| The continuous expansion of carbon fiber applications had led to increasingly fierce competition.Reducing the cost of CARBON FIBER was a powerful way to increase competitiveness.The preoxidation process was a key process of manufacturing CARBON FIBER,which took a lot of time and energy.It was a technical demand in this situation to study and innovate a new preoxidation technology to reduce the costs.In this paper,various characterization methods and indicators were used to analyze HS-PC,including elements analysis(EA),Fourier transform infrared spectroscopy(FT-IR),skin-core structure testing,density,crystallinity,break temperature,etc.On the basic study of the online pre-oxidation process,an innovative and efficient preoxidation process was designed to reduce the production cost of CARBON FIBER,which using a way of reducing preoxidation temperature zone.Additionally,under the theoretical guidance of laboratory research and pilot line,we effectively converted laboratory research results into industrial effects on industrial production line,achieving the reduction of product cost on the premise of ensuring carbon fiber performance.Research indicates:1.HS-PC has its own characteristics in terms of polymerization ratio,spinning process,and mechanical properties.The phenomenon of concentrated heat released in the preoxidation procedure is obvious,which should be taken into consideration in designing preoxidation gradient temperature.The increase of fiber tow leads to a decrease in break temperature in preoxidation procedure,which needs to be considered as key concerns in the design and adjustment of preoxidation parameters.2.Research on pilot line shows that the increase of temperature and residence time promote the rate of the preoxidation reaction,which is manifested in the increase of oxygen content,density,degree of cyclization and the evolution of fiber skin-core structure.The increasing of circulating air speed has a positive effect on preoxidation reaction,but the impact is smaller than temperature and time.As the tension increases,the break temperature tends to decrease.3.The current preoxidation process uses a six-stage gradient preoxidation temperature,during which the fiber internal structure changes to a heat-resistant trapezoidal structure and the corresponding fiber coloralso appears.Beige-golden-brown-burgundy-black changes regularly.With the heating process,the fiber skin-core structure is become obvious gradually,and the thickness of the skin layer increases,and also the degree of cyclization,break temperature.Through the comparative analysis of the process and product results,the online process has adjustable space for further optimization.4.The high-efficiency technology adopts a four-stage gradient preoxidation temperature method.During the heating process,the changes of physical and chemical indicators such as elements,functional groups,skin-core structure,degree of cyclization,and density of PAN fiber are consistent with the online six-stage gradient temperature process;However,due to the design of a higher initial temperature,the skin-core structure appears earlier,and the fiber color changes significantly.Choosing a reasonable technology with four-zone preoxidation temperature can effectively ensure that the indicators characterizing the PAN pre-oxidation fiber are suitable,and carbon fibers with excellent mechanical properties are prepared.5.From gradient six-stage preoxidation temperature(200℃-220℃-234℃-243℃-254℃-263℃)rise to the gradient four-stage temperature(226℃-241℃-254℃-266℃),the operation condition in industrial production line is well.After fine-adjusting,the mechanical properties of CARBON FIBER under the new preoxidation technology are equivalent to online process(tensile strength is 4082MPa,tensile modulus is 240GPa,linear density is 790g/km).And about 6%of the product cost decreases. |
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