ABSTRACT Compounds of poly(ethylene-co-vinyl acetate) (EVA with vinyl acetate content 33%) with three different organic per- oxides, namely, dialkyl peroxide, peroxyester peroxide, and peroxyketal peroxide, were prepared with a twin screws extruder and a two-roll mixing mill. The cure behavior of the EVA compounds was analyzed from rheographs, which were obtained by a moving die rheometer (MDR) at various curing temperatures between 150?C to 170?C. The effects of organic peroxides on cure behavior were examined. The dynamic curing obtained by the torque rheometer provided sufficient experimental data to show that dialkyl peroxide is not suitable because it has a high half-life temperature and its by-products can discolor the final product. Peroxyester peroxide is good for curing at temperatures in the range of 150?C to 160?C, which accomplished an ultimate cure within 5 to 8 minutes. Also, the peroxyketal peroxide has higher performance, which decreased the optimum cure time to 3 minutes. The thermal decomposition mechanism of organic peroxide was applied to explain how the cure behavior is affected by generated free radicals.
Cite this paper
K. Thaworn, P. Buahom and S. Areerat, "Effects of Organic Peroxides on the Curing Behavior of EVA Encapsulant Resin," Open Journal of Polymer Chemistry, Vol. 2 No. 2, 2012, pp. 77-85. doi: 10.4236/ojpchem.2012.22010.
 P. Galli and G. Vecellio, “Polyolefins: The Most Promising Large-Volume Materials for the 21st Century,” Journal of Polymer Science Part A: Polymer Chemistry, Vol. 42, No. 3, 2004, pp. 396-415. doi:10.1002/pola.10804
 A. El Amrani, A. Mahrane, F. Y. Moussa and Y. Bouken- nous, “Solar Module Fabrication,” International Journal of Photoenergy, Vol. 2007, Article ID 27610.
 A. W. Czanderna and F. J. Pern, “Encapsulation of PV Modules Using Ethylene Vinyl Acetate Copolymer as a Pottant: A Critical Review,” Solar Energy Materials and Solar Cells, Vol. 43, No. 2, 1996, pp. 101-181.
 J. H. Wohlgemuth and R. C. Petersen, “Solarex Experi- ence with Ethylene Vinyl Acetate Encapsulation,” Solar Cells, Vol. 30, No. 1, 1991, pp. 383-387.
 K. J. Lewis, “Encapsulant Material Requirements for Photovoltaic Modules,” In: C. G. Geblein, D. J. Williams, and R. D. Deanin, Eds., Polymers in Solar Energy Utili- sation, American Chemical Society (ACS), Washington DC, 1983, pp. 367-385. doi:10.1021/bk-1983-0220.ch023
 E. F. Cuddihy, D. R. Burger, P. Willis, B. Baum, A. Gar- cia and C. Minning, “Polymer Encapsulation Materials for Low-Cost Terrestrial Photovoltaic Modules,” In: C. G. Geblein, D. J. Williams, and R. D. Deanin, Eds., Poly- mers in Solar Energy Utilisation, American Chemical Society (ACS), Washington DC, 1983, pp. 353-366.
 J. P. Galica and N. Sherman, “Results to Date-Develop- ment of New EVA-Based Encapsulants, Faster-Curing and Flame Retardant Types,” Conference Record of the 28th IEEE Photovoltaic Specialists Conference, Anchor- age, 15-22 September 2000, pp. 30-35.
 S. P. Shea and J. H. Wohlgemuth, “Improvements to Polycrystalline Silicon PV Module Manufacturing Tech- nology,” Conference Record of the 29th IEEE Photo- voltaic Specialists Conference, New Orleans, 19-24 May 2002, pp. 227-230. doi:10.1109/PVSC.2002.1190497
 P. Klemchuk, M. Ezrin, G. Lavigne, W. Holley, J. Galica and S. Agro, “Investigation of the Degradation and Stabi- lization of EVA-Based Encapsulant in Field-Aged Solar Energy Modules,” Polymer Degradation and Stability, Vol. 55, No. 3, 1997, p. 347.
 M. Narkis and J. Miltz, “Peroxide Crosslinking of Ethyl- ene-Vinyl Acetate Copolymer,” Journal of Applied Polymer Science, Vol. 21, No. 3, 1977, pp. 703-709.
 S. Mishra, B. Baweja and R. Chandra, “Studies on Dy- namic and Static Crosslinking of Ethylene Vinyl Acetate and Ethylene Propylene Diene Tercopolymer Blends,” Journal of Applied Polymer Science, Vol. 74, No. 11, 1999, pp. 2756-2763.
