Purification effect of pyrolyzed filler on the flammability of polylactide matrix

Abstract Research efforts are underway around the world to develop efficient recycling of the continuous phase of polymer composites toward reuse. It has already been demonstrated that pyrolyzed filler (PF) can be successfully used as a flame retardant for synthetic polyesters, including recycled ones. Therefore, the purpose of this work was to test the effect of PF on the flammability and thermal properties of the biopolyester phase. For this purpose, the pyrolysis technique was used, which yields a valuable solid phase in addition to the gas and liquid phases. To effectively give it a second life, a proprietary method of modifying the filler recovered by pyrolysis was developed to effectively separate and remove an organic part in the form of a layer of amorphous carbon (a-C), which acts as a universal sorbent. For this purpose, the a-C phase was extracted using binary solvent and replaced it using three types of salts: ammonium salt of benzyl phosphite, 1-butyl-3-methylimidazolium chloride (BMIC), and methyldodecylbenzyl trimethyl ammonium chloride (BMAC). Using a high-temperature processing technique, polylactide composites containing 5% (by weight) additive were obtained. The results of thermal (TGA, DSC) and flammability (PCFC, UL94, LOI) analysis studies show that the use of BMIC and BMAC salts for the intended purpose is particularly promising. The thermal stability of PLA composites containing SF-BMIC and SF-BMAC increased by 30 K and the flammability decreased by 23%. These promising results have opened up new avenues of research toward the synthesis of bio-flame retardants dedicated specifically to polylactide. Graphical abstract