The Regulation Of The Crystalline Structure Of Pan Polymer And Its Improvement To The Thermal Behavior Of Pre-Oxidation

The preparation process of PAN based carbon fibers contains the preparation process of precursor, the process of pre-oxidation and the process of carbonization. The three processes are time-consuming, but the pre oxidation process is the main reason of time-consuming. We can learn from the research of scholars at home and abroad that the process of pre-oxidation contains cyclization reaction and oxidation reaction. Both of the reactions are accompanied by a lot of heat quantity. If the speed of the pre-oxidation process is too fast, it will lead to severe pre-oxidation process, which is accompanied by a lot of heat quantity. And at the early stage of pre-oxidation, heat-resistant structural of peroxided fibers has not yet generated completely, which makes it easily blow in the pre-oxidation exothermic process, which makes the mechanical properties of carbon fiber get decreased greatly. This is mainly because the pre-oxidation process of PAN polymer getting from the existing spinning process, the reaction temperature sensitivity is too concentrated. It concentrates on a few points on the exothermic temperature, which directly hinders the improvement process of pre-oxidation of PAN polymer. So it is very important to widen the reaction temperature of PAN polymer in the process of pre-oxidation.We can learn from the literature that the influence factors of the process of pre-oxidation of PAN polymer mainly contains crystalline structure, orientation structure, pore structure and layered structure. But the crystalline structure and orientation structure are the main factors that influence the exothermic behavior of PAN polymer. The small grain size and low orientation structure of PAN polymer can make the heat temperature of pre-oxidation process of PAN polymer move to the lower temperature area. Therefore, through the adjustment of spinning process, we should get PAN polymer of small grain size and low degree of orientation meeting the conditions.Through the related research found that the effect of control routine of spinning process of PAN polymer distribution of crystalline structure of co.. So there is a certain difficulty to study the effect of PAN polymer crystalline structure on the thermal behavior of the pre-oxidation. But through different coagulation bath, there may have significant differences in the crystalline structure of PAN polymer.In order to establish the relationship between PAN polymer crystalline structure and thermal behavior of pre-oxidation, this paper tests the crystalline structure of PAN polymer with different structure by controlling the coagulation of different polarity by XRD, and obtains the thermal behavior of the pre-oxidation process by DSC. It has certain guiding significance on improving the spinning process, broadening the pre-oxidation temperature range.And the results show that:1、The polarity of the precipitation agent has significant influence on the crystalline structure of PAN polymer crystal. Because of the coordination force between different precipitant and PAN molecules is different, the ability of PAN molecular chain in crystal nucleation is different, resulting in different crystalline structure of PAN polymer. The polarity of precipitating agent is small, crystallinity, grain size is large, the grain size distribution is wide.2、The force field can influence the crystal orientation structure of PAN polymer, thus affecting the distribution of grain size, but does not change the distribution results of coagulation bath polarity of the grain size of PAN polymer.3、PAN polymer grain size distribution is conducive to broaden the width of the exothermic reaction temperature of the pre-oxidation process, and when the crystal orientation of PAN polymer reduces gradually, the change of the exothermic reaction temperature with the change of grain size distribution becomes slowly.