Permanent magnets made by the sintering process are hard and brittle. For this very
reason, they are not suitable for all applications. In applications where the use of
such magnets is not possible, we can use bonded magnets. They consist of
magnetic powders whose particles are bound by a special binder, such as various
resins, rubbers or polymers.
As part of the diploma work, we prepared a plastic magnetic material based on the
magnetic powder of strontium hexaferrite (SrFe12O19) with a polyphenylene sulphide
(PPS) as a binder, to which we added a liquid crystalline polymer (LCP). We were
interested to see the effect of the latter on the density, magnetic and mechanical
properties. We prepared a premix of magnetic powder with additives and a polymer
premix of both polymers. The prepared premixes were converted into composite
granules using extrusion technology, which were later dried. Injection molding was
used to convert the dried granules into samples that were used as part of a research
method. First, the density was measured using magnetic cylindrical samples and the
main magnetic properties of the material were determined using magnetization and
demagnetization. A three-point bending test was performed on the test specimens in
the form of test tubes to determine the bending properties, followed by a tensile test,
used to determine the strength and forming properties. The measurement results of
the prepared material were compared with the same material without the addition of
liquid crystalline polymer.
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