Sizing agent composition, method for producing carbon fibers, and carbon fibers each having sizing agent applied thereonto
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Solution Overview
Problem
Conventional sizing agents fail to achieve satisfactory adhesion between carbon fibers and matrix resins, particularly in high-modulus carbon fibers, leading to suboptimal mechanical properties in composite materials.
Innovation Solution
A sizing agent composition comprising a blocked isocyanate and a compound with both polar and unsaturated groups per molecule, applied in a specific ratio, which reacts with the fiber surface to form a crosslinked structure, enhancing adhesion to radically polymerizable resins like unsaturated polyester or vinyl ester.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional sizing agents are used to suppress fuzzing, then fiber bundling property is improved, but adhesion between carbon fiber and matrix resin deteriorates
Solution Approach 1:
The invention changes the chemical parameters of the sizing agent by incorporating specific functional groups (isocyanate groups, carboxyl groups, hydroxyl groups, or amino groups) in controlled amounts. This allows the sizing agent to provide both bundling properties and adhesion promotion simultaneously through chemical reactions with the matrix resin, resolving the contradiction between ease of operation and strength.
Solution Approach 2:
The invention creates a composite sizing agent system combining multiple functional components: compounds with specific functional groups (isocyanate, carboxyl, hydroxyl, or amino groups) and compounds with terminal unsaturated groups. This composite approach enables the sizing agent to perform multiple functions - both fiber bundling and adhesion enhancement - thereby resolving the contradiction between operational ease and bonding strength.
2Strength
If surface oxidation treatment is applied to activate carbon fiber surface, then adhesion is improved, but activation reaction is insufficient in high-modulus carbon fibers
Solution Approach 1:
The invention introduces a sizing agent as an intermediary substance that contains reactive functional groups (isocyanate, carboxyl, hydroxyl, or amino groups). This intermediary mediates the bonding between the carbon fiber surface and the matrix resin, enabling effective adhesion even when surface oxidation treatment is insufficient, particularly in high-modulus carbon fibers.
Solution Approach 2:
The invention changes the chemical parameters by incorporating specific functional groups in controlled amounts (isocyanate groups, carboxyl groups, hydroxyl groups, or amino groups) within the sizing agent. These functional groups can react with the matrix resin to form strong chemical bonds, compensating for insufficient surface activation in high-modulus carbon fibers.
3Strength
If compound with terminal unsaturated group and polar group is used as sizing agent, then adhesion effect is attempted, but satisfactory adhesion cannot be achieved
Solution Approach 1:
The invention enhances the chemical parameters by incorporating specific functional groups (isocyanate groups, carboxyl groups, hydroxyl groups, or amino groups) in controlled amounts within the sizing agent. These functional groups provide stronger and more reliable reaction pathways with the matrix resin compared to conventional terminal unsaturated groups alone, achieving satisfactory adhesion performance.
Solution Approach 2:
The invention creates a composite sizing agent system that combines compounds with specific functional groups (isocyanate, carboxyl, hydroxyl, or amino groups) and compounds with terminal unsaturated groups. This composite structure enables both the desired adhesion effect and satisfactory manufacturing precision by providing multiple reaction mechanisms for strong bonding.
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 proposed sizing agent composition significantly improves the adhesion between carbon fibers and matrix resins, resulting in composite materials with enhanced mechanical properties and reduced fuzzing, thereby improving the handling and reinforcing capabilities of carbon fiber bundles.
Implementation Method 1
reacts with the fiber surface to form a crosslinked structure, enhancing adhesion to radically polymerizable resins
Implementation Method 2
adhesion to radically polymerizable resins like unsaturated polyester or vinyl ester
Data Source
AI summary
An object of the present invention is to provide a sizing agent composition that gives a carbon fiber from which a carbon fiber-reinforced composite material having excellent adhesion between a resin and the carbon fiber and having excellent mechanical properties can be formed. The sizing agent composition of the invention is a sizing agent composition comprising (A) a blocked isocyanate, and (B) a compound containing at least one polar group and at least one unsaturated group per molecule. In the invention, the mixing ratio (mass ratio) of the blocked isocyanate (A) and the compound (B) containing at least one polar group and at least one unsaturated group per molecule (A/B) is preferably 95/5 to 5/95. In the invention, the blocked isocyanate (A) is preferably a compound having an aliphatic skeleton.