The Use of Molybdates in Antimony-Free Flexible PVC Compound

The Use of Molybdates in Antimony-Free Flexible PVC CompoundJ. Ken Walker, Wai-Kwong HoSherwin-Williams Chemicals601 Canal Rd.Cleveland, Ohio 44113+1-216-566-2944 · jkwalker@sherwin.comABSTRACTWire and cable applications of flexible PVC typically must meetvarious flame and smoke standards. Historically, antimony oxidehas been added to reduce flammability of plasticized PVC.Antimony oxide has been shown to enhance flame retardancy viaa gas phase mechanism involving the scavenging of free radicals.The enhanced flame retardancy is also accompanied by anincrease in smoke generation. In recent years, environmental andtoxicity concerns have led the wire and cable industry to pursuealternative flame retardant additives. Particularly in Europe, therehas been a strong push to develop antimony-free flexible PVCcompound.Molybdates have been shown to promote char formation duringcombustion by the Friedel-Crafts alkylation of alkene linkagesthat are formed during PVC thermolysis. In this work, weexamine the FR effectiveness of various environmentally friendlymolybdate additives in flexible PVC. Heat release capacitieswere determined using a Microcombustion calorimeter and smokegeneration was determined according to ASTM E662, the NBSSmoke Chamber. Strategies to achieve FR performance with nonantimonyadditives are presented.Keywords: PVC, antimony-free, flame retardants, char formation,smoke suppression, jacket compound, microcalorimeter,pyrolysis.1. INTRODUCTIONAntimony oxide has been used for many years to reduce flamespread in PVC wire and cable applications. However, mountingenvironmental and toxicity concerns have led the industry topursue alternative flame retardant additives. One approach toreducing flame spread in antimony-free systems is through the useof additives to promote the formation of char. A number of zinccompounds (zinc oxide, zinc borate, zinc stannate) have beenused in PVC to promote char formation. These are known topromote the dehydrochlorination of PVC that initiates chemicalcrosslinking. Molybdenum (VI) oxide and related compounds arechar forming additives that function as smoke suppressants,MoO 3 has been shown to react with the HCl produced by thepyrolysis of PVC to form MoO 2 Cl 2 , a potent Lewis acid. Thiscan then promote crosslinking in a number of ways [1,2,3]. Onelikely mechanism is the Friedel-Crafts alkylation of alkenelinkages that are formed during PVC thermolysis (eq 1) [1,2,3].ClCH=CHCHz = Lewis acid+zCH=CH CH=CHCHC=CH + HCl (1)Another approach to crosslinking is the use of reductive couplingagents. These are low-valent metal species that promote reductivecoupling of the polymer according to eq 2 [4].2ClCH=CHCH+ M n CH=CHCHCHCH=CH + M n+2 Cl 2 (2)The coupling process is potentially catalytic, because thecondensed phase of the burning polymer constitutes a reducingenvironment that can convert the higher-valent form of the metalback to the M n state [5,6]. Work by Starnes et. al. have shownthat various copper compounds can function as reductive couplingagents. Recent research efforts at William and Mary have focusedon mixed-metal copper complexes (i. e., copper complexescontaining a second metal) [7-10]. Various copper mixed metaloxides have exhibited mutual synergism for the suppression ofsmoke and, in some cases, for flame retardancy.In this work, we examine the influence of environmentallyfriendly char forming additives on heat release in various flexiblePVC compounds. Initial screening was conducted using PyrolysisCombustion Flow Calorimetry, a micro-technique designed tomeasure heat release in polymeric systems. Results suggest thatthe use of char forming additives can