Intumescent Backer Rod Fire Barrier Design
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Solution Overview
Problem
Conventional backer rods used in construction joints lack fire-resistant properties, as they do not effectively prevent the spread of fire between building elements, especially when exposed to high temperatures, and existing fire-resistant materials like slag mineral wool or ceramic fibers are not suitable for all applications.
Innovation Solution
A construction assembly featuring an elongated tube made of combustible foam plastic with an intumescent core that expands significantly when exposed to fire, forming a fire-resistant barrier within the joint space, thereby preventing fire spread.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional closed-cell polyethylene foam backer rod is used, then ease of manufacture and installation are improved, but fire resistance is insufficient as the material cannot withstand high temperatures required by fire-resistant rated joints
Solution Approach 1:
The backer rod is constructed as a composite material system combining polyethylene foam (combustible, easy to manufacture) with intumescent additives (fire-resistant). The composite structure allows the material to maintain ease of manufacture while gaining fire-resistant properties through the chemical reaction of intumescent compounds when exposed to fire temperatures.
Solution Approach 2:
The backer rod material undergoes parameter changes when exposed to fire - the intumescent additives trigger a chemical reaction that causes volumetric expansion (10-50 times original volume) and formation of a charred insulating barrier. This parameter change transforms the material from combustible to fire-resistant state during fire exposure.
2Reliability
If slag mineral wool or ceramic fiber is used to achieve fire resistance, then fire resistance is improved, but adaptability to different construction applications is reduced
Solution Approach 1:
The intumescent backer rod serves multiple functions: it provides fire resistance through intumescent expansion, maintains sealant depth control like conventional backer rods, offers ease of installation due to flexible foam construction, and can be used in various construction joint applications. This multi-functionality makes it adaptable to different construction scenarios while maintaining fire-resistant properties.
3Reliability
If intumescent material is used to provide fire resistance, then fire resistance is improved, but device complexity increases due to the need for combustible foam plastic tube and core structure
Solution Approach 1:
The backer rod employs a nested structure where the intumescent core material is enclosed within a combustible foam plastic tube. The tube provides structural integrity and sealant contact surface, while the core provides fire-resistant expansion capability. This nested arrangement integrates multiple functions into a single composite component, reducing overall system complexity despite the sophisticated internal structure.
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 intumescent backer rod provides effective fire resistance and insulation, maintaining its structure and expanding to fill the joint space, thus impeding fire advancement and meeting industry standards for fire-resistant joint systems.
Implementation Method 1
The core is formed of an intumescent material which is expandable when exposed to fire. The intumescent material has an intumescent expansion factor sufficient to expand to a volume beyond the total assembly volume.
Implementation Method 2
The tube is formed of a first material, and the core is formed of a second material. The first material is a combustible foam plastic which disintegrates when exposed to fire.
Data Source
AI summary
A backer rod adapted for forming a fire-resistant seal within a construction joint. The backer rod may include an elongated tube defining a total assembly volume and a hollow interior, and a core disposed within the hollow interior. The tube is formed of a combustible foam plastic which disintegrates when exposed to fire. The core material is expandable when exposed to fire, such that the core has an intumescent expansion factor sufficient to expand to a volume beyond the total assembly volume. The backer rod may be press fit into a void between two surfaces to a depth. A sealant layer may be formed within the void. When exposed to fire on a side opposite the sealant layer, the external shell disintegrates, the core expands within the void in a direction away from the sealant layer, and a fire-resistant barrier is formed within the void between the surfaces.