Recently, high performance of noise suppression materials heve been required to suppress the electromagnetic noise generated from high frequencies of circuits and chips in electronic equipment. These are usually supplied as a sheet of filler composite consisting of magnetic powder and polymeric binder. High packing of soft magnetic powder within the sheet produces a significant suppression of electromagnetic noise. Therefore, silane was applied to magnetic powder with various kinds of silanes such as ionic, amino, methacrylic, vinyl, and epoxy silanes to increase packing of the filler within the binder. The packing was evaluated from the void calculated by specific gravity of the magnetic filler composite sheet. All silanes have lowered the void in the composite. This effect increases in the following order; epoxy, vinyl, methacrylic, amino, and ionic silanes. This means that ionic property of silane gives affinity to the binder. As a result, the magnetic permeability increases with specific gravity of the filler composite modified by the treatment with various kinds of silanes. Finally, the occurrence of the void was examined from the torque values of a twin axis mixing mill and also observed from a soft X ray image. The resulting value of the torque in the milling is not dependent on the kinds of silanes used in treating the filler. This means that the size of the void arises not from the mechanical process of milling, but mainly from the surface treatment with silane. In the observation of voids by the X-ray imaging, there are not only a lot of voids but also aggregates of the filler in a sheet of filler composites without surface treatment. Silane treatment significantly reduces voids and aggregates. In conclusion, silane treatment plays an important role on the homogeneous spread of the filler into the polymeric binder.

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In order to clarify the relationship between the material properties of metal injection molding (MIM) parts and MIM processability, melt shear viscosity and Pressure-Volume-Temperature (PVT) measurements were performed for various MIM materials with different blend ratios of metal powder to polymer binder. The changes in internal cavity pressure for these blends were monitored and the appearance of molded parts were evaluated. The following results were obtained. The pellet density of MIM material increased monotonously with an increase in metal powder; however, above 70vol%, a reduction in density was observed as there was insufficient binder to enclose all the metal powder and voids appeared inside the pellets. The melt shear viscosity increased with increasing metal powder content, with an abrupt increase at 50vol%. PVT measurements showed a two-step decrease in specific volume, a result of the solidification of the polymeric binder (POM, PP, WAX, etc.). The internal cavity pressure for the MIM materials differed from the binder resins, and a two-step pressure decrease was also observed, showing similarities to the PVT data. Pressure energy, defined as the area under the internal cavity pressure vs time curve, was studied during the MIM cooling process. At 60vol% or less, the maximum internal cavity pressure and the holding pressure were nearly the same. The solidification rate increased with increasing metal powder content, with an abrupt increase at 65vol%. Furthermore, at 65vol% and over, cracks occurred in MIM products. These combined results indicated that the optimum MIM blend was 60vol% metal powder.

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