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Synergies of Metal Molybdates and Metal Hydroxides in Fire Retardant Polyolefin Compounds
Alex Isarov, David Temples, Mark Herndon, Tong Chen J.M. Huber Corporation Fairmount, GA 30139 USA
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 2 Background Information
J.M. Huber Corporation acquired the Kemgard® product line from The Sherwin Williams Company in August 2010.
Kemgard materials are smoke suppressants and char formers based on molybdenum and phosphorous chemistries.
Currently, the main application for Kemgard products is in PVC formulations (rigid, flexible, plastisols).
Huber is investigating Kemgard performance benefits in other polymer systems including polyolefin-based formulations.
Objective – review available data related to FR performance of metal molybdates as fire retardants/char formers in polyolefin based formulations.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 3 Presentation Outline
Review of Kemgard technology – precipitation of active phase on the surface of particulate core.
Example – zinc molybdate/zinc borate complex.
Molybdates as char formers in thermoplastic EVA.
Molybdates as char formers in EVA/LDPE blends (thermoplastic and peroxide cross linked).
Zinc phosphate/zinc oxide complex as char former in peroxide cross linked EVA/LDPE blends.
Conclusions.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 4 Kemgard® Engineered Molybdates
Precipitation of molybdates (Ca, Zn) onto the surface of a ppgyarticulate core significantly increases the active surface area of the molybdate phase resulting in enhanced FR efficacy.
Inert core: Calcium Carbonate core – Kemgard 911A Talc core – Kemgard 911C, Kemgard 1100 Zinc Oxide core – Kemgard 911B FR-active core Magnesium Hydroxide core – Kemgard MZM, Kemgard HPSS. Zinc Borate core – Kemgard 700Z
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 5 Example - Zn Molybdate /Zn Borate Complex
Material Description Sample ID BET surface area ((),measured), m2/gg Zinc borate (core) Zinc borate 2.9
10% zinc molybdate/zinc borate ZMZB-10 5.5
17.4 % zinc molybdate/zinc borate ZMZB-17 5.3
24.8% zinc molybdate/zinc borate ZMZB-24 6.3
Precipitation of Zn molybdate on the surface of Zn borate leads to a significant increase of BET specific surface area
A. Isarov et. al. Proceedings of 60th IWCS, 2011, 250-256
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 6 Example - Zn Molybdate /Zn Borate Complex
Description BET surface Zinc Molybdate area specific surface (measured), area (calculated), m2/g m2/g
Zinc borate 2.9 n/a (core) 10% zinc 5.5 28 molybdate 17.4 % zinc 5.3 16.3 molybdate 24.8% zinc 6.3 16.3 molybdate
Higher surface area of zinc molybdate-zinc borate complex is due to high surface area of Zinc molybdate particle on zinc molybdate particles on zinc borate surface. the surface of zinc borate
A. Isarov et. al. Proceedings of 60th IWCS, 2011, 250-256
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 7 Materials used in this study ¾Metal hydroxides:
Vertex 100 Vertex 100 SP Zerogen 100 Zerogen 100 SP Chemical Identity Magnesium Magnesium Magnesium Magnesium Hydroxide, Hydroxide, Hydroxide, Hydroxide, synthetic synthetic synthetic synthetic Particle size, microns 1.5 1.5 0.8 0.8 BET Surface Area, m2/g 14 14 5 5 Chemical purity Good Good Excellent Excellent Surface Treatment Untreated Vinyl silane Untreated Vinyl silane
¾Molybdates: •Zn molybdate •Ca molybdate •Kemgard MZM – zinc molybdate/magnesium hydroxide complex. •Kemgard 700Z – zinc molybdate/zinc borate complex.
