Carbon Fiber Bundle Twist Control for Thermal Stability
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Solution Overview
Problem
Existing carbon fiber bundles lack sufficient bundle forming property at high temperatures, leading to thermal degradation and high production costs, and current techniques fail to address issues such as fuzz generation, thermal degradation products, and the need for sizing agents.
Innovation Solution
A carbon fiber bundle with a twist count of 2 turns/m or more, single fiber diameter of 6.1 µm or more, and a heat loss rate of 0.15% or less, meeting the formula π 002 > 4.0 × L c + 73.2, along with a surface layer twist angle of 0.2° or more, enhances handleability and processability while reducing thermal degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a sizing agent is used to impart bundle forming property to carbon fiber bundles, then handleability and high-order processability are improved, but thermal degradation products increase during high-temperature molding processes
Solution Approach 1:
The invention extracts and removes the sizing agent from the carbon fiber bundle system. By creating carbon fiber bundles with inherent bundle forming property through controlled twisting during manufacturing, the patent eliminates the need for sizing agents, thereby preventing thermal degradation products while maintaining handleability and processability.
Solution Approach 2:
The carbon fiber bundles are designed to possess self-service capabilities through inherent bundle forming property. The controlled twisting structure enables the bundles to maintain their form and stability without external sizing agents, allowing them to serve their own handling and processing needs inherently.
2Ease of operation
If a sizing agent is applied to carbon fiber bundles to enhance bundle forming property, then high-order processability improves, but production cost increases
Solution Approach 1:
The invention extracts the sizing agent dependency from the manufacturing process. By incorporating bundle forming property directly into the carbon fiber bundle structure through controlled twisting during production, the patent eliminates the need for additional sizing agent materials and application steps, thereby reducing production costs while maintaining high-order processability.
3Reliability
If carbon fiber bundles are used without sufficient bundle forming property, then thermal degradation occurs during high-temperature molding, but adding sizing agents to prevent degradation increases thermal degradation products
Solution Approach 1:
The invention converts the potential harm of insufficient bundle forming property into a benefit by designing a controlled twisting structure that provides inherent thermal stability. The specific twist configurations (2-10 turns/m for straight bundles, 3-15 degrees for angled bundles) create structural integrity that resists thermal degradation without requiring sizing agents, thus preventing thermal degradation products.
Data Source
AI summary
An object is to obtain a carbon fiber that achieves both a strong bundle forming property and a thermal stability in a good balance and serves to realize a reduction in the molding cost and improvement in performance when producing a carbon fiber reinforced composite material containing a highly heat resistant resin as matrix. The carbon fiber bundle according to the present invention is one that satisfies the following requirements: retaining a twist count of 2 turns/m or more when suspended with one end fixed and the other end free; having a required single fiber diameter and a required heat loss rate, and meeting a specified formula expressing a relationship between the crystallite size Lc and the orientation parameter of crystallites π002 determined from bulk measurement of the entire fiber bundle. Also provided is a method for producing a carbon fiber bundle having a required single fiber diameter and a required heat loss rate, including steps for performing stabilization of a precursor fiber bundle for polyacrylonitrile based carbon fiber, pre-carbonization thereof, and carbonization thereof performed in this order, the twist count and tension of the fiber bundle being 2 turns/m or more and 1.5 mN/dtex or more, respectively, in the carbonization step. In addition, also provided is a carbon fiber bundle that satisfies the following requirements: retaining a fiber bundle surface layer twist angle of 0.2° or more when suspended with one end fixed and the other end free; having a required single fiber diameter and a required heat loss rate; and meeting a specified formula expressing a relationship between the crystallite size Lc and the orientation parameter of crystallites π002 determined from bulk measurement of the entire fiber bundle. Also provided is a method for producing a carbon fiber bundle retaining a fiber bundle surface layer twist angle of 0.2° or more when suspended with one end fixed and the other end free and having a required single fiber diameter and a required heat loss rate, including steps for performing stabilization of a precursor fiber bundle for polyacrylonitrile based carbon fiber, pre-carbonization thereof, and carbonization thereof performed in this order, the tension being 1.5 mN/dtex or more in the carbonization step.