improve the flameretardancy of flexible PVC and could potentially be used toeliminate antimony oxide from PVC insulation and cable jacketcompound.2. MATERIALSA number of commercial char forming additives were included inthis work. These are listed in Table 1 below.Product Manufacturer ChemistyKemgard 911A Sherwin-Williams Chemicals Zinc Calcium MolybdateKemgard 911C Sherwin-Williams Chemicals Zinc MolybdateKemgard HPSS Sherwin-Williams Chemicals Basic Zinc MolybdateKemgard STA Sherwin-Williams Chemicals Ammonium OctomolybdateKemgard 501 Sherwin-Williams Chemicals Calcium MolybdateKemgard 981 Sherwin-Williams Chemicals Zinc PhosphateZinc Stannate Alcan Chemicals Zinc Hydroxy StannateZinc Borate Rio Tintos Zinc BorateZinc Oxide Horsehead Zinc Zinc OxideTable 1. Commercial Char Forming Additives.Mixed metal copper oxides were prepared at the College ofWilliam and Mary, under the direction of Prof. William Starnes.[4]. Copper molybdate (CuMo) was precipitated from solutions ofNa 2 MoO 4 and CuSO 4. The suspension was heated under refluxovernight, and the pale green precipitate was collected by vacuumInternational Wire & Cable Symposium 197 Proceedings of the 56th IWCS

filtration. Other mixed-metal Cu(II) oxides, CuSnO 3 (CuSn), andCuTi 3 O 7 (CuTi), were similarly prepared.All flexible PVC compounds were based on the formulation, asshown in Table 2. The PVC resin, Oxvinyl 240F, had an inherentviscosity of 1.02, a relative viscosity of 2.37, and a K value of 70.Two different plasticizers were used, dioctyl phthalate fromEastman Chemicals and Santicizer 2148, a alkyl/aryl phosphateester, from Ferro. All formulations contained 50 parts of Micral9400, an untreated alumina trihydrate from Huber.Table 2. Typical flexible PVC formulation.Ingredient Parts by weight SupplierPVC Resin 100 OxyvinylsTin Stabilizer 1.5 Rohm & HaasSynergist 6 VariousAluminaTrihydrate50 HuberSanticizer 2148 50/0 FerroDioctyl Phthalate 0/50 EastmanThe flexible PVC specimens were fused using a 75-mLBrabender Plasti-Corder Digi-System equipped with Type 6 rollerblades (3:2 speed ratio). The fusion process parameters included amixing temperature of 160 0 C and a mixing time of 5 minutes.The fused samples were compression molded with a Carver pressat 300 0 F.3. TEST METHODS3.1 Pyrolysis Combustion Flow CalorimeterLyon, Walters and coworkers at the Federal AviationAdministration Laboratory recently developed PyrolysisCombustion Flow Calorimeter (PCFC) to study, on a small scale,the FR properties of polymeric materials. Pyrolysis (condensedphase) and combustion (gas phase) processes are separatelyreproduced in a nonflaming test. In the first step, the specimen isheated at a constant rate in a pyrolyzer and the degradationproducts are swept away by an inert N 2 gas. The gas stream isthen mixed with oxygen in a combustion zone at 900 0 C wherethe degradation products are completely oxidized. Heat releaserates are then determined by oxygen depletion. Heat releasecapacity (HRC) is defined as the maximum heat release ratedivided by the heating rate. For systems such as PVC thatexhibit two maxima, the heat release capacity is the sum ofthe two heat release rates. The total heat release (THR) is theintegral of the heat release rate/time curve. Lyon and coworkershave shown for pure polymers a correlation between PCFCparameters and FR tests such as UL94, limiting oxygen index andthe cone calorimeter.3.2 NBS Smoke Chamber Measurements.The smoke generated by the combustion of the plaques wasdetermined by using the National Bureau of Standards (NBS)Smoke Chamber method, standardized in the United States asASTM-E662. Test plaques (75 x 75 x 3 mm) were subjected to aradiant heat flux of 25 kW/m 2 , and all tests