¾Kemgard 981 – zinc ppphosphate/zinc oxide com plex.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 8 Test Formulations: Fire Retardant Polyolefin Compounds
Compound Ingredients 1. EVA 64% MDH 30% EVA (28% VA, 3 MFR) 6% compatabilizer/additives 2EVA/LDPE2. EVA/LDPE 65% MDH 20.7% EVA (28% VA, 3 MFR) 12.8% LDPE (2.3 MFR) 1.5% additives 3. XL-EVA/LDPE 65% MDH 19.3% EVA (28% VA, 3 MFR) 12.8% LDPE (2.3 MFR) 1. 4% organic peroxide 1.5% additives
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 9 FR Test Methods
• Pyrolysis Combustion Flow Calorimeter – Microscale Calorimeter or Micro Combustion Calorimeter – Developed by US FAA – ASTM D7309-07 • Cone Calorimeter – ASTM E1354 (50kW) • Limiting Oxygen Index – ASTM D2863 • UL-94
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 10 Molybdate Promoted Cross-linking in PVC
Dehydrochlorination, polyene formation Cl Cl Δ –(CH2CH)n– –(CH2CH)n-x –(CH=CH)x– + xHCl
Crosslinking Cl Z -CH=CHCH- + -CH=CH- -CH=CHCHC=CH- + HCl
6+ Z = Lewis Acid (Mo surface)
Higher surface area of zinc molybdate is beneficial for efficient char formation
Starnes,,,; W. H., Jr.; Ge, X. Macromolecules 2004, 37, 352-359.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 11 Effect of Zinc Molybdate on Char Formation EVA - 64% total FR loading level
Rate of Heat Release Specific Extinction Area
300 1000 Vertex 100 900 Vertex 100 V100/Zinc Molybdate 4:1 250 800 V100/Zinc Molybdate 4:1 V100/Zinc Molybdate 1:1.5 V100/Zinc Molybdate 1:1.5 700 200
2 600
/kg 500 150 2 w/m M KK 400 100 300 200 50 100 0 0 0 200 400 600 800 0 200 400 600 800 Time (s) Time (s)
Zn Molybdate facilitates char formation in EVA when used in combination with magnesium hydroxide. LOI 37 37 33 Better char formation manifests itself in the reduction UL94 All failed of heat release rate and delay in secondary RHR and smoke peaks.
T. Chen et. al. Proceedings of 58th IWCS, 2009, 569 -576
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 12 Zinc Molybdate Promoted Cross-linking in EVA Friedel-Crafts Alkylation
O C CH3 O Z -CH=CHCH- + -CH=CH- -CH=CHCHC=CH- + CH3COOH
6+ Z = Lewis Acid (Mo surface) Crosslinking mechanism similar to PVC, surface of zinc molybdate (Mo6+) catalyzes FC alkylation reaction.
Does Zn play any role? T. Chen et. al. Proceedings of 58th IWCS, 2009, 569 -576
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 13 Effect of Ca Molybdate on Char Formation EVA - 64% total FR loading level
Rate of Heat Release Specific Extinction Area
400 1200 Vertex 100 Vertex 100 350 V100/Ca Molybdate 4:1 1000 V100/Ca Molybdate 4:1 300 V100/Ca Molybdate 1.5:1 800 V100/Ca Molybdate 1.5:1
2 250 g kk mm /
200 2 600 M Kw/ 150 400 100 200 50 0 0 0 100 200 300 400 500 600 0 100 200 300 400 500 600 Time (s) Time (s)
Ca molybdate is not as efficient as Zn molybdate LOI 31 34 37 in char formation in EVA when used in UL94 All failed combination with magnesium hydroxide.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 14 Ca Molyyybdate vs. Zinc Molybdate in EVA EVA - 64% total FR loading level
