Synthesis and characterization of rubber-ferrite composites

Abstract

Rubber ferrite composites (RFCs) based on Nitrile butadiene rubber (NBR) as a host matrix and Co-Zn ferrite as a filler were investigated in the present work. Co-Zn ferrite was prepared by Sol-Gel citrate method and the cubic spinel structure was confirmed by X-ray. The lattice parameter, crystallite size and surface area calculations were performed. The results were divided into three groups: Group I (Composition effect): Co1-xZnxFe2O4 (x=0, 0.2, 0.4, 0.6, 0.8, 0.9, 0.95 and 1) series was added to rubber matrix with constant load, 4 phr. Rheometric characteristics showed that maximum torque and cure rate index (CRI) increased up to Zn-concentration x=0.8 then decreased while the cure time tc90 showed the inverse behavior. On the other hand, hardness and mechanical parameters which include stress at yield σB, stress at rupture σR and Young’s modulus E increased with Zn-concentration up to x=0.8 then decreased. AC resistivity ρac, real part ε' and imaginary part '' of dielectric constant showed a decreasing behavior with frequency. On the other hand, ρac decreased with Zn-concentration x while ' and '' increased. According to results obtained from Group I, the composition (Co0.2Zn0.8Fe2O4) is found to have the optimum values in mechanical parameters. So Group II was based on studying the effect of adding this composition with different loads to rubber matrix. Abstract 2 Group II (load effect): Co0.2Zn0.8Fe2O4 was added with loads (2, 4, 6, 8, 10, 12, 14, 20, 25 and 30 phr). Again, rheometric characteristics showed that maximum torque and cure rate index (CRI) increased up to load=20 phr then decreased while cure time tc90 showed the inverse behavior. Mechanical parameters (stress at yield σB, stress at rupture σR and Young’s modulus E) increased up to load=20 phr then decreased while hardness showed a continuous increase. Electric resistivity ρac decreased with load while ' and '' increased. According to results obtained from Group II, most of the properties were enhanced at load=20 phr. So, Group III was based on studying the effect of adding composition x=0.8 with load=20 phr but with different particle sizes to rubber matrix. Group III (particle size effect): Co0.2Zn0.8Fe2O4 was annealed at 400oC, 600oC and 800oC for 2 hours to obtain different particle sizes. The obtained samples were added to rubber matrix with load 20 phr. Rheometric characteristics showed that maximum torque and cure rate index (CRI) decreased with particle size while the cure time tc90 has an inverse behavior. Mechanical parameters (stress at yield σB, stress at rupture σR, Young’s modulus E) and hardness decreased with particle size. On the other hand, ρac decreased with particle size while ' and '' increased. Smaller particle size seems to give the best properties.