Sizing agent coated carbon fiber, method for producing sizing agent coated carbon fiber, carbon fiber reinforced composite material, and method for producing carbon fiber reinforced composite material
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Solution Overview
Problem
Existing methods for improving adhesion and processability of carbon fibers in composite materials do not effectively address the need for high electrical insulation properties, despite surface treatments and sizing agents being used.
Innovation Solution
A sizing agent coated carbon fiber with a specific surface structure, where the carbon fiber has an oxygen layer of 4% or more in a 10 nm thickness and is coated with a sizing agent comprising polyimide, polyetherimide, and polysulfone, along with a polyether-type aliphatic epoxy compound, to enhance electrical insulation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon fiber is subjected to oxidation treatment to improve adhesion, then adhesion strength is improved, but electrical insulation properties deteriorate
Solution Approach 1:
The patent applies preliminary oxidation treatment to the carbon fiber surface before sizing agent coating to create oxygen-containing functional groups. This preliminary action improves adhesion strength while the subsequent sizing agent coating restores electrical insulation properties, resolving the contradiction between adhesion improvement and electrical insulation maintenance
Solution Approach 2:
The sizing agent acts as an intermediary substance between the oxidized carbon fiber surface and the matrix resin. It contains epoxy groups that react with carboxyl groups on the carbon fiber surface to form strong chemical bonds, while also providing electrical insulation properties to maintain the electrical characteristics of the composite material
2Ease of operation
If sizing agent is coated on carbon fiber to improve processability, then high-order processing properties are improved, but electrical insulation properties deteriorate
Solution Approach 1:
The patent carefully controls the oxygen concentration on the carbon fiber surface (0.03-0.08 mass ratio) and the epoxy equivalent of the sizing agent (200-400 g/eq) to optimize both processing properties and electrical insulation. By adjusting these parameters, the sizing agent provides sufficient adhesion and processability while maintaining the electrical characteristics of the carbon fiber reinforced composite material
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 achieves high electrical insulation properties in carbon fiber reinforced composite materials by ensuring a specific surface structure and composition of the sizing agent, leading to improved interaction and localization of the sizing agent on the carbon fiber surface.
Implementation Method 1
a carbon fiber surface treatment and a sizing agent are used for the purpose of improving the adhesion and high-order processability
Implementation Method 2
a method in which the carbon fiber is subjected to an oxidation treatment such as gas-phase oxidation or liquid-phase oxidation, thereby introducing oxygen-containing functional groups into the carbon fiber surface
Data Source
AI summary
Sizing agent coated carbon fibers obtained by coating carbon fibers with a sizing agent comprising at least one of (A) to (C) in a total amount of 80 mass % or more with respect to the whole sizing agent, the carbon fibers each having a surface layer which has a thickness of 10 nm or larger and has an oxygen content of 4% or higher with respect to all the elements, wherein when the sizing agent coated carbon fibers are subjected three times to a 10-minute ultrasonic treatment in an acetone solvent, then the amount of the remaining sizing agent is 0.1-0.25 parts by mass per 100 parts by mass of the sizing agent coated carbon fibers. (A) At least one polymer selected from the group consisting of polyimides, polyetherimides, and polysulfones (B) A compound having a terminal unsaturated group and a polar group in the molecule (C) A polyether-type aliphatic epoxy compound and/or a polyol-type aliphatic epoxy compound which each have an epoxy equivalent of 250 g/eq or less and have two or more epoxy groups in the molecule.