were run in theflaming mode. The maximum smoke density as well as thesmoke density at various times were recorded; average deviationsfor duplicate burns generally were ≤10%.4. RESULTS4.1 Dioctyl Phthalate Plasticized PVCIn the Pyrolysis Combustion Flow Calorimeter, heat release rateis determined as a function of pyrolysis temperature. Figure 1shows representative curves obtained with pure PVC resin as wellas a filled, DOP plasticized PVC compound (no synergist). PurePVC resin exhibits two stages of decomposition. The first peakwith a maximum at 330 0 C corresponds to the initialdehydrochlorination process that results in the formation of across-linked char. The second, larger peak, at approximately 480 oC corresponds to the thermal decomposition of the char layer.The pyrolysis behavior in the plasticized PVS system is somewhatdifferent. In this system, the first peak is much larger and occursat lower temperature (300 0 C) than that of the neat resin. Thispeak is likely the result of several processes including pyrolysis ofplasticizer as well as the initial pyrolysis of the PVC resin. Thesecond peak in the plasticized system is smaller than that of theneat resin but occurs at approximately the same temperature. Inboth systems, the second peak likely corresponds to the thermaldecomposition of a PVC char. However, in the filled/plasticizedsystem, the magnitude is smaller since PVC is only 50% of thetotal composition.HHR (W/g)15010050DOP PVC0150 350 550Temperature (C)PVCFigure 1. PCFC Comparison of PVC resin and DOP plasticizedPVC compound.A total of 14 synergists or synergist combinations werecompounded into a model flexible PVC compound. This modelcompound consisted of 50 parts dioctyl phthalate, 50 parts ATH,1.5 parts of a tin stabilizer and 6 parts of the synergist. As acontrol, the 6 parts of synergist were replaced with 6 parts ofCaCO3 inert filler. Table 3 shows PCFC data for the varioussystems. Also shown are LOI results, determined according toASTM D 2863.The addition of antimony oxide to the DOP plasticized compoundincreased the LOI from 28 for the control compound to 37.However, the HRC and THR determined by PCFC were verysimilar to that of the control compound containing CaCO3. Themechanism for antimony/halogen synergy is known to involvegas phase free radical inhibition of flame reactions. Therefore, itis clear that the PCFC is insensitive to vapor phase mechanisms offlame retardancy. Lyon et. al. have discussed this aspect of PCFCand have gone on to demonstrate that the technique is sensitive tocondensed phase processes such as char formation.International Wire & Cable Symposium 198 Proceedings of the 56th IWCS

PVC 100DOP 50ATH 50Tin Stab. 1.5Synergist 6373533CaCO3 Sb2O3 911A HPSS STA 981 911C 501HRC 206 206 336 400 479 489 462 205THR 12.4 12.5 11 10 10 10.7 10.6 11.7Peak 1 Temp 301 291 284 272 276 273 276 298Peak 1 Area 8.05 7.48 7.47 6.14 6.72 6.68 7.07 7.88Peak 3 Temp 486 483 482 481 477 489 483 483Peak 3 Area 4.33 3.71 3.41 3.73 3.24 4.03 3.47 3.94LOI3129R 2 = 0.717527258 8.5 9 9.5 10 10.5 11 11.5 12 12.5 13Total HeatLOI 28 37 30 32 33 28 29 28ZHS ZB CuMo CuSn CuTi ZnO CuMo/HPSSHRC 709 528 417 316 214 372 276THR 10.2 11.2 9.3 9.8 10.6 7.8 8.9Peak 1 Temp 268 274 265 272 281 263 270Peak 1 Area 6.3 7.32 7.06 6.58 7.17 4.79 5.63Peak 3 Temp 484 485 473 480 484 485 479Peak 3 Area 3.92 3.98 2.16 3.21 3.46 4.32 3.28Figure 2. PCFC Total Heat Release vs. LOI for DOPPlasticized PVC.600500400300DOP PlasticizerPower (DOP Plasticizer)200LOI 33 31 33 33 31 31 35100Table 3. PCFC and LOI Data for DOP Plasticized PVC.The PCFC does appear to differentiate between the other FRsynergists, all of which are believed to function by promotingchar formation. To