| In recent years, with the development of superconducting technology and the development of high-performance magnetic materials, the magnetic effect is applied to the processing of diamagnetic material, which gradually attracts people’s attention. For the introduction of the magnetic field in the injection molding process, and in order to explore the influence of magnetic field on the injection molding process, by means of theoretical analysis and experimental study, this paper has made a deep study on the influence of magnetic field on the polymer materials. The main research contents and work is as follows:(1) Based on the phenomenon that many crystalline polymers can align magnetically and produce ordered organization under appropriate conditions, the model of micro-domain is presented, which is assumed to exist in the melt when crystallization happens, and the rotational orientation mechanism of micro-domain is investigated. In the help of polymer chain conformation statistics, the anisotropic magnetic susceptibility of every chemical bonds in polymer chain is added together. Then we get Cotton-Mouton constant of common polymers by its definition, which reflects the ability of polymers’ alignment in magnetic field. The calculation of Cotton-Mouton constant is significant for the study of the influence of magnetic field on polymers.(2) Based on the theory of electromagnetic thermodynamics, the changed melting point of polymer annealed in the magnetic field is calculated, and the factors affecting the melting point change are investigated. The assumption that preferential mesophase formation and growth lead to polymers’ alignment in magnetic field is proposed. At the same time, based on the assumption of polymer’s approximate second order phase transition and entropy continuity assumption, the change amount of polymer’s glass transition temperature in magnetic field is derived.(3) By the approach of experimental study, changes in the polypropylene sample, which is annealed in the rotating magnetic field, such as crystalline morphology, melting point, crystallinity, and orientation characterization are investigated. During the process, modern analytical instrument of polarize microscopy, X-r ay diffraction, DSC differential thermal analysis, infrared spectroscopy are used. It is found that the melting point and crystallinity of polypropylene with the presence of rotating magnetic field decreases with the strength of magnetic field, but the degree of orientation increases. (4) The effect of magnetic field generated by the permanent magnet material on polypropylene melt viscosity is investigated by the capillary rheometer. It is found that melt viscosity reduces at a certain temperature with the magnetic field direction perpendicular to the melt flow, and increases with the magnetic field direction parallel to the melt flow. The two-way analysis result of viscosity value’s variance (ANOVA) shows that there is significant difference between the viscosity value measured with magnetic field and without magnetic field. |
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