Fire Resistant Wallboard with Carbon Black and Expandable Graphite
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Solution Overview
Problem
Conventional gypsum wallboards face challenges in maintaining structural integrity and preventing heat transfer during high-temperature exposure, leading to failure in fire resistance tests due to shrinkage and inadequate insulation.
Innovation Solution
The use of a combination of expandable graphite and carbon black in the gypsum wallboard construction, where carbon black is dispersed just below the face paper and expandable graphite is dispersed throughout the gypsum core, mitigates heat transfer and shrinkage by providing thermal insulation and counterbalancing shrinkage through expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If vermiculite is incorporated into the gypsum core to mitigate shrinkage, then structural integrity is improved, but thermal insulation performance is insufficient
Solution Approach 1:
The patent combines vermiculite with graphite particles and carbon black to create a composite material system. The vermiculite provides shrinkage mitigation through expansion, while the graphite and carbon black components enhance thermal insulation performance, resolving the contradiction between structural integrity and heat transfer resistance.
Solution Approach 2:
The patent applies different materials to different regions of the wallboard core. Carbon black is concentrated near the face paper to provide localized thermal insulation at the fire-exposed surface, while vermiculite is distributed throughout the core for shrinkage compensation, optimizing both functions in their respective locations.
2Stability of the object's composition
If vermiculite is used to expand and counterbalance shrinkage, then board stability is improved, but thermal insulation is inadequate
Solution Approach 1:
The invention creates a composite system where vermiculite particles are combined with graphite and carbon black. The vermiculite maintains board stability through expansion during heating, while the graphite and carbon black components provide enhanced thermal insulation, addressing both stability and energy loss resistance simultaneously.
Solution Approach 2:
The patent utilizes the change in physical parameters of vermiculite during heating - its expansion ratio increases dramatically (up to 300%) when exposed to fire temperatures. This parameter change allows the vermiculite to counterbalance shrinkage while the combined material system maintains thermal insulation performance.
3Loss of energy
If gypsum undergoes dehydration reaction to release water molecules, then heat transfer is temporarily insulated, but board shrinkage occurs
Solution Approach 1:
The patent applies thermal expansion principles by incorporating vermiculite, graphite, and carbon black materials that expand when heated. This expansion counteracts the shrinkage caused by gypsum dehydration, maintaining the board's dimensional stability while the dehydration process continues to provide thermal insulation through water molecule release.
Solution Approach 2:
The expanding vermiculite particles act as a counterweight to the shrinkage force generated by gypsum dehydration. As the vermiculite expands up to 300% of its original volume, it provides an opposing force that balances the contraction of the gypsum core, preventing net shrinkage of the wallboard.
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
This solution achieves superior performance in reducing shrinkage and prolonging the time to reach high temperatures, compared to traditional systems containing vermiculite alone, thereby enhancing the fire resistance of gypsum wallboards.
Implementation Method 1
a small quantity of carbon black is dispersed in the layer of gypsum just below the face paper... the thermal insulation provided by the carbon black layer
Implementation Method 2
a small quantity of expandable graphite is dispersed in the rest of the gypsum core... When heated, the expandable graphite particles expand as much as 1000-fold... the expansion of expandable graphite has shown results that are superior to traditional systems containing vermiculite alone
Implementation Method 3
the gypsum (calcium sulfate dihydrate) that makes up the wallboard's core undergoes a dehydration reaction which first converts gypsum to calcium sulfate hemihydrate and then to calcium sulfate. This series of reactions involve the release of water molecules which help to temporarily insulate the wallboard and slow the transfer of heat
Data Source
AI summary
A fire resistant wallboard with carbon black and expandable graphite. A carbon black layer is positioned between the conventional cover sheet and a gypsum core with embedded expandable graphite. The carbon black layer may be employed either with one of the cover sheets or with both of the cover sheets.