differing degrees, all of the char formingadditives also enhanced the limiting oxygen index. Of thesingle synergist systems, the highest LOI (33) was achievedwith Kemgard STA (ammonium octomolybdate), coppermolybdate and zinc stannate. These three also exhibited lowtotal heat release in the PCFC. Figure 2 demonstrates thecorrelation between LOI and THR for the 14 antimony-freesystems.The PCFC heat release curves themselves provided interestingcomparisons between the various synergists. All synergistsreduced the char formation temperature compared to the control,with ZnO showing the greatest reduction (see Table 1). ZnO isknow to catalyze the dehydrochlorination of PVC and diminishthermal stability. The effect of ZnO on pyrolysis of PVC can beseen in Figure 3.The onset of pyrolysis in the ZnO system is actually precededby the formation of non-combustible gasses (HCl) that appearsas a negative heat release rate. The subsequent combustion peakis much sharper and lower in area than the control. Interestinglythe second peak attributed to thermal decomposition of thecharred PVC is not affected by the presence of ZnO.Two of the best performing systems, KG STA and coppermolybdate are shown in Figure 4, along with the control.0-100-200150 200 250 300 350 400 450 500 550 600TemperatureContr olFigure 3. PCFC Curves of DOP Plasticized PVC: ZnO vs.Control.500450400350300250200150100500150 200 250 300 350 400 450 500 550 600 650ZnOTemperature (C)CaCO3 Filler Copper Molybdate KG STAFigure 4. PCFC curves of DOP plasticized PVC: KG STA andcopper molybdate vs. control.International Wire & Cable Symposium 199 Proceedings of the 56th IWCS

Like ZnO, these additives reduced the char formationtemperature and also the area of the first pyrolysis peak.However, unlike ZnO, both also reduced the area of the secondpyrolysis peak, indicating that both additives promote theformation of a more thermally stable char. KG STA was moreeffective than copper molybdate in decreasing the total heatrelease from the first pyrolysis step, but copper molybdate wasmore effective in decreasing the area of the second peak. Thisdifference in behavior suggests differing mechanisms that maygive rise to further synergy.The potential synergy through the use of two char formingadditives can been seen by examination of the systemcontaining KG HPSS and copper molybdate. This combinationachieved an LOI of 35, approaching that of the antimony oxidesystem. The KG HPSS/copper molybdate system also exhibitedthe lowest THR of any of the systems examined. Figure 5presents the PCFC curves for KG HPSS, copper molybdate andthe combination of the two. It can be seen that first pyrolysispeak with the combination of KG HPSS and copper molybdatewas lower in area than either of the two materials alone. Thearea of the second peak for the combination was intermediatethat of the two additives alone.thermal stability of PVC char. This is also consistent with theuse of Santicizer 2148 to lower smoke in PVC plenum cablejacket formulations.Both systems exhibited two peaks. The first peak for bothsystems occurred at approximately the same temperature. Thepeak height and peak were slightly lower for the samplecontaining the phosphate ester. However, a shift toward highertemperature was observed for the second peak in the systemcontaining 2148. The peak area was also lower. Since this peakis believed to correspond to the thermal decomposition of thePVC char, we conclude that the phosphate moiety increases thethermal stability of PVC char. This is also consistent with theuse of Santicizer 2148 to lower smoke in PVC plenum cablejacket formulations.18 016 014 012 010 0806040204003500150 200 250 300 350 400 450 500 550 600 650Temperature (C)300DOP Con t r ol2148 ControlHRR (W/g)250200150100500150 200 250 300 350 400 450 500 550 600 650Temperature (C)CaCO3 HPSS CuMo HPSS/CuMo BlendFigure 5. PCFC Curves of DOP Plasticized PVC: KG HPSS,CuMo and Blend vs. Control.4.2 Phosphate Ester Plasticized PVCA number of FR plasticizers are available in the marketplace,including brominated phthalates, phosphate esters etc. In thisstudy we utilized the PCFC to study the influence of Santicizer2148 on heat release rates in flexible PVC systems. Figure 6compares PCFC curves for two flexible PVC systems. Onesystem was compounded with 50 phr DOP and the secondsystem was compounded with 50 phr Santicizer 2148. Bothsystems also contained 50 phr ATH and 6 phr CaCO3.Both systems exhibited two peaks. The first peak for bothsystems occurred at approximately the same temperature. Thepeak height and peak were slightly lower for the samplecontaining the phosphate ester. However, a shift toward highertemperature was observed for the second peak in the systemcontaining 2148. The peak area was also lower. Since this peakis believed to correspond to the thermal decomposition of thePVC char, we conclude that the phosphate moiety increases theFigure 6. PCFC Curves of DOP and Santicizer 2148Plasticized PVC.A total of 14 synergists or synergist combinations werecompounded into a model flexible PVC compound containingSanticizer 2148 plasticizer. As in the earlier study, the modelcompound also contained 50 parts ATH, 1.5 parts of a tinstabilizer and 6 parts of the synergist. As a control, the 6 partsof synergist were replaced with 6 parts of CaCO3 inert filler.Table 4 shows PCFC data for the various systems along withLOI results, determined according to ASTM D 2863.Table 4. PCFC and LOI Data for Santicizer 2148 plasticizedPVC compounds.Number CaCO3 Sb2O3 911A HPSS STA 981 911C ZHS ZBHRC 236 277 394 347 289 571 400 440 388Total Heat 14.3 13.2 12.7 11.8 11.7 11.4 12.3 11.6 11.6Peak 1 Temp 302 307 285 290 295 275 287 280 278Peak 1 Area 8.71 8.18 7.93 7.24 8.25 7.28 7.81 7.33 7.24Peak 3 Temp 475 477 480 481 480 484 483 487 486Peak 3 Area 5.6 5.06 4.81 4.55 3.5 4.14 4.53 4.31 4.38LOI 33 34 32 31.5 37 30.5 32 31.5 30.5Number CuMo CuSn CuTi ZnOCuMo/HPSS CuMo/STACuMo/CuSn CuMo/CuTiHRC 285 367 317 519 301 307 331 334Total Heat 10 10.7 12.4 10.6 11 10.2 11.1 10.9Peak 1 Temp 280 276 287 270 280 285 277 278Peak 1 Area 7.27 7.25 8.16 6.5 7.49 7.28 7.92 7.86Peak 3 Temp 481 486 483 486 482 482 485 485Peak 3 Area 2.72 3.49 4.26 4.09 3.53 2.91 3.16 3.03LOI 32 30.5 33 29.5 33 32 32 32International Wire & Cable Symposium 200 Proceedings of the 56th IWCS

There were several interesting features in the LOI results. TheLOI for the control was much higher than that of the DOPcontrol (33 vs. 28). This result clearly demonstrates the FReffectiveness of the phosphate ester plasticizer. This is likelydue to the enhanced thermal stability of the PVC char. Anunexpected observation was that antimony oxide onlymarginally increased the LOI. This result is not well understoodand further work is needed to examine the function of antimonyoxide at different levels.30025020015 010 050All of the other char forming synergists lowered the THRcompared to the control. However, most of the synergistssignificantly increased the HRC – the two with the least effectbeing KG STA and copper molybdate. Also to varying degrees,all of the synergists shifted the first pyrolyis peak to lowertemperatures. ZnO showed the largest shift in peak temperaturewhile KG STA showed the smallest temperature shift.Nearly all of the synergists lowered the LOI compared to thecontrol. It appears that the lowest LOI’s were observed in thesystems that showed the largest shift in peak temperature for