Pre-Oxidized PAN Fiber Processing for High-Modulus Carbon Fiber
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Solution Overview
Problem
Current methods struggle to produce carbon fibers with high strength and elasticity suitable for advanced composite materials, as increasing elastic modulus leads to brittleness and decreased elongation, making it difficult to achieve high performance carbon fibers with stable physical properties.
Innovation Solution
A method involving a modified pre-oxidation and carbonization process for polyacrylic precursor fibers, including shrinking at 220-260°C, initial drawing in an oxidizing atmosphere, and subsequent pre-oxidation treatment to produce a pre-oxidation fiber with specific density and cyclization conditions, followed by carbonization, to achieve high tensile strength and elastic modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the elastic modulus of carbon fiber is increased to achieve higher performance, then the strength and lightness requirements are met, but the elongation decreases and brittleness increases
Solution Approach 1:
The patent applies preliminary action by conducting a pre-oxidation treatment at 200-280°C before the main carbonization process. This preliminary oxidation step modifies the precursor fiber structure in advance, creating a more stable intermediate state that prevents excessive brittleness during subsequent high-temperature carbonization, thereby maintaining elongation while achieving high elastic modulus and strength
Solution Approach 2:
The patent employs parameter changes by precisely controlling the pre-oxidation temperature (200-280°C) and the oxidation atmosphere conditions. By adjusting these parameters, the oxidation degree is optimized to create the right balance between crystallinity (for high elastic modulus) and structural flexibility (for maintaining elongation), resolving the contradiction between strength and brittleness
2Adaptability or versatility
If conventional pre-oxidation and carbonization methods are used, then carbon fiber is produced, but it is difficult to achieve both high elasticity and high strength with stable physical properties
Solution Approach 1:
The pre-oxidation step serves as a preliminary action that prepares the precursor fiber by controlled oxidation before carbonization. This intermediate treatment establishes a stable structural foundation with appropriate crystallinity and orientation, ensuring that the final carbon fiber achieves both high composite performance and stable physical properties regardless of variations in subsequent processing
Solution Approach 2:
By changing the oxidation parameters (temperature range 200-280°C, atmosphere control) and monitoring the oxidation degree, the patent creates a reproducible intermediate state. This parameter control ensures that the pre-oxidation fiber consistently produces carbon fibers with stable physical properties and high composite performance across different production batches
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in carbon fibers with tensile strength of 5880 MPa or more and elastic modulus of 308 GPa or more, enabling the production of composite materials with superior performance for aerospace and automotive applications.
Implementation Method 1
shrinking the precursor fiber as a pretreatment of pre-oxidation at a load of 0.57 cN/tex (0.58 g/tex) or less in the temperature range of 220 to 260°C
Implementation Method 2
initially-drawing the precursor fiber at a load of 2.6 to 3.4 cN/tex (2.7 to 3.5 g/tex) in an oxidizing atmosphere of 230 to 260°C
Implementation Method 3
carbonizing the resultant material at 300°C or higher in an inert-gas atmosphere
Data Source
AI summary
There is disclosed a method of producing a pre-oxidation fiber in the production of the pre-oxidation fiber by subjecting a polyacrylic precursor fiber to pre-oxidation processing in an oxidizing atmosphere, including shrinking the precursor fiber as a pretreatment of pre-oxidation at a load of 0.58 g/tex or less in the temperature range of 220 to 260°C under conditions in which the degree of cyclization (I1620/I2240) of the precursor fiber measured by a Fourier transform infrared spectrophotometer (FT-IR) does not exceed 7%, initially-drawing the precursor fiber at a load of 2.7 to 3.5 g/tex in an oxidizing atmosphere at 230 to 260°C in the ranges of the degree of cyclization of not exceeding 27% and of the density of not exceeding 1.2 g/cm3, and then subjecting the pre-oxidation fiber to pre-oxidation treatment. A carbon fiber of high strength and high elasticity that is appropriate for composite materials that exhibit high composite performance is obtained by continuously subjecting this pre-oxidation fiber to carbonization treatment.