EoW March 2008

216 / 240

EuroWire – March 2008 214
english
Based on these results, it was concluded
that KG-STA demonstrated a far more
efficient use of the AOM chemistry in two
different flexible PVC formulas and at
different use levels.
4.2 Cone Calorimeter
The smoke suppression effectiveness of
KG-STA and the two commercial AOM
samples were further compared using
cone calorimeter testing (ASTM E-1354).
The same two model flexible PVC formulas
(Table 3, shown earlier) were used in this
study. Product comparisons were again
conducted at 5, 10 and 15 phr total AOM
with talc levels adjusted to maintain a
fixed total filler level. All cone calorimeter
testing was conducted at an irradiance of
70 kW/m².
Figures 9 and 10 present the total smoke
generated from combustion of the various
PVC samples as a function of use level.
The results paralleled those obtained
with the NBS smoke chamber. In the
30 phr ATH system, KG-STA far exceeds
the performance of Climax WA 011GA
at all use levels.
The total smoke achieved with 5 phr
KG-STA was virtually the same as that
obtained with Climax WA 011GA at 10
phr. KG-STA also outperformed the best
commercial AOM, Climax A2017I.
In this case, the total smoke obtained with
10 phr KG-STA was nearly identical to that
obtained with 15 phr of Climax A2017I.
Nearly identical performance advantages
were observed in the 60 phr ATH system.
The performance of KG-STA again far
exceeds the performance of Climax WA
011GA at all use levels.
The total smoke numbers with 5 phr KG-
STA were comparable to those obtained
with Climax WA 011GA at 10 phr.
Significantly, the total smoke obtained with
10 phr KG-STA was nearly the same as that
obtained with 15 phr of Climax A2017I.
Both the Cone Calorimeter and NBS Smoke
results demonstrate that in flexible PVC,
KG-STA offers performance advantages
over commercial AOM. Depending on the
system, it appears that the use of KG-STA
allows for the reduction of 25% to 50%
total AOM while retaining equal or better
smoke suppression.
This could be a very significant benefit to
compounders of low smoke flexible PVC.
5. Conclusions
To meet the stringent smoke requirements
of NFPA 262, PVC plenum jacket compound
requires the use of smoke suppressants.
A number of molybdate-based materials
have been utilised to suppress smoke.
These molybdate-based additives function
in the condensed phase by enhancing char
formation.
Sherwin-Williams Chemicals has deve-
loped a process for the precipitation of
high surface area AOM.
The presence of certain talc fillers
influences the morphology of the
precipitated AOM and promotes the
formation of high surface area product.
NBS and cone calorimeter testing have
demonstrated a performance enhance-
ment associated with increased molybdate
surface area.
Data suggests that when compared with
conventional AOM, Kemgard STA can be
used at equal loading with enhanced
performance or at reduced levels with
equivalent performance.
With molybdenum prices at an all-
time high, the ability to reduce use
level by control of particle size and mor-
phology represents a significant technical
achievement. n
6. Acknowledgements
The authors would like to thank Mr Charlie
Simpson and Dave Klimovich for their
technical assistance.
7. References
[1] W H Starnes Jr and E Edelson, Macromolecules
12(5) 797-802 (1979).
[2] W H Starnes Jr, ‘Mechanism of Polyvinyl Chloride
Flame Retardance by Molybdenum (VI) Oxide’ in
Polymer Additives, J E Kresta (ed) Plenum Press,
New York (1984).
[3] J D Innes and A W Cox, ‘The Mechanism of
Smoke Suppression and Synergism of Molybdate
Compounds’ 23rd International Conference of
Fire Safety, January 1996.
[4] US Patent 4,762,700.
[5] US Patent 6,235,261.
[6] J K Walker, ‘Influence of Molybdates on Char
Formation and Smoke Suppression in PVC.’
Additives 2001, Hilton Head SC.
[7] J K Walker, ‘W-K, Ho and M Mittleman, ‘Smoke
Suppression in PVC Plenum Cable Jackets.’ Wire
Focus 2005, Providence, RI.
[8] US Patent Applied.
The Sherwin-Williams Company
4988 Aultman Road
North Canton
Ohio, USA
Tel: +1 330 966 9385
Fax: +1 330 966 7580
Website:
Figure 9: Total smoke for KG-STA and
commercial AOM at 30 phr ATH and 70 k/W/m²
▲ Figure 10: Total smoke for KG-STA and
commercial AOM at 60 phr ATH and 70 k/W/m²
▲