Antimony loading levels

A juxtaposition of the data in Fig. 4.9 with the equilibrium phase diagram of the Pb—Sb system presented in Fig. 4.3 indicates that, at 252 °C and up to 3.5 wt% loading level in the alloy, antimony has the highest solubility in a-Pb dendrites. On cooling, the dendrites get oversaturated with Sb and reorganisation of the structure of the solid phases starts, whereby the content of Sb in the a-Pb dendrites diminishes to 0.1% at room temperature. This improves the mechanical properties of the alloys. At Sb content between 3.0 and 11 wt%, the amount of the eutectic phase in the alloys changes but slightly, which results in minor improvement of their mechanical properties. 

To improve the fire retardancy of polypropylene, beyond the UL 94 V-2 level, it is necessary to use blends of aromatic bromine fire retardants with antimony trioxide as a synergist. The usual loading is between 35% and 40% fire retardant however, the additional cost may prohibit commercialization. Moreover, the presence of aromatic bromine increases the photooxidation of polypropylene67 69 inactivating hindered amines. To reduce the cost without losing in efficacy the combination of brominated flame-retardant/antimony trioxide system with magnesium hydroxide... 

CHARMAX LS are zinc-molybdenum complexes targeted as smoke suppressants in PVC wire and cable, PVC plastisols and rigid PVC products. LS Z4A is used in a simple PVC jacket formulation. Aroimd 5% of such additives can replace up to 20% of AOM and reduce the afterglow sometimes seen with antimony oxide containing formulations. Also CHARMAX products are cheaper by weight than primary molybdenum and tin-based additives, AOM and zinc starmate, and lower loadings provide the required level of flame retardancy or smoke suppression that may be specified. The complexes may be used as partial of complete replacements for antimony oxides, whose price and supply has been unpredictable in recent times. 

Chlorinated FRs have been used for many years in combination with antimony oxide in polyethylenes. The optimum FR antimony oxide ratio is 1 1, but the oxide can be minimized by increasing the ratio to 2 1 and even 3 1. For a UL 94 V-0 rating, the amount of additive required depends on the melt index of the polymer high levels being required for higher loadings. 

Antimony oxide in combination with halogenated additives has been used in the plastic industry for many years to flame retard plastics. By blending synergists, such as Ferro-Char, the total flame retardant system loading can be effective at lower levels. 

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