Core-shell flame retardants based on Chitosan@MMT coated ammonia polyphosphate for enhancing flame retardancy of polyurethane

In this manuscript, the core-shell flame retardants based on chitosan@MMT coated ammonia polyphosphate (APP@CS@MMT) was prepared and then incorporated into the TPU matrix. Through analyzing the effects of the flame retardant on the property reinforcements, it's found that TPU/APP@CS@MMT composites have the excellent flame retardant and smoke suppression performance. The pHRR, THR, pSPR and TSP of TPU/ APP@CS@MMT composites were remarkably decreased by 62.58%, 71.56%, 90.43%, 83.22%, and 93.60%, respectively. Furthermore, the mass of residual chars increased significantly from 0.85% for pure TPU to 21.95% for TPU/APP@CS@MMT composites. The TPU/APP@CS@MMT composites can improve both the flame-retardant and smoke suppression performances of TPU. Through the thermogravimetric test, cone calorimetry test, and char structure analysis, the flame retardant mechanism of the TPU/ APP@CS@MMT composites was also investigated. The APP@CS@MMT mainly plays its flame retardant role in the condensed phase. This work also provides a green and facile methodology for creating flame retardant TPU and helps broaden the TPU's practical application in industry.