| dc.description.abstract | Conductive polymer composite material is increasingly used in a variety of fields, and its related processing technology has been a focus of research and development. Regarding magnetic fiber, because the orientation and distribution of the fiber affect the electrical and mechanical properties of products, the control of fiber orientation and distribution has been regarded as a critical technology. This study used magnetic-assisted injection molding to control the orientation of magnetic fibers during the melt-polymer filling process. This study can be divided into two parts. In first part, a special mold containing a magnetic apparatus was simulated and designed. Its material and thickness of various spacing blocks as well as the optimal layout of magnets in the mold were determined. An actual mold with the same magnet layout was then manufactured accordingly, and the measured magnetic flux density was compared with simulated results. This study also examined the coupled effect of magnetic and flow fields on the orientation of nickel-coated carbon fibers, calculating the magnetic moment produced due to the influence of the magnetic field on the fibers when melt polymer flowed through different positions in the cavity during the filling process. The flow trajectories of the fibers, which were affected by the magnetic field, were also predicted.
The second part was experimental procedures. The LDPE was mixed with the nickel-coated carbon to palletize plastic granules for magnetic-assisted injection molding. This study used different process parameters (melt temperature, mold temperature, injection speed, and external magnetic field) to control fiber orientation and distribution. In this study we found that external magnetic field can make the fiber concentrate on the left and right side, and make the fiber orientation parallel to the magnetic field direction. Moreover, altering fiber distribution and orientation affects the electrical conductivity of the products. Therefore, controlling the process parameters can be one way of improving electrical conductivity.
To conclude, the experimental results show that the electrical conductivity was increased along with high mold temperature and high melt temperature under external magnetic field. In addition, the electrical conductivity was slightly increased when the injection speed is raised. | en_US |