Vinyl Ester Fiber Sizing Agent for Carbon Fiber Interlaminar Strength
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Solution Overview
Problem
Existing fiber sizing agents, particularly those used for carbon fibers, fail to provide sufficient sizing properties and strength to molded articles, resulting in inadequate mechanical properties such as bending strength, compressive strength, and interlaminar shear strength.
Innovation Solution
A fiber sizing agent comprising a vinyl ester resin with an alkoxy polyoxyalkylene structure and a urethane bond, combined with an aqueous medium, is used to enhance the sizing properties and strength of glass and carbon fibers, leading to improved physical properties in molded articles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional fiber sizing agents (aliphatic epoxy compound + compound with terminal unsaturated group and polar group) are used, then fiber bundling is achieved, but sizing properties of carbon fibers are insufficient and strength of molded articles is insufficient
Solution Approach 1:
The invention uses a composite resin system comprising both an aliphatic epoxy compound and a vinyl ester resin with specific functional groups. This composite approach combines the adhesive properties of epoxy with the flexibility and sizing properties of vinyl ester, achieving both strong fiber-matrix bonding and excellent carbon fiber sizing properties that neither component could achieve alone.
Solution Approach 2:
The invention specifies precise parameter ranges for the vinyl ester resin including (meth)acryloyl equivalent (500-3000 g/equivalent), hydroxyl value (10-100 mg KOH/g), and number average molecular weight (1000-5000). These parameter optimizations ensure the resin provides adequate viscosity for fiber coating while maintaining reactivity and bonding strength, resolving the contradiction between sizing properties and molded article strength.
2Productivity
If fiber materials are bundled to several thousands to several tens of thousands by fiber sizing agent, then high strength is imparted, but the sizing properties and strength are insufficient when conventional agents are used
Solution Approach 1:
The composite resin system combines aliphatic epoxy compound (providing strong adhesion for fiber bundling) with vinyl ester resin (providing flexibility and enhanced mechanical properties). This synergy enables effective fiber bundling while simultaneously achieving high bending and compressive strength in the final molded article.
Solution Approach 2:
The vinyl ester resin with hydroxyl groups provides local chemical bonding sites at the fiber-matrix interface, creating strong interfacial adhesion. This localized bonding enhancement at critical interfaces (fiber surfaces) translates to improved overall mechanical strength while maintaining the fiber bundling capability.
3Ease of operation
If existing fiber sizing agents are used for carbon fibers, then fiber processing is enabled, but interlaminar shear strength and other mechanical properties are inadequate
Solution Approach 1:
The invention optimizes the hydroxyl value of the vinyl ester resin to 10-100 mg KOH/g, providing adequate hydroxyl groups for hydrogen bonding with carbon fiber surfaces. This parameter optimization enhances interlaminar shear strength while maintaining processing ease. The (meth)acryloyl equivalent of 500-3000 g/equivalent ensures proper viscosity and reactivity for fiber impregnation.
Solution Approach 2:
The vinyl ester resin acts as an intermediary between the carbon fibers and the matrix resin system. Its specific chemical structure with hydroxyl groups and (meth)acryloyl groups enables it to bond effectively with both carbon fiber surfaces and the surrounding matrix, improving interlaminar shear strength while facilitating smooth fiber processing.
Data Source
AI summary
A fiber sizing agent includes: a vinyl ester resin (A) having an alkoxy polyoxyalkylene structure and a urethane bond; and an aqueous medium. The fiber sizing agent has excellent fiber sizing properties for various fibers such as glass fibers and carbon fibers. A molded article obtained from a molding material including the fiber sizing agent is excellent in various physical properties such as bending strength, compressive strength, and interlaminar shear strength, and thus can be used, for example, for an automobile member, an aircraft member, a windmill member, and an industrial member.