Method for producing carbon fiber and carbon fiber produced using same
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Solution Overview
Problem
Carbon fibers without a sizing agent suffer from cohesion issues and unwinding defects, leading to fiber breakage and poor mechanical properties in composite materials, especially when used with thermoplastic resins.
Innovation Solution
A method involving the production of carbon fibers using a polyacrylonitrile-based precursor with a narrow molecular weight distribution, followed by a thermally stabilizing and carbonization process, and the application of a smoothing agent like alkyl ether or aliphatic ester compounds before winding, eliminating the need for a resin-based sizing agent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a sizing agent including a thermosetting resin component is applied to carbon fiber, then fiber cohesion and winding stability are improved, but voids or pores occur in thermoplastic composite materials due to thermal decomposition of the sizing agent
Solution Approach 1:
The invention extracts and removes the thermosetting resin component from the sizing agent formulation, retaining only the water-soluble polymer component that provides cohesion without causing thermal decomposition issues in thermoplastic composite materials
Solution Approach 2:
The invention changes the chemical composition parameters of the sizing agent by specifying water-soluble polymers with particular molecular weight ranges (10,000-1,000,000 g/mol) and excluding thermosetting resin components, thereby achieving compatibility with thermoplastic matrices
2Object-affected harmful factors
If no sizing agent is applied to carbon fiber bundle, then fiber cohesion issues are avoided for thermoplastic applications, but carbon fiber bundle has no cohesion and is difficult to wind
Solution Approach 1:
The invention introduces a water-soluble polymer as an intermediary substance that provides temporary cohesion during handling and winding operations, which can be easily removed or does not interfere with subsequent thermoplastic processing
Solution Approach 2:
The sizing agent using water-soluble polymers serves as a temporary, easily removable coating that fulfills its cohesion function during processing but does not persist to interfere with final composite material performance
3Object-affected harmful factors
If carbon fiber is wound without a sizing agent, then thermal decomposition issues are avoided, but fibers are entangled together and fiber breakage occurs during unwinding
Solution Approach 1:
The invention extracts the problematic thermosetting resin component from traditional sizing agents while retaining the functional benefits of cohesion and unwinding stability through water-soluble polymers alone
Solution Approach 2:
The invention optimizes the molecular weight parameters of water-soluble polymers (10,000-1,000,000 g/mol) to achieve appropriate viscosity and cohesion properties that prevent fiber entanglement and breakage during unwinding
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
This approach stabilizes carbon fiber bundles for easy winding and unwinding, maintains high-quality fiber properties, and enhances their suitability for high-temperature processing with thermoplastic resins, reducing defects and fiber breakage.
Implementation Method 1
an acrylic fiber obtained by spinning the PAN polymer, i.e., a carbon fiber precursor, is subjected to thermally stabilizing treatment at 200 to 400° C. under an oxidation atmosphere
Implementation Method 2
The stabilized fiber thus obtained is carbonized at 800 to 2,000° C. under an inert gas atmosphere to produce carbon fiber
Data Source
AI summary
The present invention is a method for producing carbon fiber, characterized by using a carbon-fiber precursor produced from a polymer having a narrow molecular weight distribution and by applying only a small amount of a smoothing agent, composed of a specific component, to the carbon fiber surface immediately before winding of carbon fiber. According to the present invention, it is possible to stably produce carbon fiber, which has excellent dispersibility and do not deteriorate in quality and quality even when a sizing agent is not attached to the carbon fiber surface. In addition, the produced carbon fiber is suitable for use in a composite material which is produced by high-temperature processing using a thermoplastic resin.