Injection molding of magneto-sensitive polymer composites

Magneto sensitive parts made of a thermoplastic elastomer reinforced with iron microparticles were prepared by imposing a magnetic field during injection molding. In particular, an aluminum mold was designed to host an electro-magnet able to apply a magnetic field during the injection of the material into the mold and its subsequent solidification. Samples obtained in the presence of magnetic field were characterized by a peculiar, aligned distribution of iron particles along the magnetic field lines, and columnar structures of variable length were obtained. The mechanical characterization showed that the samples in which the iron particles were aligned had higher modulus compared to samples in which the particles were randomly dispersed. The magnetic field induced an anisotropic structural reinforcement that imparted to composite samples a magnetostrictive feature, namely the capability to sense the magnetic field and to react with a shape change under the application of the magnetic field.