Rate of Heat Release Specific Extinction Area 300 Vertex 100 1200 Vertex 100 V100/Ca Molybdate 4:1 V100/Ca Molybdate 4:1 250 1000 V100/Zn Molybdate 4:1 V100/Zn Molybdate 4:1 200 800 2 150 /kg 600 22 mm 100 m 400 kW/ 50 200 0 0 0 200 400 600 800 0 200 400 600 800 Time, second s Time, second s
Zn molybdate is a more efficient char former in LOI 34 37 37 the rm oplast i c EVA as com par ed to Ca m ol ybdate. UL94 All failed Synergy between zinc and molybdenum in EVA.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 15
Effect of ZnO and MoO3 on Char Formation in EVA EVA - 64% total FR loading level
Rate of Heat Release Rate of Smoke Production 350 10 Zerogen 100 SP Zerogen 100 SP 9 300 Z100 SP/ZnO 4:1 Z100 SP/ZnO 4:1 8 Z100 SP/MoO3 4:1 250 Z100 SP/MoO3 4:1 7 6 2 200 m
// 5 ss
150 1/ kW 4 3 100 2 50 1
0 0 0 200 400 600 800 0 200 400 600 800 Time, seconds Time, seconds
Molybdenum oxide is a much better char former LOI 45 44 42 in thermoplastic EVA as compared to Zinc oxide. UL94 V0 Fail Fail Synergy between zinc and molybdenum in EVA.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 16 Effect of Zn Molybdate/MDH Complex on Char Formation EVA - 66% tota l FR l oadin g l ev el
Rate of Heat Release (50 kW) Rate of Smoke Production
250 2.5 Vertex 100/KG MZM 5:1 (66%) Vertex 100/KG MZM 5:1 (66%) Vertex 100 (66%) 200 202.0 Vertex 100 (66%)
150 2 1.5 1/s
kW/m 100 1.0
0.5 50 0.0 0 0 200 400 600 800 1000 0 200 400 600 800 1000 Time (s) Time (s)
LOI 41 41 Kemgard MZM – Zn molybdate/MDH complex. UL94 V0 V0 Partial replacement of Vertex 100 SP magnesium hydroxide (~ 17%) with Kemgard MZM leads to the formation of stronger char, which manifests itself in a delay in appearance of secondary HRR and RSP peaks.
T. Chen et. al. Proceedings of 58th IWCS, 2009, 569 -576
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 17 Zinc Molybdate-Zinc Borate Complex in EVA EVA - 64 % total FR l oadin g l ev el
Partial replacement of Vertex 100 magnesium hydroxide with zinc borate significantly reduces heat release rate and rate of smoke production. LOI 37 37 38 UL94 Fail V0 V0 ZMZB-17 is more efficient vs. zinc borate - stronger char manifests itself in an additional delay in the appearance of secondary HRR and RSP peaks. A. Isarov et. al. Proceedings of 60th IWCS, 2011, 250-256
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 18 Effect of Zn Molybdate Level on Rate of Heat Release
EVA - 64% total FR loading level
Increase of Zn molybdate level leads to longer delay in the appearance of the secondary heat release peak indicating formation of stronger char.
Position of secondary peak of heat release Zinc Molybdate – Zinc Borate FR synergy A. Isarov et. al. Proceedings of 60th IWCS, 2011, 250-256
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 19 Pyrolysis Combustion Flow Calorimeter Zinc Molybdate – Zinc Borate Synergy in Char Formation
EVA - 64% total FR loading level 1)Zinc borate does not affect PCFC heat release rate;
2)Zinc molybdate delays the second heat release peak;
3)Zinc molybdate – Zinc borate complex reduces total heat release.
