Synergies of Metal Molybdates and Metal Hydroxides in Fire Retardant Polyolefin Compounds

Transcription

1 1 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 USA

2 Background Information 2 J.M. Huber Corporation acquired the Kemgard product line from The Sherwin Williams Company in August 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.

3 Presentation Outline 3 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.

4 Kemgard Engineered Molybdates 4 Precipitation of molybdates (Ca, Zn) onto the surface of a particulate 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

5 Example - Zn Molybdate /Zn Borate Complex 5 Material Description Sample ID BET surface area (measured), m 2 /g Zinc borate (core) Zinc borate % zinc molybdate/zinc borate ZMZB % zinc molybdate/zinc borate ZMZB % zinc molybdate/zinc borate ZMZB 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 60 th IWCS, 2011,

6 Example - Zn Molybdate /Zn Borate Complex 6 Description BET surface area (measured), m 2 /g Zinc Molybdate specific surface area (calculated), m 2 /g Zinc borate (core) 10% zinc molybdate 17.4 % zinc molybdate 24.8% zinc molybdate 2.9 n/a Higher surface area of zinc molybdate-zinc borate complex is due to high surface area of zinc molybdate particles on zinc borate surface. Zinc molybdate particle on the surface of zinc borate A. Isarov et. al. Proceedings of 60 th IWCS, 2011,

7 Materials used in this study Metal hydroxides: 7 Chemical Identity Vertex 100 Vertex 100 SP Zerogen 100 Zerogen 100 SP Magnesium Hydroxide, synthetic Magnesium Hydroxide, synthetic Magnesium Hydroxide, synthetic Magnesium Hydroxide, synthetic Particle size, microns BET Surface Area, m 2 /g Chemical purity Good Good Excellent Excellent Surface Treatment Untreated Vinyl silane Untreated Vinyl silane Molybdates: Zn molybdate Ca molybdate Kemgard MZM zinc molybdate/magnesium hydroxide complex. Kemgard 700Z zinc molybdate/zinc borate complex. Kemgardg 981 zinc phosphate/zinc p oxide complex.

8 Test Formulations: Fire Retardant Polyolefin Compounds 8 Compound Ingredients 1. EVA 64% MDH 30% EVA (28% VA, 3 MFR) 6% compatabilizer/additives 2. 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

9 FR Test Methods 9 Pyrolysis Combustion Flow Calorimeter Microscale Calorimeter or Micro Combustion Calorimeter Developed by US FAA ASTM D Cone Calorimeter ASTM E1354 (50kW) Limiting Oxygen Index ASTM D2863 UL-94

10 Molybdate Promoted Cross-linking in PVC 10 Dehydrochlorination, polyene formation Cl Cl (CH 2 CH) n Δ (CH 2 CH) n-x (CH=CH) x + xhcl Crosslinking Cl -CH=CHCH- + -CH=CH- Z -CH=CHCHC=CH- + HCl Z = Lewis Acid (Mo 6+ surface) Higher surface area of zinc molybdate is beneficial for efficient char formation Starnes, W. H., Jr.; Ge, X. Macromolecules 2004,, 37,,

11 Effect of Zinc Molybdate on Char Formation EVA - 64% total FR loading level 11 Rate of Heat Release Specific Extinction Area Kw/m Vertex 100 V100/Zinc Molybdate 4:1 V100/Zinc Molybdate 1: Time (s) M 2 /kg Vertex 100 V100/Zinc Molybdate 4:1 V100/Zinc Molybdate 1: Time (s) Zn Molybdate facilitates char formation in EVA when used in combination with magnesium hydroxide. Better char formation manifests itself in the reduction of heat release rate and delay in secondary RHR and smoke peaks. LOI UL94 All failed T. Chen et. al. Proceedings of 58 th IWCS, 2009,

12 Zinc Molybdate Promoted Cross-linking in EVA Friedel-Crafts Alkylation 12 O C CH 3 O -CH=CHCH- + -CH=CH- Z -CH=CHCHC=CH- + CH 3 COOH Z = Lewis Acid (Mo 6+ surface) Crosslinking mechanism similar to PVC, surface of zinc molybdate (Mo 6+ ) catalyzes FC alkylation reaction. Does Zn play any role? T. Chen et. al. Proceedings of 58 th IWCS, 2009,

13 Effect of Ca Molybdate on Char Formation EVA - 64% total FR loading level 13 Rate of Heat Release Specific Extinction Area m 2 Kw/m Vertex 100 V100/Ca Molybdate 4:1 V100/Ca Molybdate 1.5: M 2 /k kg Vertex 100 V100/Ca Molybdate 4:1 V100/Ca Molybdate 1.5: Time (s) Time (s) Ca molybdate is not as efficient as Zn molybdate in char formation in EVA when used in combination with magnesium hydroxide. LOI UL94 All failed

