Open Cell Foam Sheets via Segmented Compression and Cross-Linking
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Solution Overview
Problem
Existing open cell foam manufacturing technologies face issues with inconsistent cell structure, weak structural form, uneven cell sizes, poor fluid retention, and limited industrial use due to variability in cell geometry and the use of inflammable chemicals, leading to difficulties in achieving consistent absorptivity, compression set, tensile strength, and shear strength.
Innovation Solution
A continuous method involving the formation of closed cell foam sheets through controlled temperature and pressure, followed by compression to convert closed cells into open cells, ensuring consistent cell geometry and cross-linked walls, allowing for uniform fluid flow and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional extrusion method with blowing agent is used to create open cell foam, then cell formation occurs, but cell structure becomes inconsistent and uneven between interior and surface portions
Solution Approach 1:
The process segments cell formation into two distinct stages: first forming closed cells uniformly throughout the foam sheet, then selectively rupturing interior cells to create open cell structure. This segmentation allows each stage to be optimized independently, achieving both uniform cell geometry and consistent open cell structure throughout the product.
Solution Approach 2:
The method performs preliminary formation of closed cells with consistent geometry before converting them to open cells. By first establishing a uniform closed cell structure and then selectively rupturing interior cells, the process ensures that both surface and interior portions achieve consistent open cell characteristics.
2Strength
If cross linking agent is used to strengthen cell walls, then structural strength improves, but cell structure becomes more closed and inter-connectivity decreases
Solution Approach 1:
The process separates cross-linking and cell rupture operations into distinct stages. Cross-linking is performed first to strengthen cell walls, then interior cells are ruptured to create open cell inter-connectivity. This segmentation allows both strong cell walls and open cell structure to coexist in the final product.
3Ease of manufacture
If inflammable chemical blowing agents are used for foam formation, then cell expansion is achieved, but product safety and environmental compatibility deteriorate
Solution Approach 1:
The invention changes the chemical parameter of the blowing agent from inflammable chemicals to supercritical carbon dioxide. This parameter change maintains the foam formation capability while eliminating flammability and toxicity concerns, improving product safety and environmental compatibility.
4Manufacturing precision
If pressure drop across extruder die is increased to create open cells, then open cell structure forms, but cell size variability increases
Solution Approach 1:
The process segments cell structure creation into two controlled stages: first forming uniform closed cells under controlled pressure, then selectively rupturing interior cells. This segmentation eliminates the cell size variability caused by high pressure drops in conventional single-stage processes.
Solution Approach 2:
The method preliminarily forms closed cells with consistent size and geometry before converting them to open cells. This preliminary action establishes a uniform base structure that ensures consistent cell size throughout the final open cell foam product.
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 method produces open cell foam sheets with consistent porosity, fluid retention, and enhanced structural strength, enabling their use in filtration and fluid absorption applications by maintaining uniform cell dimensions and wall strengths across the sheet thickness.
Implementation Method 1
the composition is admixed with a supercritical fluid at conditions sufficient to enable the supercritical fluid to act as a blowing agent
Implementation Method 2
it is suitably expelled from the extruder through a conventional dye under conditions that involve a sudden and significant drop in pressure sufficient to enable the blowing agent to expand and to form voids or closed cells
Implementation Method 3
the composition is maintained under conditions that enable the cross linking agent to convert at least a portion of the thermoplastic olefin polymer into a cross linked material that has substantially stronger cell walls
Implementation Method 4
As the blowing agent expands to create voids or closed cells within the extrudate, the entire composition expands and cools whereby trapping the closed cell voids within the polymer composition resulting in a significant reduction in the overall bulk density of the mixture
Data Source
AI summary
A foam form sheet material having a first large surface comprising substantially only closed cells and an opposite large surface and an interior comprising substantially only open cells. This material comprises a cross linked olefin thermoplastic polymer or copolymer. The foam is made by mixing the polymer with a blowing agent and a cross linking agent. The mixture is maintained in a two roll mill means for a time sufficient to initiate cross linking and to initiate foaming to form closed cells. The sheet material is then disposed in a second two roll mill means having a nip that is larger than the thickness of the foamed sheet material and maintained under elevated temperature and pressure sufficient to initiate further cross linking and foaming. The fully cross linked cell foam is then compressed to rupture the closed cells that are disposed in the interior to form open cells.