Foamed Thermoplastic Elastomer Articles Using Supercritical Fluid Nitrogen
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Solution Overview
Problem
Thermoplastic elastomers typically produce foams of higher density, which is not desirable for applications requiring low density and high energy return, such as cushioning materials.
Innovation Solution
A method involving the combination of molten thermoplastic polyurethane elastomer or ethylene-vinyl acetate copolymer with supercritical fluid nitrogen and carbon dioxide to achieve low density foamed articles, with optional addition of up to 15% physical or chemical blowing agents, and using a porous tool in the mold to absorb generated gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermoplastic elastomers are used to make foamed articles, then the articles are recyclable and have good processability, but the density of the foamed articles is higher than desirable
Solution Approach 1:
The patent changes the physical state of the blowing agent to supercritical fluid, which allows for much lower foam density (0.15-0.45 g/cm³) while maintaining thermoplastic elastomer benefits. The supercritical state enables better gas distribution and cell formation control.
Solution Approach 2:
The patent uses a composite approach by combining thermoplastic elastomer with supercritical blowing agents (CO2 and N2), creating a multi-component system that achieves both low density and recyclability. The porous tool insert also adds a structural component for gas management.
2Ease of manufacture
If conventional blowing agents are used, then the foaming process is simple, but the energy return and cushioning properties are insufficient
Solution Approach 1:
The patent changes the blowing agent state to supercritical, which improves energy return and cushioning properties while maintaining processability. The supercritical state allows for better cell structure formation that enhances elastic recovery.
Solution Approach 2:
The porous tool insert acts as an intermediary that absorbs excess gas during foaming, controlling cell structure and improving the foam's energy return properties. This mediator enables better cushioning performance.
3Shape
If gas is generated during foaming, then the foam structure forms, but gas absorption capability is limited without special tools
Solution Approach 1:
The patent introduces a porous tool insert that provides controlled porosity for gas absorption. This porous structure manages the gas generated during foaming, improving foam quality and reducing defects.
Solution Approach 2:
The porous tool insert serves as a mediator between the molten polymer and the generated gas, absorbing excess gas and controlling foam cell formation. This intermediary component resolves the gas management issue.
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 results in foamed articles with densities as low as 0.15 g/cm³, suitable for applications like footwear components and protective gear, offering improved cushioning with reduced weight.
Implementation Method 1
combining a molten thermoplastic polyurethane elastomer or a thermoplastic elastomer ethylene-vinyl acetate copolymer with supercritical fluid nitrogen and supercritical fluid carbon dioxide
Implementation Method 2
The mold may contain a porous tool for absorbing gas generated during foaming of the molded article
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
Foamed thermoplastic elastomeric polyurethane and ethylene-vinyl acetate copolymer articles are made with from about 0.1 to about 4 weight percent of supercritical fluid nitrogen based on polymer weight and from about 0.1 to about 5 weight percent of a supercritical fluid carbon dioxide based on polymer weight, with the supercritical fluid nitrogen and the supercritical fluid carbon dioxide being separately added to the molten polymer.