Copolyamide-Sized Carbon Fiber Bundles for Resin Adhesion
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Solution Overview
Problem
Conventional sizing agents for carbon fiber bundles, such as epoxy-based and thermoplastic-resin-based agents, lead to hardened textures, reduced handleability, and insufficient properties in composite materials, especially when used with thermoplastic resins, and are prone to shedding during processing, resulting in inadequate reinforcing effects, particularly in applications like random mats.
Innovation Solution
A carbon fiber bundle with a sizing agent comprising a copolyamide resin containing specific repeating units, which adheres to the fibers with a melting point of 180°C or lower, providing excellent adhesion and handleability while minimizing shedding, and is suitable for use in composite materials with both thermosetting and thermoplastic resins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional epoxy-based or thermoplastic-resin-based sizing agents are used, then interfacial bonding strength is improved, but the texture of carbon fiber bundles becomes hardened and handleability is reduced
Solution Approach 1:
The invention changes the chemical composition parameters of the sizing agent by using a copolymer of polyolefin and polyamide instead of conventional epoxy or thermoplastic resins. This compositional parameter change maintains interfacial bonding strength while improving handleability and preventing texture hardening of the carbon fiber bundles.
2Strength
If epoxy-based sizing agent is used, then satisfactory performance is achieved with thermosetting resins, but high bonding strength cannot be obtained with thermoplastic resins due to poor compatibility
Solution Approach 1:
The copolymer sizing agent comprising polyolefin and polyamide components provides universal compatibility with both thermosetting and thermoplastic resins. The polyolefin component ensures compatibility with thermoplastic resins while the polyamide component provides bonding capability with thermosetting resins, making the sizing agent versatile for different resin systems.
3Strength
If water-soluble polyamide resin is used as sizing agent, then adhesion is improved, but the sized carbon fiber bundles have high hygroscopicity and are unusable in applications requiring long processing steps
Solution Approach 1:
The invention creates a composite sizing agent system by combining polyolefin and polyamide in a copolymer structure. This composite material approach leverages the hydrophobic nature of polyolefin to reduce hygroscopicity while maintaining the adhesion benefits of polyamide, thereby solving the moisture absorption problem of water-soluble polyamide resins.
4Ease of operation
If conventional sizing agents are used, then bundling properties are enhanced, but the carbon fibers have too high bundling properties causing insufficient dispersion in composite materials
Solution Approach 1:
The copolymer sizing agent provides localized quality control by having different segments (polyolefin and polyamide) that perform different functions. The polyolefin segment provides appropriate bundling for handleability while the polyamide segment ensures proper dispersion and adhesion, creating a balanced local quality distribution on the fiber surface.
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 carbon fiber bundle exhibits improved adhesion to matrix resins, reduced shedding of the sizing agent during processing, and enhanced reinforcing effects, leading to higher quality composite materials with improved mechanical properties and processability.
Implementation Method 1
a sizing agent which comprises a copolyamide resin... the sizing agent adheres in an amount of 0.01 to 10 parts by weight in terms of final dry-basis weight of the sizing agent per 100 parts by weight of the carbon fiber bundle
Implementation Method 2
the copolyamide resin having a melting point of 180°C or lower
Data Source
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AI summary
The present invention relates to a carbon fiber bundle excellent in terms of adhesion to matrix resins and process handleability and less apt to suffer the shedding of the sizing agent in processing steps. The carbon fiber bundle of the invention is a carbon fiber bundle having a sizing agent adherent to the surface thereof, characterized in that the carbon fiber bundle includes a plurality of carbon fibers and the sizing agent includes a copolyamide resin, the copolyamide resin having both a specific polyamide component and nylon-6 and/or nylon-66 as repeating units and having a melting point of 180°C or lower. The melting point of the copolymer resin is preferably 60 to 160°C, and the glass transition temperature thereof is preferably in the range of -20 to 50°C.