Processability,hardness,and magnetic properties of rubber ferrite composites containing manganese zinc ferrites

Rubber ferrite composites have the unique advantage of mouldability, which is not easily obtainable using ceramic magnetic materials. The incorporation of mixed ferrites in appropriate weight ratios into the rubber matrix not only modifies the dielectric properties of the composite but also imparts magnetic properties to it. Mixed ferrites belonging to the series of Mn_{(1 -x)}Zn_x Fe₂ O₄ have been synthesised with different values of x in steps of 0·2, using conventional ceramic processing techniques. Rubber ferrite composites were prepared by the incorporation of these pre-characterised polycrystalline Mn_{(1 -x)}Zn_xFe₂ O₄ ceramics into a natural rubber matrix at different loadings according to a specific recipe. The processability of these elastomers was determined by investigating their cure characteristics. The magnetic properties of the ceramic fillers as well as of the rubber ferrite composites were evaluated and the results were correlated. Studies of the magnetic properties of these rubber ferrite composites indicate that the magnetisation increases with loading of the filler without changing the coercive field. The hardness of these composites shows a steady increase with the loading of the magnetic fillers. The evaluation of hardness and magnetic characteristics indicates that composites with optimum magnetisation and almost minimum stiffness can be achieved with a maximum loading of 120 phr of the filler at x=0 4. From the data on the magnetisation of the composites, a simple relationship connecting the magnetisation of the rubber ferrite composite and the filler was formulated. This can be used to synthesise rubber ferrite composites with predetermined magnetic properties.