the system gels and solidifies, and finally forms a porous foam carbon layer, which prevents heat transfer and reduces flammable gases. release and oxygen isolation to achieve the purpose of flame retardant.
PLA is flammable and accompanied by severe dripping, which limits its application in electronic appliances, automobiles and other fields that require high flame retardant properties. Adding flame retardants to PLA is a simple and efficient way to flame retardant. 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.
In order to improve the flammability of PLA while maintaining its bio-based properties, people have tried 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. characteristic.
