Epoxy Resin Blend Reduces SO2 Emissions and Self-Extinguishing Time
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Solution Overview
Problem
High performance epoxy resins used in aerospace applications emit toxic sulfur-containing gases when burned, posing a concern for flammability and self-extinguishing times, while maintaining structural strength and uncured resin properties is crucial.
Innovation Solution
A blend of epoxy resins with polyetherimide and polyamideimide thermoplastic toughening agents, along with a curative agent, is used to reduce sulfur emissions and achieve short self-extinguishing times without compromising structural strength or uncured resin properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sulfur-containing thermoplastic tougheners (such as polyether sulfone) are used to toughen high performance epoxy resins, then the structural strength and toughness of the cured composite part are improved, but the SO2 emission level increases to over 100 ppm when the resin is burned
Solution Approach 1:
The patent changes the chemical composition parameters of the thermoplastic toughener by replacing sulfur-containing polyether sulfone with sulfur-free alternatives such as polyetherimide and polyamideimide. This parameter change maintains the toughness function while eliminating the harmful SO2 emissions, achieving compliance with the 100 ppm emission limit
Solution Approach 2:
The patent uses a blend of multiple thermoplastic tougheners (polyetherimide and polyamideimide) to create a composite toughening system. This composite approach provides synergistic effects that maintain or enhance structural strength and toughness while avoiding the use of sulfur-containing compounds that would generate excessive SO2 emissions
2Strength
If sulfur-containing curing agents are used to cure high performance epoxy resins, then the structural strength of the cured composite part is maintained, but the self-extinguishing time increases and burn properties deteriorate
Solution Approach 1:
The patent changes the chemical composition of the curing agent system by using sulfur-free or low-sulfur curing agents. This parameter change improves the burn properties and reduces self-extinguishing time while maintaining the required structural strength through optimized curing chemistry and formulation
3Strength
If thermoplastic tougheners are added to high performance epoxy resins to improve toughness, then the structural strength is enhanced, but the tack and viscosity of the uncured resin are adversely affected
Solution Approach 1:
The patent optimizes the molecular weight, glass transition temperature, and chemical structure parameters of the thermoplastic tougheners (polyetherimide and polyamideimide). By carefully selecting these parameters, the patent achieves effective toughness enhancement while minimizing the negative impact on uncured resin properties such as tack and viscosity, ensuring proper prepreg fabrication
Data Source
AI summary
Epoxy resin compositions that generate reduced levels of sulfur dioxide and which unexpectedly have reduced self-extinguishing times. The epoxy resins are composed of from 50 to 70 weight percent of an epoxy resin component. The epoxy resin composition also includes from 15 to 35 weight percent of a thermoplastic blend that is composed of polyetherimide and polyamideimide. The epoxy resin composition further includes from 5 to 25 weight percent of a curative agent.