thefirst pyrolysis. Figure 7 shows that there appears to be acorrelation between the temperature of the first pyrolysis peakand LOI. The KG STA system proved to be the only systemwith an LOI higher than the control (37 vs. 34) and was alsohigher than that of the antimony oxide system. KG STA wasalso the additive with the least affect on peak temperature.LOI3836343230R 2 = 0.63020200 250 300 350 400 450 500 550 600Temperat ure ( C)CaCO3 HPSS STA CuM oFigure 8. PCFC curves of 2148 plasticized PVC: KG HPSS,KG STA and CuMo vs. Control.4.3 NBS Smoke – Phosphate Ester PlasticizerInorganic molybdates are the industry standard for smokesuppression in PVC. The maximum smoke density, determinedaccording to ASTM E662 is shown for five samples, allcontaining 50 phr Santicizer 2148 and 50 phr ATH. Theaddition of antimony oxide increased the maximum smokedensity developed. when compared to the control compound.The effect of antimony oxide on smoke development in PVC iswell known and has been attributed its vapor phase mechanismof action. All of the other molybdate based synergistssignificantly lowered the maximum smoke density to varyingdegrees. Figure 9 shows the effectiveness of three molybdatebase materials, KG HPSS, KG STA and copper molybdate.2826270 275 280 285 290 295 300Peak Temperature (C)700NBS Smoke DmaxFigure 7. Peak temperature vs. LOI for Santicizer 2148plasticized PVC compounds.The best performing system, KG STA, is compared to KGHPSS and copper molybdate in Figure 8. The majordistinguishing feature is the temperature of the first pyrolysisreaction. The total heat associated with the first peak wasactually lowest with KG HPSS, the system with the lowest LOI.All three of these additives did reduce total heat associated withthe second pyrolysis peak, again indicating that these additivescan produce a more thermally stable char. The most effectiveadditive in terms of the the second pyrolysis peak was veryclearly copper molybdate.6005004003002001000Cont rol Sb2O3 HPSS STA CuMoFigure 9. Maximum Smoke Density for 2148 plasticized PVC.The most effective smoke suppressant in the study was coppermolybdate. As shown in Figure 8, copper molybdate was alsomost effective in lowering the total heat associated with thethermal decomposition of the PVC char.International Wire & Cable Symposium 201 Proceedings of the 56th IWCS

5. CONCLUSIONSPyrolysis Combustion Flow Calorimetry has been used to studythe influence of various additives on heat release rate inantimony- free flexible PVC systems. In DOP plasticized PVC,nearly all of the char promoting additives lowered total heatrelease and also increase LOI. Additives based on coppermolybdate, ammonium octomolybdate and basic zinc molybdatechemistries appeared to be most effective. However, at equalloading no single chemistry could achieve the same LOI asantimony oxide.PCFC studies show that plasticized PVC exhibits two stages ofdecomposition. The major heat release occurs at roughly 300 o Cis likely the result of several processes including pyrolysis ofplasticizer as well as the initial pyrolysis of the PVC resin. Thesecond peak occurring at approximately 475o C is smaller andlikely corresponds to the thermal decomposition of a PVC char.While most additives appeared to reduce heat release during theinitial pyrolysis of PVC, copper molybdate, and to a lesserextent ammonium octomolybdate, was notably effective atlowering the heat release due to the thermal decomposition ofchar. This likely accounts for their effectiveness for smokesuppression. Some synergy between char forming additives wasnoted and should be investigated further. This synergy is likelydue to differences in char formation mechanisms.The use of an alkyl/aryl