Effect of Coprecipitated Barium Ferrite on the Cure Characteristics and Dynamic Properties of Natural Rubber–Ferrite Composites Around Percolation Mahmoud Hosseny Moussa Makled, 1 Hirohiko Washiya, 2 Hiroshi Tsuda, 1 Toshiyuki Matsui 3 1 Physics Department, Faculty of Science, Benha University, Benha 13518, Egypt 2 Hyogo Prefectural Institute of Technology, 3-1-12 Yukihira-cho, Suma-ku, Kobe 654-0037, Japan 3 Graduate School of Engineering, Osaka Prefecture University, 1-1Gakuen-Cho, Naka-ku, Sakai 599-8531, Japan Received 8 November 2007; accepted 17 February 2009 DOI 10.1002/app.30263 Published online 7 May 2009 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The influence of coprecipitated hexagonal barium ferrite BaFe 12 O 19 phase on the cure characteris- tics and dynamic properties of natural rubber–ferrite composites has been studied as a function of ferrite loading up to 220 phr (part per hundred part of rub- ber). Unusual characteristics of coprecipitated ferrite par- ticles were discovered by scanning electron microscope. The results show that scorch time t 10 and cure time t 90 decrease dramatically with increasing ferrite content up to critical ferrite loading. After 160 phr, t 90 increases sharply with increasing ferrite content, in contrast to sat- uration of t 10 . Minimum torque recorded normal behav- ior at low ferrite loading, whereas it decreases with increasing ferrite content at high ferrite loading because of dilution effects. The storage modulus E 0 and loss modulus E 00 decrease with increasing temperature. The loss tangents (tand) of the composites are greater than those of the pure rubber. Linear viscoelastic behavior was observed as a result of the homogeneity and com- patibility of the composites. V V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 3294–3299, 2009 Key words: rubber ferrite composites; dynamic properties; cure characteristics; barium ferrite INTRODUCTION Hard ferrite or ceramic permanent magnets are con- sidered to be an important and sophisticated class of engineering materials, which are used extensively in various applications. Hexaferrite magnets have found acceptance in many electronic products, as a result of their superior cost efficiency, large coerciv- ity, and specific magnetic saturation associated with their high magnetic and chemical stability. 1,2 Many sintered magnets are brittle, hard, and difficult to machine to their final form. The advantages of poly- mer-bonded magnets over their metallic and ceramic counterparts include low weight, resistance to corro- sion, ease of machining and forming, and capability for high production rates. 3 The evaluation of the cure characteristics and dynamic properties helps to understand the process- ability and also provides valuable information about the matrix–filler interaction, percolation threshold, and filler dispersion. These essential characteristics play an important role in determining the overall physical properties of the composites. Furthermore, the filler parameters influence the dynamic and the physical properties of the composites in different ways. 4 For example, (i) particle–particle interactions become important above certain volume fractions, depending on the particle morphology. 5,6 (ii) The percolation limit can be achieved at different filler loadings, depending on the aspect ratio and the par- ticle size of the fillers. 7,8 (iii) Filler aggregation, espe- cially at high loading, leads to chain-like filler structure or clusters, which affect rubber properties and viscoelastic behavior. 4 (iv) Filler increases the thermal conductivity of the composite matrix, conse- quently reducing the cure time for thick rubber articles and giving uniform curing throughout the material. 9 In other words, the dynamic properties of rubber products are influenced by many factors, such as the size, shape, nature, and state of distribu- tion of filler; type of rubber; adhesion and thermal compatibility of the matrix; and so forth. 10,11 Thus, the overall effect of each of the variables on the final properties of the composites is complex. A few researchers have reported the processing and dynamic properties of polymer composites con- taining hexaferrite prepared by ordinary powdered methods up to ferrite loading of 120 phr (part per hundred part of rubber). The result indicates poor adhesion between ferrite particles and polymer, de- spite the fact that the percolation threshold was not Journal of Applied Polymer Science, Vol. 113, 3294–3299 (2009) V V C 2009 Wiley Periodicals, Inc. Correspondence to: M. H. M. Makled (makledmahmoud@ yahoo.com).