Dynamic mechanical and thermal properties of fire‐retardant polypropylene

A study of the effect of a series of fire retardants and antimony oxide upon the dynamic mechanical and thermal properties of polypropylene suggests three categories. (1) “Inert Fillers”—These raise the elastis modulus and the heat distortion temperature of polypropylene without shifting its glass transition temperature. The melting point of polypropylene is only depressed by 1–3°C, the heat of fusion and the percentage of crystallinity of polypropylene in these composites is ∼10 percent lower at additive concentrations of ∼30 percent. Very poor interaction exists between the additive and the thermo‐plastic which apparently exist in two separate phases. (2) “Chain Stiffener”—These raise the elastic modulus (∼25 percent) and the glass transition (∼11°C) for polypropylene; the melting point of polypropylene in the composite is lowered by ∼6°C indicative of good interaction between the additive and polypropylene. (3) “Plasticizer”—These lower the room temperature elastic modulus (∼20 percent) and the glass transition temperature (∼11°C) of polypropylene; the melting point of polypropylene in the composite is depressed by ∼10°C indicating good interaction. The efficacy of the “plasticizer” and “chain stiffener” are attributed partially to melting of polypropylene at the processing temperature.