Flame retardancy mechanisms of metal phosphinates and metal phosphinates in combination with melamine cyanurate in glass-fiber reinforced poly(1,4-butylene terephthalate): the influence of metal cation
Ulrike Braun
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
Search for more papers by this authorHorst Bahr
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
Search for more papers by this authorHeinz Sturm
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
Search for more papers by this authorCorresponding Author
Bernhard Schartel
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany.Search for more papers by this authorUlrike Braun
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
Search for more papers by this authorHorst Bahr
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
Search for more papers by this authorHeinz Sturm
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
Search for more papers by this authorCorresponding Author
Bernhard Schartel
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany.Search for more papers by this authorAbstract
The pyrolysis and fire behavior of glass-fiber reinforced poly(butylene terephthalate) (PBT/GF) with two different metal phosphinates as flame retardants in combination with and without melamine cyanurate (MC) were analyzed by means of thermogravimetry, thermogravimetry coupled with infrared spectroscopy, flammability, and cone calorimeter tests as well as scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray fluorescence spectroscopy. In PBT/GF, dosages of 13–20% of the halogen-free flame retardant aluminum phosphinate or aluminum phosphinate in combination with MC fulfill the requirements for electrical engineering and electronics applications (UL 94 = V-0; LOI > 42%), whereas the use of the same amount of zinc phosphinate or zinc phosphinate in combination with MC does not improve the fire behavior satisfactorily (UL 94 = HB; LOI = 27–28%). The performance under forced flaming conditions (cone calorimeter) is quite similar for both of the metal phosphinates. The use of aluminum and zinc salts results in similar flame inhibition predominantly due to the release of the phosphinate compounds in the gas phase. Both metal phosphinates and MC interact with the polymer changing the decomposition characteristics. However, part of the zinc phosphinate vaporizes as a complete molecule. Because of the different decomposition behavior of the metal salts, only the aluminum phosphinate results in a small amount of thermally stable carbonaceous char. In particular, the aluminum phosphinate-terephthalate formed is more stable than the zinc phosphinate-terephthalate. The small amount of char has a crucial effect on the thermal properties and mechanical stability of the residue and thus the flammability. Copyright © 2008 John Wiley & Sons, Ltd.
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