First decomposition step: Second decomposition step: Evolution of acetic acid Degradation of EVA residue AIA. Isarov et . al . P roceedi ngs o f60f 60th IWCS, 2011, 250-256
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 20
Effect of ZnO and MoO3 on Char Formation EVA/LDPE (60/40) blend - total FR loading 65%
Rate of Heat Release Rate of Smoke Production 250 3.0 Zerogen 100 SP Zerogen 100 SP 200 Z100 SP/ZnO 4:1 2.5 Z100 SP/ZnO 4:1 Z100 SP/MoO3 4:1 2.0 Z100 SP/MoO3 4:1 2 150 mm 1.5 1/s
kW/ 100 1.0 50 0.5
0 0.0 0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 Time, seconds Time, seconds
In thermoplastic EVA/LDPE (60/40) blend, both Zinc oxide and Molybdenum oxide facilitate char formation. LOI 39 39 37 UL94 V0 V0 V0 Presence of LDPE increases char forming efficiency of ZnO.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 21 Effect of Zn Molybdate on Char Formation
EVA/LDPE (60/40) blend - total FR loading 65%
Rate of Heat Release Rate of Smoke Production 250 3.0 Zerogen 100 SP Zerogen 100 SP 2.5 200 Z100 SP/Zn Molybdate 4:1 Z100 SP/Zn Molybdate 4:1 2.0 2 150 m ss 1.5 1/
kW/ 100 1.0
50 0.5
0 0.0 0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 Time, seconds Time, seconds
Zn molybdate is as efficient a char former in thermoplastic EVA/LDPE (60/40) blend as it is in 100% EVA. LOI 39 39
This suggests a second char forming mechanism UL94 V0 V0 involving Zn and LDPE.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 22 Zn Molybdate vs. Ca Molybdate as Char Formers in Peroxide Cross-linked EVA/LDPE
XL-EVA/LDPE (60/40) blend - total FR loading 65%
Rate of Heat Release Rate of Smoke Production 250 3.5 Zerogen 100 SP Zerogen 100 SP 3.0 200 Z100 SP/Zn Molybdate 4:1 Z100 SP/Zinc Molybdate 4:1 2.5 Z100SP/Ca Molybdate 4:1 Z100 SP/Ca Molybdate 4:1 2 150 202.0 mm
1/s 1.5 kW/ 100 1.0 50 0.5
0 0.0 0 200 400 600 800 1000 0 200 400 600 800 1000 Time, seconds Time, seconds
In peroxide cross-linked EVA/LDPE (60/40) blend Zn molybdate is a more efficient char former compared to Ca molybdate. LOI 46 43 41 Same trend was observed in thermoplastic EVA and thermoplastic UL94 V0 V0 Fail EVA/LDPE blend.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 23 Zinc Phosphate/Zinc Oxide Complex (Kemgard 981)
Description BET surface Zinc phosphate area specific surface (measured), area (calculated), m2/g m2/g
Zinc oxide 1.2 n/a (core) 30% Zinc 3.2 7.9 phosphate
The higher surface area of the Zinc phosphate-Zinc oxide complex is due to the high surface area of Zinc phosphate particles on the Zinc oxide surface. Zinc phosphate particles on the surface of Zinc oxide
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 24 Zn Phosphate – Zinc Oxide Complex in Peroxide Cross-linked EVA/LDPE
XL-EVA/LDPE (60/40) blend - total FR loading 65%
Rate of Heat Release Rate of Smoke Production 250 3.0 Zerogen 100SP Zerogen 100SP 200 2.5 Z100SP/5% KG 981 Z100SP/5% KG 981 2.0 2 150 mm 1.5 1/s
kW/ 100 1.0 50 0.5
0 000.0 0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 Time, seconds Time, seconds
Zinc phosphate/zinc oxide complex facilitates char formation in peroxide cross-linked EVA/LDPE blends at lower MDH replacement levels (5%). LOI 44 43 UL94 V0 V0 Improved char formation was not observed at higher MDH replacement levels.
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 25 Conclusions Zinc molybdate contributes to char formation in EVA formulations by promoting cross-linking during EVA decomposition. Proposed mechanism – Friedel-Crafts alkylation catalyzed by Mo6+.
The FR performance of magnesium hydroxide in EVA can be improved by replacing part of MDH with a Zn molybdate/MDH complex (Kemgard MZM) or a Zn molybdate/Zn borate complex (Kemgard 700Z).
In formulations containing LDPE (EVA/LDPE blends), Zn2+ ions play an important role in char formation . Possible mechanism – polymer cross - linking via carboxyl groups formed during thermo-oxidative degradation of polyethylene.
Zn phosphate/ZnO complex (Kemgard 981) facilitates char formation in peroxide cross-linked EVA/LDPE blends at lower MDH replacement levels (5%).
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012 26 Thank you for your attention!
Our contact information:
Alex Isarov, David Temples, Mark Herndon J.M. Huber Corporation Fairmount, GA 30139 USA +1-706-337-3243 [email protected] [email protected] mark. herndon@huber. com
23rd Annual BCC Conference: Recent Advances on Flame Retardancy of Polymeric Materials FIRE RETARDANT ADDITIVES May 21-23, 2012