Low Density Foam via Supercritical Fluid Foaming
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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 use of a supercritical fluid and up to 15% by weight of a physical or chemical blowing agent to foam thermoplastic polyurethane elastomers or ethylene-vinyl acetate copolymers, allowing for the production of low density foamed articles with densities as low as 0.15 g/cm³, suitable for applications like footwear components and cushioning materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If thermoplastic elastomers are used to produce foams, then the foams have good resiliency and high energy return, but the density of the foams becomes higher than desirable
Solution Approach 1:
The patent changes the physical state and properties of the blowing agent by using supercritical carbon dioxide instead of conventional gaseous or liquid blowing agents. This parameter change allows the foam to achieve lower density (0.04-0.15 g/cm³) while maintaining the resiliency and energy return characteristics of thermoplastic elastomers, thus resolving the contradiction between energy return and density
Solution Approach 2:
The patent creates a composite system by combining thermoplastic elastomer with supercritical carbon dioxide and conventional blowing agents in specific proportions. This composite approach allows the foam to benefit from both the resiliency of the thermoplastic elastomer and the low density achieved through supercritical fluid foaming, simultaneously achieving high energy return and low density
2Device complexity
If conventional blowing agents are used alone, then the foaming process is simpler, but the achieved density is higher than the desirable low density range
Solution Approach 1:
The patent merges supercritical carbon dioxide with conventional blowing agents (physical or chemical) in a dual-blowing agent system. This combination allows the process to maintain relative simplicity while achieving superior low density results (0.04-0.15 g/cm³) that neither system could achieve alone, thus resolving the contradiction between process simplicity and achieving low density
3Strength
If higher density foams are produced, then the structural integrity is maintained, but the weight and suitability for cushioning applications decreases
Solution Approach 1:
By changing to supercritical carbon dioxide as the primary blowing agent, the patent achieves a dramatic reduction in foam density (0.04-0.15 g/cm³) while the thermoplastic elastomer matrix maintains structural integrity. This parameter change in the blowing agent system allows weight reduction without sacrificing the structural properties needed for cushioning applications
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 effectively reduces the density of foamed thermoplastic elastomer articles to desirable levels, enhancing their suitability for applications requiring lightweight yet resilient properties.
Implementation Method 1
foaming a thermoplastic polyurethane elastomer or a thermoplastic ethylene-vinyl acetate copolymer using a supercritical fluid
Implementation Method 2
The thermoplastic elastomer is combined with up to 15% by weight, based on polymer weight, of a physical or chemical blowing agent other than a supercritical fluid
Implementation Method 3
The thermoplastic elastomer is combined with up to 15% by weight, based on polymer weight, of a physical or chemical blowing agent other than a supercritical fluid
Implementation Method 4
the mold contains 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 a combination of a supercritical fluid and a non-supercritical fluid blowing agent.