An intumescent flame retardant - expandable graphite: Preparation, characteristics and flame retardance for polyethylene
Keywords:
Borate, expandable graphite, intumescent flame retardant, polyethylene, synergistic efficiencyAbstract
A combined intumescent flame retardant expandable graphite (EG), with an initial expansiontemperature of 155°C and expansion volume of 515 mL g-1, was successfully prepared based ona chemical intercalation method of material graphite under oxidation of KMnO4, intercalationof H2SO4 and Na4B2O7· 10H2O at the mass ratio C : KMnO4 : H2SO4 (98%) : Na 4B2O7· 10H2Oof 1.0 : 0.4 : 5.5 : 0.6 (H2SO4 diluted to a mass concentration of 80-wt. % before reaction),and characterized by expansion volume (EV), initial expansion temperature, X-ray diffraction(XRD). The flame retarding and thermal properties of LLDPE/EG and LLDPE/EG/APPcomposites (LLDPE-Linear low density polyethylene; APP-ammonium polyphosphate) wereinvestigated and characterized by limiting oxygen index (LOI), Fourier transform infraredspectroscopy (FTIR), thermal gravimetric (TG) and differential thermal analysis (DTA). Theresults showed that addition of EG (30-wt. %) increased the LOI of 70LLDPE/30EG compositeto 28.4 %. Even more, the synergistic effect of 20% EG together with 10% APP improvedthe LOI of 70LLDPE/20EG/10APP composite to 30.5%. At the same time, temperaturescorresponding to a 1% weight loss and a maximum weight loss rate increased at about 50°C and2°C, respectively. The 70LLDPE/10APP/20EG composite exhibited higher flame retardancyeven at a lower residual chars than 70LLDPE/30EG specimen. Cohesive and dense charlayer caused by swollen expanded graphite and decomposing products of APP played a moreimportant role in improving thermal stability and flame retardancy than weight of residualcarbon. The intercalated borate was more effectual in improving the flame retardancy than thedirect additive of Na4B2O7· 10H2O.References
Avdeev, V. V., Monyakina, L. A., Nikol'skaya, I. V., Sorokina, N. E. & Semenenko,
K. N. 1992a. The choice of oxidizers for graphite hydrogenosulfate chemical
synthesis. Carbon 30(6): 819-823.
Avdeev, V. V., Monyakina, L. A., Nikol'skaya, I. V., Sorokina, N. E., Semenenko, K.
N. & Finaenov, A. I. 1992b. Chemical synthesis of graphite hydrogenosulfate:
calorimetry and potentiometry studies. Carbon 30(6): 825-827.
Bian, X. C., Tang, J. H., Li, Z. M., Lu, Z. Y. & Lu, A. 2007. Dependence of flameretardant
properties on density of expandable graphite filled rigid polyurethane
foam. Journal of Applied Polymer Science 104(5): 3347-3355.
Duquesne, S., Delobel, R., Bras, M. L. & Gamino, G. 2002. A comparative study of
the mechanism of action of ammonium polyphosphate and expandable graphite
Xiu-Yan Pang, Ming-Wei Duan, Zhi-Xiao Zhai and Tian Yu
in polyurethane. Polymer Degradation and Stability 77(2): 333-334.
Gao, Z. H., Zhang, Y., Song, P. G., Cai, Y. Z., Guo, Q., Fang, Z. P. & Peng, M.
A novel zinc chelate complex containing both phosphorus and nitrogen
for improving the flame retardancy of low density polyethylene. Journal of
Analytical and Applied Pyrolysis 92(2): 339-346.
Genovese, A. & Shanks, R. A. 2007. Structural and thermal interpretation of the
synergy and interactions between the fire retardants magnesium hydroxide and
zinc borate. Polymer Degradation and Stability 92(1): 2-13.
Han, Z. D., Wu, Z., Shan, L. W., Ma, C. G. & Zhang, X. Y. 2012. Study on
intumescent flame retarded polyethylene. China Plastics 26(2): 50-54.
Kuan, C. F., Tsai, K. C., Chen, C. H., Kuan, H. C., Liu, T. Y. & Chiang, C. L.
Preparation of expandable graphite via H2O2-hydrothermal process
and its effect on properties of high-density polyethylene composites. Polymer
Composites 33(6): 872-880
Li, R. C. 1993. Manufacturing method of expandable graphite. CN 1068152A.
Li, S. L., Long, B. H., Wang, Z. C., Tian, Y. M., Zheng, Y. M. & Zhang, Q. 2010.
Synthesis of hydrophobic zinc borate nanoflakes and its effect on flame retardant
properties of polyethylene. Journal of Solid State Chemistry 183(4): 957-962.
Liu, S. J., Meng, Q. L., Ma, M. M., Dong, X. X. & Chi, W. D. 2011. Preparation
and application of B-P-Zn-Si density board flame retardant preservative. CN
A.
Liu, S., Zang, C. G. & Jiao, Q. J. 2007. Expandable graphite-filled polymer
(LDPE) composite film materials for flame retardancy. Journal of Safety and
Environment 7(4): 111-114.
Lu, Y. B., Zhang, Y. J. & Xu, W. J. 2011. Flame retardancy and mechanical
properties of ethylene-vinyl acetate rubber with expandable graphite/ammonium
polyphosphate/dipentaerythritol system. Journal of Macromolecular Science,
Part B: Physics 50(10):1864-1872.