phosphate ester plasticizer, rather thanan octyl phthalate, does dramatically increase LOI. This is dueto the influence of the phosphate moiety on char formation.Antimony oxide does not appear to significantly enhance LOIwhen used in combination with the phosphate ester. Thissuggests that the FR effects of these materials are not additive.Similarly, most of the char forming additives actuallydiminished LOI. Of the char forming additives, onlyammonium octomolybdate improved LOI. In fact, when used incombination with a phosphate ester plasticizer, ammoniumoctamolybdate will produce an LOI greater than that ofantimony oxide.Because of its vapor phase mechanism of action, the use ofantimony oxide in PVC results in high levels of smoke. On theother hand, molybdates are the industry standard for smokesuppression and have been used in low smoke PVC applicationsfor many years. The development of a low-smoke, antimonyfreePVC compound that relies on molybdate promoted charformation would be a significant advancement to the wire andcable industry.7. REFERENCES1. Starnes, W. H., Jr.; Edelson, D. Macromolecules 1979, 12,797.2. Starnes, W. H. Jr.; Wescott, L. D., Jr.; Reents, W. D., Jr.;Cais, R. E.; Villacorta, G. M.; Plitz, I. M.; Anthony, L. J.In Polymer Additives; Kresta, J. E., Ed.; Plenum: NewYork, 1984; p 237.3. Wescott, L. D., Jr.; Starnes, W. H., Jr.; Mujsce, A. M.;Linxwiler, P. A. J. Anal. Appl. Pyrol. 1985, 8, 163.4. Pike, R. D.; Starnes, W.H., Jr.; Jeng, J. P.; Bryant, W. S.;Kourtesis, P.; Adams, C. W.; Bunge, S. D.; Kang, Y. M.;Kim, A. S.; Kim, J. H.; Macko, J. A.; O’Brien, C. P.Macromolecules 1997, 30, 6957.5. Lattimer, R. P.; Kroenke, W. J. J. Appl. Polym. Sci. 1981,26, 1191.6. Lattimer, R. P.; Kroenke, W. J. In Analytical Pyrolysis:Techniques and Applications; Voorhees, K. J., Ed.;Butterworths: Woburn, MA, 1984; p 453.7. Starnes, W. H., Jr.; Pike, R. D.; Cole, J. R.; Doyal, A. S.;Kimlin, E. J.; Lee, J. T.; Murray, P. J.; Quinlan, R. A.;Zhang, J. Polym. Degrad. Stab. 2003, 82, 15.8. Starnes, W. H., Jr.; Pike, R. D.; Brown, A. H.; Fuller, T.W.; Quinlan, R. A.; Showalter, T. B.; Taylor, K. M.;Zhang, J. Polym. Mater. Sci. Eng. 2004, 91, 215.9. Starnes, W. H., Jr.; Pike, R. D.; Brown, A. H.; Fuller, T.W.; Lee, J. T.; Quinlan, R. A.; Showalter, T. B.; Taylor, K.M.; Zhang, J. In Proceedings, 32 nd Annual Conference ofthe North American Thermal Analysis Society (2004);Symposium on Flame Retardancy, Paper No. 1.10. Starnes, W. H., Jr.; Pike, R. D.; Brown, A. H.; Lee, J. T.;Showalter, T. B.; Taylor, K. M.; Zhang, J. In Proceedings,Additives 2004 Conference; Executive ConferenceManagement: Plymouth, MI, 2004; Chapter 1.6. ACKNOWLEDGEMENTSThe authors would like to thank Professors William Starnes andRobert Pike for the samples of copper mixed metal oxides andfor technical disscusions.International Wire & Cable Symposium 202 Proceedings of the 56th IWCS

8. AUTHORSMr. Wai-Kwong HoDr. J. Ken WalkerKen Walker is a staff scientist with the Sherwin-WilliamsCompany. He graduated from Boston University in 1980 with aPh. D. in physical chemistry and has 25 years of industrialresearch experience with both Diamond Shamrock Corp. andSherwin-Williams. For the past six years, Ken has directed theR&D effort for the Sherwin-Williams Chemical Business Unit.Mr. Wai-Kwong Ho is a scientist with the Sherwin-WilliamsCompany. He received his B.S. in Chemical Engineering fromPolytechnic University. Wai-Kwong has worked for more than20 years in the field of plastics, chemicals, adhesives, paints andcoatings. Wai-Kwong and Ken are co-inventors of a costefficient ammonium octoamolybdate (Kemgard STA) and othersmoke suppressants.International Wire & Cable Symposium 203 Proceedings of the 56th IWCS