The manufacturing process for carbon fiber precursor filaments is a complex and intricate procedure that directly determines the performance and quality of the final carbon fiber product.
Raw Material Preparation
The primary raw material for carbon fiber precursor filaments is acrylonitrile monomer; additionally, comonomers (such as itaconic acid, methyl acrylate, etc.) must be incorporated to enhance the fiber's properties. During the raw material preparation phase, the acrylonitrile monomer undergoes purification to remove impurities and moisture, thereby ensuring the purity of the feedstock. Concurrently, based on production requirements, the various monomers and additives are precisely weighed and pre-mixed to prepare for the subsequent polymerization reaction.
Polymerization
Polymerization is the core step in the production of carbon fiber precursor filaments. During this stage, pre-mixed monomers and additives are introduced into a polymerization reactor; under the influence of a catalyst, a free-radical polymerization reaction takes place to produce polyacrylonitrile (PAN) polymer. The conditions of the polymerization reaction-such as temperature, pressure, and reaction time-have a significant impact on the polymer's molecular weight, molecular weight distribution, and structure. Therefore, reaction conditions must be strictly controlled to ensure the stability of the polymer's properties.
Spinning
Spinning is the critical step in converting the polyacrylonitrile polymer into fibers. The primary spinning methods employed are wet spinning and dry spinning. In wet spinning, the polymer solution is extruded through a spinneret into a coagulation bath; the solvent within the solution rapidly diffuses into the bath, causing the polymer to solidify into fibers. In dry spinning, the polymer solution is extruded through a spinneret into a stream of hot air; the solvent evaporates, and the polymer solidifies into fibers. During the spinning process, parameters such as the shape and size of the spinneret orifices, as well as the spinning speed, must be carefully controlled to obtain fibers with the desired cross-sectional shape and dimensions.
Post-processing
Post-processing constitutes the final stage in the production of carbon fiber precursor filaments, comprising steps such as washing, stretching, drying, and winding. Washing serves to remove residual solvents and impurities from the fiber surface; stretching is performed to enhance the fiber's orientation and crystallinity, thereby improving its mechanical properties; drying eliminates moisture from the fibers to prevent mildew formation during storage; and winding involves spooling the dried fibers onto bobbins to facilitate subsequent processing and utilization.
