Open-Cell Ethylenic Foam Backer Rods for Outgassing Control
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Solution Overview
Problem
Standard backer rods made from closed-cell polyethylene foam experience outgassing issues due to trapped gases, leading to seal integrity problems and compromised performance under ambient conditions, which existing technologies have not adequately addressed.
Innovation Solution
A method involving the extrusion of a foamable polyethylene composition with a subsequent compression step to increase open-cell content to 86-98% by volume, combined with an external impervious skin, effectively reducing outgassing and enhancing seal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If closed-cell polyethylene foam is used for backer rods, then the foam provides structural integrity and compression resistance, but trapped gases escape through the sealant causing outgassing and seal failure
Solution Approach 1:
The patent applies porous materials by transforming the closed-cell foam structure into an open-cell foam structure with 30-85% open cells. This porous structure allows trapped gases to escape through the foam matrix itself rather than forcing them through the sealant, thereby eliminating outgassing while maintaining compression resistance through the foam's inherent cellular structure
Solution Approach 2:
The patent converts the harmful trapped gases into a beneficial flow path by creating open cells that channel gas escape through the foam. The previously harmful outgassing phenomenon is transformed into a controlled internal flow that protects the sealant from degradation
2Object-generated harmful factors
If open-cell content is increased to reduce outgassing, then gas flow through foam is improved, but foam structural integrity and compression properties deteriorate
Solution Approach 1:
The patent applies parameter changes by optimizing the open-cell content to a specific range of 30-85%, rather than using extreme open or closed cell structures. This parameter optimization balances gas flow capability with structural integrity, achieving outgassing reduction while maintaining sufficient compression resistance for backer rod functionality
Solution Approach 2:
The patent creates a composite foam structure that combines open-cell and closed-cell characteristics within the same foam matrix. This composite structure allows regions of open cells to facilitate gas escape while other regions maintain the compression resistance needed for structural support
3Shape
If extrusion temperature is increased to achieve high open-cell content, then foam structure is improved, but energy consumption and material degradation increase
Solution Approach 1:
The patent applies parameter changes by utilizing the foamable composition's inherent foaming characteristics that activate at moderate extrusion temperatures. This allows achievement of high open-cell content (30-85%) without requiring excessive thermal energy input, avoiding both energy waste and polymer degradation that would occur at much higher temperatures
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 significantly reduces outgassing, maintaining seal integrity and performance by allowing internal air-flow through open cells while preserving the external skin's integrity, thus improving the compressibility and resilience of backer rods.
Implementation Method 1
extruding the foamable polyethylene composition through the extruder at an elevated temperature to form an extruded foam rod or extruded foam ribbon
Implementation Method 2
The presence of open cells in the foam substantially reduces outgassing by enabling internal air-flow
Data Source
AI summary
An extruded, low-density, ethylenic polymer foam including from about 86% by volume to about 98% by volume open cells and a continuous, impervious surface skin is disclosed. The foam possesses superior compression recovery and lower compression resistance when compared with similarly comprised ethylenic closed-cell foams and superior moisture resistance and handling characteristics when compared to open-cell foams. A precursor composition and method for making the extruded, low-density, ethylenic polymer foam are also disclosed.