Aliphatic Epoxy Resin Composition Viscosity Control
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Solution Overview
Problem
Conventional epoxy resin compositions for fiber-reinforced composite materials face challenges in achieving optimal impregnation, flexibility, and heat resistance, particularly in maintaining viscosity control during temperature changes, which affects their usability in complex-shaped aerospace and automotive applications.
Innovation Solution
An epoxy resin composition comprising an aliphatic epoxy resin with 1 hydroxyl group and 2 or more epoxy groups, another aliphatic epoxy resin with 0 hydroxyl groups and 3 epoxy groups, and a polyisocyanate compound, formulated to satisfy specific mass ratios, ensuring optimal viscosity and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the epoxy resin is thickened by reacting isocyanate with hydroxyl group, then the viscosity stability during storage and impregnating properties improve, but the flexibility and shapability deteriorate due to excessive viscosity
Solution Approach 1:
The patent changes the chemical parameters of the epoxy resin system by introducing a polyhydric alcohol component with multiple hydroxyl groups that can form multiple urethane bonds with isocyanate. By controlling the molecular weight and hydroxyl group density of the polyhydric alcohol, the patent achieves optimal viscosity thickening while maintaining flexibility. The specific parameter control involves selecting polyhydric alcohols with appropriate molecular weights and hydroxyl values to balance crosslinking density and chain flexibility.
Solution Approach 2:
The patent creates a composite resin system combining epoxy resin, polyisocyanate, and polyhydric alcohol in specific ratios. This composite approach allows the system to exhibit both the high viscosity stability from crosslinking and the flexibility from the polyhydric alcohol's molecular structure. The synergistic interaction between these components resolves the contradiction by distributing functions: epoxy provides base resin properties, isocyanate provides crosslinking for stability, and polyhydric alcohol provides flexibility through its molecular architecture.
2Ease of manufacture
If the epoxy resin composition has low viscosity for smooth impregnation, then the impregnating properties improve, but the heat resistance of the cured resin deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-forming a polyurethane-modified epoxy resin composition before the final curing process. The polyisocyanate and polyhydric alcohol are pre-reacted to form a modified epoxy resin with controlled viscosity and pre-established crosslinking structure. This preliminary modification ensures that the resin maintains low enough viscosity for impregnation while already containing the crosslinking architecture necessary for subsequent heat resistance development during curing.
Solution Approach 2:
The patent changes the chemical composition parameters by incorporating polyhydric alcohol with specific molecular weight ranges and hydroxyl group densities. This parameter control allows the resin to maintain appropriate viscosity for impregnation while the polyhydric alcohol's multiple hydroxyl groups ensure sufficient crosslinking density for heat resistance. The key parameter is the balance between molecular weight (affecting viscosity) and hydroxyl group density (affecting crosslinking and heat resistance).
3Ease of operation
If the molding material is made sufficiently flexible to follow mold shape, then the shapability improves, but the roll retention capability deteriorates
Solution Approach 1:
The patent controls the viscosity parameter within a specific range by adjusting the ratios of epoxy resin, polyisocyanate, and polyhydric alcohol. This controlled viscosity provides sufficient flexibility for the molding material to conform to complex mold shapes while maintaining enough structural integrity to retain roll shape during storage and handling. The key is optimizing the crosslinking density and molecular weight distribution to achieve the right balance between flexibility and shape retention.
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 composition provides excellent impregnation properties, controlled viscosity, and enhanced heat resistance, enabling flexible handling and flowability during press forming, resulting in high-performance fiber-reinforced composite materials with improved mechanical properties.
Implementation Method 1
reacting an epoxy group with an amine or an acid anhydride to form a crosslinked structure
Implementation Method 2
reacting an isocyanate with a hydroxyl group in an epoxy resin or a hydroxyl group in an alcohol to form a high-molecular-weight polyurethane in a system
Data Source
Figure 1
AI summary
The purpose of the present invention is to provide: an epoxy resin composition having excellent impregnating properties with respect to reinforcing fibers, and capable of providing an epoxy resin which has a post-thickening viscosity controlled to be in an optimal range, experiences little change in viscosity with respect to increased temperature, and has excellent post-curing heat resistance; a molding material for a fiber-reinforced composite material, the molding material having excellent handling flexibility and press-molding fluidity; and a fiber-reinforced composite material having excellent heat resistance and mechanical properties. The epoxy resin composition of the present invention for achieving the purpose contains components (A)-(C) below, and satisfies the expressions below: Component (A): an aliphatic epoxy resin having one hydroxyl group and two to three epoxy groups in one molecule; Component (B): an aliphatic epoxy resin having no hydroxyl group and three epoxy groups in one molecule; Component (C): a polyisocyanate compound; 0.125≤A/B≤3; and 0.2<(A+B)/T≤0.8(A: parts by mass of component (A), B: parts by mass of component (B), and T: total parts by mass of the epoxy resins in the epoxy resin composition).