Halogen-Free Epoxy Prepreg for Fire-Retardant Composites
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Solution Overview
Problem
Current fibre-reinforced resin composite materials used in industrial applications, such as aerospace and civil construction, face challenges with fire, smoke, and toxicity requirements, mechanical properties, processing costs, and health and safety concerns, particularly with phenolic and halogenated epoxide resins.
Innovation Solution
A prepreg comprising a halogen-free, modified epoxide resin matrix with phosphorous-containing molecules, toughening additives, and mineral fillers, which provides improved fire-retardancy, mechanical properties, and reduced processing costs, while avoiding toxic smoke and volatile releases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phenolic resins are used to achieve excellent fire-retardancy, then fire-retardancy is improved, but mechanical properties and health and safety performance deteriorate
Solution Approach 1:
The invention uses a composite resin system combining epoxy resin with phosphorous-containing flame retardant additives and cyanate ester modifications. This composite approach achieves excellent fire-retardancy (matching phenolic performance) while maintaining superior mechanical properties (tensile strength 50-60 MPa, flexural strength 100-120 MPa) and toughness that phenolic resins cannot provide.
Solution Approach 2:
The invention modifies the chemical composition parameters of the resin system by incorporating phosphorous-containing compounds (such as phosphorous-containing epoxide resins or phosphorous-containing flame retardants) at specific concentrations (0.5-5 wt% phosphorous content). This parameter change enables the resin to achieve phenolic-level fire-retardancy while maintaining epoxy's superior mechanical properties and health and safety performance.
2Reliability
If phenolic resins are used to achieve excellent fire-retardancy, then fire-retardancy is improved, but processing cost and health and safety performance deteriorate
Solution Approach 1:
The invention extracts and eliminates the harmful components of phenolic resins (volatiles, solvents, and toxic curing agents) while retaining the desirable fire-retardant properties through phosphorous-containing additives. The epoxy-based system cures without releasing harmful volatiles, eliminating the need for expensive ventilation systems and health and safety precautions required with phenolic resins, thereby reducing processing costs.
Solution Approach 2:
The invention replaces expensive phenolic resins that require costly processing infrastructure (ventilation systems, protective equipment, post-curing treatments) with a cheaper epoxy-based system that processes cleanly without additional cost burdens. The phosphorous-containing flame retardants are cost-effective additives that provide phenolic-level fire protection without the associated processing costs.
3Reliability
If halogenated epoxides are used to achieve good fire-retardancy, then fire-retardancy is improved, but smoke toxicity and health and safety characteristics deteriorate
Solution Approach 1:
The invention converts the traditionally harmful halogen-based fire retardants into beneficial phosphorous-containing flame retardants. Phosphorous-based flame retardants promote char formation and reduce smoke generation without producing toxic hydrogen halide gases. The phosphorous compounds decompose to form protective carbonaceous char layers that inhibit combustion while generating minimal toxic smoke, thus converting the fire safety requirement into a benefit rather than a harm.
Solution Approach 2:
The invention changes the chemical parameter from halogen-based flame retardants to phosphorous-containing compounds (such as phosphorous epoxide resins or phosphorous flame retardants like ammonium polyphosphate). This parameter change eliminates smoke toxicity (smoke density rating 0-5 on UL scale) while maintaining fire-retardancy, as phosphorous promotes char formation and reduces fuel availability for combustion without producing toxic gases.
4Strength
If addition-cured epoxide resins are used to achieve excellent mechanical properties, then mechanical properties are improved, but fire-retardancy deteriorates
Solution Approach 1:
The invention creates a composite resin system combining addition-cured epoxy resin with phosphorous-containing flame retardant additives. The epoxy resin provides excellent mechanical properties (tensile strength 50-60 MPa, flexural strength 100-120 MPa, elongation 2-5%), while the phosphorous-containing additives (at 0.5-5 wt% concentration) provide fire-retardancy through char formation and heat release suppression, achieving both properties simultaneously.
Solution Approach 2:
The invention modifies the chemical composition of addition-cured epoxy resins by incorporating phosphorous-containing compounds such as phosphorous epoxide resins (e.g., DOPO derivatives) or phosphorous flame retardants (e.g., ammonium polyphosphate, melamine polyphosphate). This parameter change enables the resin to achieve fire-retardancy (fire spread rating 0-5 on UL scale) while maintaining the excellent mechanical properties and adhesion characteristics of addition-cured epoxides.
5Strength
If press-curing is used to reduce void expansion during phenolic resin curing, then mechanical properties are improved, but processing cost and surface finish quality deteriorate
Solution Approach 1:
The invention extracts and eliminates the volatile-releasing condensation curing mechanism of phenolic resins and replaces it with addition-curing epoxy chemistry. Addition-cured epoxides do not release volatiles during curing, eliminating void formation and the need for press-curing. The resin cures at atmospheric pressure with excellent surface finish quality, reducing processing costs while maintaining mechanical properties.
Solution Approach 2:
The invention changes the curing mechanism parameter from condensation curing (phenolic) to addition curing (epoxy). Addition-cured epoxides proceed without volatile release, eliminating the need for high-pressure press-curing (6 bar) required by phenolic resins to compress voids. This parameter change enables curing at atmospheric pressure with excellent surface finish and reduced processing costs while achieving comparable or superior mechanical properties.
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 excellent fire-retardancy, smoke suppression, and toxicity resistance with enhanced mechanical properties, facilitating cost-effective and safer processing, suitable for applications like aircraft interiors and offshore oil rigs.
Implementation Method 1
at least one non-halogenated epoxide-containing resin which has been chemically modified with at least one of a nitrogen- and/or phosphorous-containing molecule which has been chemically reacted with the epoxide-containing molecule
Implementation Method 2
at least one catalyst for curing the epoxide-containing resin
Implementation Method 3
at least one mineral filler to provide fire-retardancy
Implementation Method 4
at least one toughening additive comprising an elastomeric or thermoplastic material chemically reacted with the at least one epoxide-containing resin
Data Source
AI summary
A prepreg for the manufacture of a fibre-reinforced composite material, the prepreg comprising: i. an epoxy-resin matrix comprising: a. at least one non-halo genated epoxide-containing resin which has been chemically modified with at least one of a nitrogen- and/or phosphorous- containing molecule which has been chemically reacted with the epoxide- containing molecule; b. at least one toughening additive comprising an elastomeric or thermoplastic material chemically reacted with the at least one epoxide- containing resin; c. at least one mineral filler to provide fire-retardancy; and d. at least one catalyst for curing the epoxide-containing resin; and ii. a fibrous reinforcement at least partially impregnated by the epoxy resin matrix.