14 Ca Molybdate vs. Zinc Molybdate in EVA EVA - 64% total FR loading level 14 m 2 kw/m Rate of Heat Release Vertex 100 V100/Ca Molybdate 4:1 V100/Zn Molybdate 4: Time, seconds 2 /kg m Specific Extinction Area Vertex 100 V100/Ca Molybdate 4:1 V100/Zn Molybdate 4: Time, seconds Zn molybdate is a more efficient char former in thermoplastic EVA as compared to Ca molybdate. Synergy between zinc and molybdenum in EVA. LOI UL94 All failed

15 Effect of ZnO and MoO 3 on Char Formation in EVA 15 EVA - 64% total FR loading level /m 2 kw/ Rate of Heat Release Zerogen 100 SP Z100 SP/ZnO 4:1 Z100 SP/MoO3 4:1 1/s Rate of Smoke Production Zerogen 100 SP Z100 SP/ZnO 4:1 Z100 SP/MoO3 4: Time, seconds Time, seconds Molybdenum oxide is a much better char former in thermoplastic EVA as compared to Zinc oxide. Synergy between zinc and molybdenum in EVA. LOI UL94 V0 Fail Fail

16 Effect of Zn Molybdate/MDH Complex on Char Formation EVA - 66% total FR loading level e Rate of Heat Release (50 kw) Vertex 100/KG MZM 5:1 (66%) Vertex 100 (66%) Rate of Smoke Production 2.5 Vertex 100/KG MZM 5:1 (66%) Vertex 100 (66%) kw/m /s Time (s) Time (s) Kemgard MZM Zn molybdate/mdh complex. LOI 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 58 th IWCS, 2009,

17 Zinc Molybdate-Zinc Borate Complex in EVA EVA - 64% total FR loading level e 17 Partial replacement of Vertex 100 magnesium hydroxide with zinc borate significantly reduces heat release rate and rate of smoke production. LOI 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 60 th IWCS, 2011,,

18 Effect of Zn Molybdate Level on Rate of Heat Release 18 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 60 th IWCS, 2011,

19 Pyrolysis Combustion Flow Calorimeter Zinc Molybdate Zinc Borate Synergy in Char Formation 19 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: Evolution of acetic acid Second decomposition step: Degradation of EVA residue A. Isarov et. al. Proceedings of 60 th IWCS, 2011,

20 20 Effect of ZnO and MoO 3 on Char Formation EVA/LDPE (60/40) blend - total FR loading 65% m 2 kw/m Rate of Heat Release Zerogen 100 SP Z100 SP/ZnO 4:1 Z100 SP/MoO3 4:1 1/s Rate of Smoke Production Zerogen 100 SP Z100 SP/ZnO 4:1 Z100 SP/MoO3 4: Time, seconds Time, seconds In thermoplastic EVA/LDPE (60/40) blend, both Zinc oxide and Molybdenum oxide facilitate char formation. Presence of LDPE increases char forming efficiency of ZnO. LOI UL94 V0 V0 V0

21 Effect of Zn Molybdate on Char Formation 21 EVA/LDPE (60/40) blend - total FR loading 65% m 2 kw/ Rate of Heat Release Zerogen 100 SP Z100 SP/Zn Molybdate 4:1 1/s Rate of Smoke Production Zerogen 100 SP Z100 SP/Zn Molybdate 4: 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. This suggests a second char forming mechanism involving Zn and LDPE. LOI UL94 V0 V0

22 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% m 2 kw/m Rate of Heat Release Zerogen 100 SP Z100 SP/Zn Molybdate 4:1 Z100 SP/Ca Molybdate 4:1 1/s Rate of Smoke Production Zerogen 100 SP Z100 SP/Zinc Molybdate 4:1 Z100SP/Ca Molybdate 4: 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. Same trend was observed in thermoplastic EVA and thermoplastic EVA/LDPE blend. LOI UL94 V0 V0 Fail

23 Zinc Phosphate/Zinc Oxide Complex (Kemgard 981) 23 Description BET surface area (measured), m 2 /g Zinc phosphate specific surface area (calculated), m 2 /g Zinc oxide (core) 30% Zinc phosphate 1.2 n/a 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

24 Zn Phosphate Zinc Oxide Complex in Peroxide Cross-linked EVA/LDPE XL-EVA/LDPE (60/40) blend - total FR loading 65% 24 Rate of Heat Release Rate of Smoke Production m 2 kw/m Zerogen 100SP Z100SP/5% KG 981 1/s Zerogen 100SP Z100SP/5% KG 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%). Improved char formation was not observed at higher MDH replacement levels. LOI UL94 V0 V0

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 Mo 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), Zn 2+ 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%).

26 26 Thank you for your attention! Our contact information: Alex Isarov, David Temples, Mark Herndon J.M. Huber Corporation Fairmount, GA USA