 Y. T. Sung, C. K. Kum, H. S. Lee, J. S. Kim, H. G. Yoon and W. N. Kim, “Effect of Viscosity Ratio and Acetate Copolymer,” Polymer, Vol. 46, No. 25, 2005, pp. 11844- 11848. doi:10.1016/j.polymer.2005.09.080
 H. J. Tai, “Molecular Structure Evolution in Peroxide- Initiated Crosslinking of an Ethylene Vinyl Acetate Copolymer and a Metallocene Polyolefin Elastomer,” Polymer Engineering & Science, Vol. 39, No. 9, 1999, pp. 1577-1583. doi:10.1002/pen.11551
 H. A. Khonakdar, S. H. Jafari, A. Haghighi-Asl, U. Wagenknecht, L. Haussler and U. Reuter, “Thermal and Mechanical Properties of Uncrosslinked and Chemically Crosslinked Polyethylene/Ethylene Vinyl Acetate Copolymer Blends,” Journal of Applied Polymer Science, Vol. 103, No. 5, 2007, pp. 3261-3270.
 A. Thitithammawong, C. Nakason, K. Sahakaro and J. Noordermeer, “Effect of Different Types of Peroxides on Rheological, Mechanical, and Morphological Properties of Thermoplastic Vulcanizates Based on Natural Rubber/ Polypropylene Blends,” Polymer Testing, Vol. 26, No. 4, 2007, pp. 537-546.
 T. Fargere, M. Abdennadher, M. Delmas and B. Boutevin, “Determination of Peroxides and Hydroperoxides with 2,2-diphenyl-1-picrylhydrazyl (DPPH), Application to Ozonized Ethylene Vinyl Acetate Copolymers (EVA),” European Polymer Journal, Vol. 31, No. 5, 1995, pp. 489-497. doi:10.1016/0014-3057(94)00201-0
 J. S. Parent, K. Geramita, S. Ranganathan and R. A. Whitney, “Silane-Modified Poly(ethylene-co-vinyl acetate): Influence of Comonomers on Peroxide-Initiated Vinylsilane Grafting,” Journal of Applied Polymer Science, Vol. 76, No. 8, 2000, pp. 1308-1314.
 J. S. Parent, M. Spencer and R. A. Whitney, “Influence of Hydrogen Donors on Peroxide-Initiated Melt Grafting of Vinylsilane to Poly(ethylene-co-vinyl acetate),” Journal of Applied Polymer Science, Vol. 83, No. 11, 2002, pp. 2397-2402. doi:10.1002/app.10304
 Arkema Inc., “Product Bulletin, Organic Peroxides: General Catalog,” 2006.
 J. S. Dick, R. A. Annicelli, C. Baddorf, K. Baranwal and C. J. Cable, “Rubber Technology: Compounding and Testing for Performance,” 2nd Edition, Hanser Gardner Publications, Ohio, 2009.
 O. Bianchi, J. De N. Martins, R. Fiorio, R. V. B. Oliveira and L. B. Canto, “Changes in Activation Energy and Kinetic Mechanism During EVA Crosslinking,” Polymer Testing, Vol. 30, No. 6, 2011, pp. 616-624.
 P. A. Callais, “Organic Peroxides,” In: A. Tracton, Ed., Coating Technology Handbook, 3rd Edition, CRC Press, New Jersey, 2006.
 M. M. A. Grima, “Novel Co-Agents for Improved Properties in Peroxide Cure of Saturated Elastomers,” Ph.D. Thesis, University of Twente, Enschede, 2007
 F. J. Pern, “Factors That Affect the Eva Encapsulant Discoloration Rate upon Accelerated Exposure,” Solar Energy Materials and Solar Cells, Vol. 41-42, 1996, pp. 587-615. doi:10.1016/0927-0248(95)00128-X
 Y.-F. Lin, C.-P. Lin, L.-Y. Chen, T.-S. Su, J.-M. Tseng, “Effect of Different Concentrations of Acetone for the Decomposition Reactions of Peroxyketal Peroxides,” Thermochimica Acta, Vol. 527, 2012, pp. 27-32.
 F. J. Pern and S. H. Glick, “Thermal Processing of EVA Encapsulants and Effects of Formulation Additives (for Solar Cells),” Conference Record of the 25th IEEE Photo- voltaic Specialists Conference, Washington DC, 13-17 May 1996, pp. 1251-1254.