Mahapatra, S. S. & Karak, N. 2007. s-Triazine containing flame retard ant
hyperbranched polyamines: Synthesis, characterization and properties
evaluation. Polymer Degradation and Stability 92(6): 947-955.
Menachem, L. 2001. Synergism and catalysis in flame retardancy of polymers.
Polymers for Advanced Technologies 12(3-4): 215-222.
Modesti, M. & Lorenzetti, A. 2002a. Flame retardancy of polyisocyanurate–
polyurethane foams: use of different charring agents. Polymer Degradation and
Stability 78(2): 341-347.
Modesti, M. & Lorenzetti, A. 2002b. Halogen-free flame retardants for polymeric
foams. Polymer Degradation and Stability 78(1): 167-173.
An intumescent flame retardant - expandable graphite: Preparation, characteristics and flame retardance for polyethylene 15
Modesti, M. & Lorenzetti, A. 2003. Improvement on fire behavior of water blown
PIR–PUR foams: use of an halogen-free flame retardant. European Polymer
Journal 39(2): 263-268.
Modesti, M., Lorenzetti, A., Simioni, F. & Camino, G. 2002. Expandable graphite
as an intumescent fl ame retardant in polyisocyanurate–polyurethane foams.
Polymer Degradation and Stability 77(2): 195-202.
Pang, X. Y., Song, M. K., Tian, Y. & Duan, M. W. 2012. Preparation of high
dilatability expandable graphite and its anti-flame property for LLDPE. Journal
of the Chilean Chemical Society 57(3): 1318-1322.
Pang, X. Y., Zhi, S. K., Su, Y. J., Liu, L. & Lin, F. 2011. A method for preparing
expandable graphite with high initial expansion temperature and high dilatability.
Journal of HeiBei University (Natural Science Edition) 31(5): 497-501.
Ramazani, S. A. A., Rahimi, A., Frounchi, M. & Radman, S. 2008. Investigation
of flame retardancy and physical–mechanical properties of zinc borate and
aluminum hydroxide propylene composites. Materials & Design 29(5): 1051-
Shi, L., Li, Z. M., Xie, B. H., Wang, J. H., Tian, R. C & Yang, M. B. 2006. Flame
retardancy of different-sized expan dable graphite particles for high-density rigid
polyurethane foams. Polymer International 55(8): 862-871.
Thirumal, M., Khastgir, D. & Singha, N. K . 2008. Effect of expandable graphite
on the prop erties of intumescent flame-retardant polyurethane foam. Journal of
Applied Polymer Science 110(5): 2586-2594.
Wang, L., Song, K. M., Zhang, S. H., Li, Q., Li, Y. P. & Liu, M. 2009. Study
on preparation of the high expansion volume and low temperature expandable
graphite. Bulletin of the Chinese Ceramic Society 28(4): 844-849.
Wang, Z. Z., Hu, Y., Gui, Z. & Zong, R. W. 2003. Halogen-free flame retardation
and silane crosslinking of polyethylenes. Polymer Testing 22(5): 533-538.
Wu, Z. P., Hu, Y. C., Chen, M. Q. & Shu, W. G. 2008. Effects of ultra-fine zinc borate
on the thermal stability of LDPE/IFR system. Plastics Science and Technology
(Chinese) 36(11): 86-89.
Xie, R. C. & Qu, B. 2001a. Expandable graphite systems for halogen-free flameretarding
of polyolefins. Journal of Applied Polymer Science 80(8): 1190-1197.
Xie, R. C. & Qu, B. 2001b. Synergistic effects of expandable graphite with some
halogen-free flame retardants in polyolefin blends. Polymer Degradation and
Stability 71(3): 375-380.
Xue, E. Y. & Zeng, M. X. 1988. Flame retardant science and application. National
defense industrial press, Beijing.
Xiu-Yan Pang, Ming-Wei Duan, Zhi-Xiao Zhai and Tian Yu
Xue, M. L., Yu, Y. L., Ren, Z. H. & Zhang, J. S. 2002. Improvement in electrochemical
synthesis of expanded graphite. Fine Chemistry 19(10): 567-570.
Yan, A. H., Zhou, Z. Q. & Wu, Z. 2006. Study on synergistic flame-retarding
performance of polythene modified with expandable graphite and ammonium
polyphosphate. Chemical Engineer 126(3): 48-50.
Ye, L., Meng, X. Y., Ji, X., Li Z. M. & Tang, J. H. 2009. Synthesis and characterization
of expandable graphite–poly(methyl methacrylate) composite particles and
their application to flame retardation of rigid polyurethane foams. Polymer
Degradation and Stability 94(6): 971-979.
Zhang, P., Song, L., Lu, H. D., Wang, J. & Hu, Y. 2010. The influence of expanded
graphite on thermal properties for paraffin/high density polyethylene/chlorinated
paraffin/antimony trioxide as a flame retardant phase change material. Energy
Conversion and Management 51(12): 2733-2737.
Zhu, H. F., Zhu, Q. L., Li, J., Tao, K., Xue, L. X. & Yan, Q. 2011. Synergistic effect
between expandable graphite and ammonium polyphosphate on flame retarded
polylactide. Polymer Degradation and Stability 96(2): 183-189.
Zhu, Z. P., Chen, Z. Y. & Han, D. H. 1998. Chemical preparation of expansible
graphite by KMnO4 - H2O2 oxidation method. Journal of Hefei University of
Technology (Nat. Sci. Ed.) 21(1): 131-134.
