Magnetic memory effect in magnetite charged polypropylene composite

Abstract

The behaviour of damping and dynamic shear modulus in polypropylene charged with either different volume fraction or size of magnetite (Fe3O4) particles, as a function of the applied magnetic field at 318, 353 and 403 K; has been studied. An increase of the alternating magnetic field oscillating with 50 Hz, leads to an increase of the damping. In addition, during the subsequently decreasing alternating magnetic field, the damping decreases, but a hysteretic behaviour appeared. The behaviour of the damping and the elastic modulus under the application of an alternating magnetic field was explained by the development of a magnetic fatigue damage occurring around the particle interface due to oscillation of magnetite particles. In contrast, during the increase of a direct magnetic field, the damping decreases and the elastic modulus increases. Measurements performed at 353 and 403 K allowed observing the interaction process among the particles of magnetite in the polymer matrix. After the decrease in the direct magnetic field, from the maximum reached value, damping and modulus remain smaller and higher, respectively; giving rise to a memory effect. In addition, a mesoscopic description of magnetite filled polymer composite materials has been performed in the continuous media by considering the interaction between magnetic and mechanical forces. Theoretical predictions of here developed model were qualitatively applied with good success for explaining the memory effect in magnetite filled polypropylene under the application of a direct magnetic field.