Thermal Stability and Fire Properties of Salen and Metallosalens as Fire Retardants in Thermoplastic Polyurethane (TPU)

This study deals with the synthesis and evaluation of salen based derivatives as fire retardants in thermoplastic polyurethane. Salens, hydroxysalens and their first row transition metal complexes (salen-M) were synthesized (Copper, Manganese, Nickel and Zinc). They were then incorporated in thermoplastic polyurethane (TPU) with a loading as low as 10:1 weight ratio. The thermal stability as well as the fire properties of the formulations were evaluated. Thermogravimetric analysis (TGA) showed that different coordination metals on the salen could induce different decomposition pathways when mixed with TPU. The Pyrolysis Combustion Flow Calorimetry (PCFC) results showed that some M-salen have the ability to significantly decrease the peak heat release rate (−61% compared to neat TPU) and total heat released (−63% compared to neat TPU) when formulated at 10:1 wt % ratio in TPU. Mass Loss Cone Calorimetry (MLC) results have shown that some additives (salen-Cu and salen-Mn) exhibit very promising performance and they are good candidates as flame-retardants for TPU.