Chopped Carbon Fiber Bundle Sizing for High-Fluidity Compounding
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Solution Overview
Problem
The production of chopped carbon fiber bundles with high fluidity and productivity is challenging when using carbon fiber bundles with a large number of filaments and high total fineness, as they tend to have low flatness, leading to issues with sizing agent penetration, cohesion, and increased shear forces, resulting in fibrillation and clogging during the compounding process.
Innovation Solution
A chopped carbon fiber bundle with a total fineness of 25,000 to 45,000 dtex and a sizing agent content of 1% to 5% by mass, characterized by a length of 1 mm to 50 mm, a diameter ratio of 6.0 to 18.0, and an orientation parameter of 4.0 or less, using thermoplastic resin-based sizing agents, and a method involving primary and secondary sizing agent application followed by cutting and drying to achieve uniform cohesion and handleability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon fiber bundles with a large number of filaments and high total fineness are used to reduce production cost, then cost reduction is achieved, but the bundles have low flatness which causes poor sizing agent penetration and low fluidity
Solution Approach 1:
The patent applies parameter changes by controlling the width of carbon fiber bundles within a specific range (1/220 mm/tex to 1/80 mm/tex) and adjusting the sizing agent viscosity (3000 Pa·s or less). These parameter optimizations enable large fineness bundles (25,000-45,000 dtex) to maintain both cost-effectiveness and adequate fluidity for processing
Solution Approach 2:
The patent applies local quality by using a two-stage sizing agent application system. A primary sizing agent with low viscosity is applied first to ensure penetration into the bundle interior, followed by a secondary sizing agent to provide surface cohesion. This localized differentiation of sizing agent properties solves the penetration-cohesion contradiction
2Ease of manufacture
If the flatness of carbon fiber bundles is increased to improve sizing agent penetration, then penetration is improved, but the bundles exhibit low fluidity and low bundling properties
Solution Approach 1:
The patent optimizes the width parameter of carbon fiber bundles to a specific range (1/220 mm/tex to 1/80 mm/tex) that balances penetration capability with fluidity. This parameter control ensures bundles are flat enough for sizing agent access but not so flat that they lose bundling properties and fluidity
Solution Approach 2:
The patent uses a composite sizing agent system combining primary and secondary sizing agents with different functional properties. The primary agent (low viscosity, 3000 Pa·s or less) provides penetration, while the secondary agent provides cohesion, creating a composite functional system that resolves the penetration-fluidity contradiction
3Volume of stationary object
If the cross-sectional shape approaches circular to increase bulk density, then bulk density is increased, but sizing liquid penetration becomes difficult and cohesion becomes irregular
Solution Approach 1:
The patent changes the cross-sectional shape parameter from circular to flattened, with width controlled in the range of 1/220 mm/tex to 1/80 mm/tex. This shape modification increases the surface area available for sizing liquid penetration while maintaining adequate bulk density for handling and processing
4Productivity
If shear force in compounding process is increased, then mixing is improved, but carbon fiber bundles are easily fibrillated and fiber balls are generated
Solution Approach 1:
The patent optimizes the viscosity parameter of the primary sizing agent to 3000 Pa·s or less. This viscosity control creates adequate lubrication between fibers during compounding, reducing shear forces to levels that prevent fibrillation and fiber ball formation while still allowing effective mixing and dispersion
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 solution enhances the processability and handleability of the chopped carbon fiber bundles, resulting in improved mechanical characteristics and increased productivity by ensuring uniform sizing agent distribution and fiber orientation, reducing fibrillation and clogging issues.
Implementation Method 1
the sizing agent can easily penetrate into the interior of the carbon fiber bundle
Implementation Method 2
a method involving primary and secondary sizing agent application
Data Source
AI summary
Provided are: chopped carbon fiber bundles which have high fluidity without decreasing the dispersibility of carbon fibers and the physical properties of a molded product; and a method for producing chopped carbon fiber bundles with high productivity. Chopped carbon fiber bundles, each of which contain a carbon fiber bundle having a total fineness of from 25,000 dtex to 45,000 dtex (inclusive) and a sizing agent in an amount of from 1% by mass to 5% by mass (inclusive) relative to the total mass of the chopped carbon fiber bundle. The length (L) of each chopped carbon fiber bundle along the fiber direction of the carbon fiber bundle is from 1 mm to 50 mm (inclusive); the ratio of the longest diameter (Dmax) to the shortest diameter (Dmin) of a cross section perpendicular to the fiber direction of each chopped carbon fiber bundle, namely Dmax/Dmin is from 6.0 to 18.0 (inclusive); and the orientation parameter of the single fibers present in the surface of each chopped carbon fiber bundle is 4.0 or less.