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Synergistic combinations of phosphonates with other flame retardants in thermoplastic elastomers

von Dr. Xiudong Sun, Dr. Jan-Pleun Lens, Dr. Zhiyuan Lan,

Thermoplastic polyurethane (TPU) and copolyester thermoplastic elastomers (TPE-E) are among the engineering thermoplastic elastomers (TPEs) used in wire and cable applications due to their processing advantage of being thermoplastics and having the flexible and low modulus properties of elastomers. A number of non-halogenated flame retardant systems have been used in these applications but a relatively high loading typically leads to poor mechanical properties such as high modulus or low elongation at break as well as a rough surface appearance. Also, high levels of non-melting flame retardant additives leave less room for functional fillers (e. g. conductive) in the formulations. The present work shows the surprisingly better flame retardant performance and improved mechanical properties of flame retardant TPU and TPE-E when melt processable polyphosphonates and phosphonate oligomers are combined with these non-melting flame retardants. The effects are truly ­synergistic because the improved properties are obtained at an even lower total amount of flame retardants (and thus lower cost) than when these flame retardants are used by ­themselves. The hydrolytic and thermal stability of these new systems have also been demonstrated.