Zinc hydroxystannate

The performance of aluminium hydroxide/magnesium hydroxide-filled systems can be enhanced by incorporation of zinc hydroxystannate in halogen-free rubbers giving reduced smoke and toxic gas emission, coupled with higher flame retardancy. This action will be complimentary to the water release and endothermic effects of aluminium hydroxide/magnesium hydroxide filler systems. 

In halogen-containing rubbers, zinc hydroxystannate can be substituted as a non toxic replacement for antimony trioxide to reduce smoke and toxic gas emission. Zinc hydroxystannate does not pigment the rubber and can be used to produce clear or translucent products. 

Zinc hydroxystannate and zinc stannate were synthesised at I.T.R.I. according to previously reported procedures (11,12)... 

Antimony trioxide, 8-stannic acid (hydrous tin(IV) oxide), zinc hydroxystannate, and zinc stannate were incorporated into the commercial brominated polyester resin at levels of 1,2,5 and 10% by weight. No processing problems were encountered and the samples cured satisfactorily to give rigid, opaque strips. 

Simultaneous TG/DTA studies of zinc hydroxystannate (Figure 6), indicate that dehydration of this compound occurs during the temperature range 190°-285°C, with a loss of 19.1% of its initial weight, this corresponding to the loss of 3 moles of water ... 

Zinc hydroxystannate and zinc stannate are very effective flame-retardant synergists when incorporated at levels of 1-10% into... 

Inorganic tin compounds, in particular, zinc hydroxystannate and zinc stannate, are effective fire retardants in a number of polymer systems. They appear to have advantages over certain existing commercial additives, namely ... 

Baggaley, R.G., Hornsby, P.R., Yahya, R., Cusack, P.A., and Monk, A.W., The influence of novel zinc hydroxystannate-coated fillers on the fire properties of flexible PVC, Fire Mater., 21, 179, 1997. 

Cusack, P.A. and Hornsby, P.R., Zinc hydroxystannate/zinc stannate-coated fillers Novel flame retardants and smoke suppressants for polymeric materials, J. Vinyl Additive Technol., 5, 21-30, 1999. 

Hornsby, P. R., Cusack, P. A., Cross, M., Toth, A., Zelei, B., and Marosi, G. 2003. Zinc hydroxystannate-coated metal hydroxide fire retardants Fire performance and substrate-coating interactions. Journal of Materials Science 38 2893-99. 

Zinc borate is also an effective SS in combination with phosphate ester plasticiser (130). The combination of ammonium octamolybdate and zinc stannate is also beneficial (435). It has been shown that ATH and MDH functional fillers coated with zinc hydroxystannate give significantly increased combustion resistance and lower levels of smoke evolution (386). Copper (I) complexes have been suggested as smoke suppressants (241). Copper oxides have also been investigated with positive results (60). 

The increasing demand for FR PVC-U applications has prompted work in this area. The use of functional fillers can cause a dramatic deterioration of physical properties at the addition levels necessary to achieve the requirements of flame retardancy and smoke emission. An evaluation has shown zinc hydroxystannate to give the best overall FR and SS characteristics without adversely influencing important physical properties (129). The addition of low levels of zinc borate and/or ATH was noted to improve flame retardancy and reduce smoke density in a PVC-U formulation (265). 

An investigation was carried out into the fire retardant behaviour of zinc hydroxystannate-coated fillers (alumina trihydrate and magnesium hydroxide) in PVC and EVA cable formulations. Measurements were made of the limiting oxygen index, peak rate of heat release and smoke parameter and the data for unfilled and filled formulations compared. X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier-transform spectroscopy were used to study the filler-coating interaction. 16 refs. 

Atlanta, Ga., 26th-30th April 1998, p.3310-2. 012 NOVEL ZINC HYDROXYSTANNATE-COATED FILLERS AS FIRE RETARDANT AND SMOKE SUPPRESSANT ADDITIVES FOR HALOGENATED POLYMERS Hornsby P R Cusack P A... 

Consideration is given to the influence of combinations of zinc hydroxystannate (ZHS) with hydrated fillers, on the fire properties of plasticised PVC and polychloroprene. It is shown that magnesium and aluminium hydroxides specially coated with ZHS, confer significantly increased combustion resistance and lower levels of smoke evolution to these polymers. This permits large reductions to additive loading relative to unmodified filler, without sacrificing flame retardant or smoke suppressant performance. 10 refs. 

By far the most important tin-based fire retardants are the zinc stannates - zinc hydroxystannate (ZHS) and its anhydrous analog, zinc stannate (ZS). Originally developed at ITRI during the mid-1980s, these additives are now being marketed worldwide as non-toxic flame retardants and smoke suppressants for use in a wide range of polymeric materials. ... 

Table 3.5.1 Properties of zinc hydroxystannate and zinc stannate...

Flamtard S (zinc stannate), Flamtard H (zinc hydroxy stannate), Flamtard HB1 (zinc hydroxystannate/zinc borate blend)... 

High efficiency in char formation is one of the reasons for the strong performance of Mg(OH)2 and A1(OH)3 as fire retarding additives. This performance can still be enhanced by surface coating the fillers with zinc hydroxystannate. Sb2O3 is volatized from the material and therefore does not affect char formation. Formation of char is an effective method of increasing the fire resistance of materials. The material which forms carbonaceous char has a reduced ability to supply the gaseous fuels required to fuel the fire. 

Figure 13.8. The effect of a zinc hydroxystannate coating on limiting oxygen index. [Data from Baggaley R G, Hornsby P R, Yahya R, Cussak P A, Monk AW, Fire Mater., 21, 1997, 179-85.]...

Zinc hydroxystannate was found to enhance the performance of Mg(OH)2 and A1(OH)3. Figure 13.8 shows the effect of filler coated with zinc hydroxystannate on... 

Methods of filler pretreatment coating with thermoplastic polymer zinc hydroxystannate coating of fire retardant fillers increases their performance... 

In polyolefins and epoxy resins melamine octamolybdate reduces the smoke development during the process of carbrniization of aromatic compounds. Other known smoke inhibitors are zinc borate, zinc stannate, and zinc hydroxystannate. 

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