Blocked Isocyanate Sizing Agent Composition for Carbon Fiber Adhesion
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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 with an aliphatic skeleton and a compound containing polar and unsaturated groups, specifically an ester compound of polyalkylene glycol and unsaturated carboxylic acid, is used to enhance adhesion by forming a covalent bond with the fiber surface, improving storage stability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface oxidation treatment is applied to carbon fiber to improve adhesion, then adhesion between carbon fiber and matrix resin is improved, but the treatment is ineffective for high-modulus carbon fibers where activation reaction is unlikely to occur
Solution Approach 1:
The invention changes the chemical parameters of the sizing agent by using a compound containing both isocyanate groups and carboxyl groups in specific proportions. This dual-functional compound can react with both the carbon fiber surface and the matrix resin, creating effective adhesion without relying on surface oxidation treatment that fails for high-modulus fibers.
Solution Approach 2:
The sizing agent itself acts as a composite chemical structure combining two different functional groups (isocyanate and carboxyl) in one molecule. This allows it to perform multiple functions: bonding to carbon fiber through one group and bonding to matrix resin through the other group, thereby resolving the adaptability issue across different fiber types.
2Object-generated harmful factors
If conventional sizing agents are used to suppress fuzzing, then bundling property is improved, but adhesion between carbon fiber and matrix resin remains unsatisfactory
Solution Approach 1:
The sizing agent compound performs multiple functions simultaneously: it provides bundling property to suppress fuzzing while also creating strong adhesion between carbon fiber and matrix resin. This is achieved by the compound's dual functionality - containing both isocyanate groups for fiber bonding and carboxyl groups for resin interaction, plus appropriate molecular weight for bundling.
3Strength
If a sizing agent with terminal unsaturated group and polar group is used (PTL 1), then some adhesion improvement is achieved, but satisfactory adhesion cannot be obtained
Solution Approach 1:
The invention optimizes the chemical composition parameters by specifying exact functional group types (isocyanate and carboxyl) and their proportion range (0.1-10 mmol/g carboxyl content, with isocyanate to carboxyl molar ratio of 0.1-10). This precise parameter control enables reliable and satisfactory adhesion performance that PTL 1 failed to achieve.
4Strength
If a sizing agent with epoxy group and vinyl group per molecule is used (PTL 2), then some adhesion improvement is achieved, but satisfactory adhesion cannot be obtained
Solution Approach 1:
The invention replaces the epoxy-vinyl group combination with an isocyanate-carboxyl group combination. The isocyanate groups provide stronger and more reliable bonding to carbon fiber surfaces, while the carboxyl groups effectively interact with the matrix resin system, achieving satisfactory adhesion performance that PTL 2's epoxy-vinyl approach failed to deliver.
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 addressing the limitations of existing technologies.
Implementation Method 1
enhance adhesion by forming a covalent bond with the fiber surface
Implementation Method 2
imparting a bundling property to the carbon fiber by the sizing treatment, it is possible to suppress fuzzing
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.