Thermoplastic Polyurethane Foam Beads Density Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thermoplastic elastomers typically produce foams of higher density than desired for certain applications, which can compromise the resilience and durability required for cushioning materials.
Innovation Solution
A method involving the use of thermoplastic polyurethane foam beads with a density of 0.01 to 0.3 g/cm³, combined with a mixture of thermoplastic polyurethane elastomer or ethylene-vinyl acetate copolymer, a supercritical fluid, and up to 15% by weight of a physical or chemical blowing agent, to create a low-density foamed article with densities as low as 0.2 g/cm³, suitable for applications like footwear components and protective gear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermoplastic elastomers are used to produce foams, then the foams have good resilience and durability, but the density is higher than desired for certain applications
Solution Approach 1:
The patent uses a composite material system consisting of thermoplastic polyurethane elastomer combined with supercritical fluid and physical/chemical blowing agents. This composite approach allows the foam to maintain the resilience and durability of thermoplastic elastomers while incorporating gas phases that reduce overall density to desired levels for cushioning applications
Solution Approach 2:
The patent utilizes phase transitions of supercritical fluid and blowing agents during the foaming process. The supercritical fluid and blowing agents undergo phase changes from liquid/gas to gas bubbles within the polymer matrix, creating a cellular foam structure that reduces density while preserving the mechanical properties of the thermoplastic elastomer base material
2Ease of manufacture
If only supercritical fluid is used for foaming, then the process is simple, but the achieved density is not low enough for certain applications
Solution Approach 1:
The patent merges multiple blowing mechanisms by combining supercritical fluid with physical blowing agents and/or chemical blowing agents in a single foaming process. This combination allows the synergistic effect where supercritical fluid provides initial cell nucleation and expansion, while physical/chemical blowing agents contribute additional gas volume, achieving lower densities than any single agent could produce alone
3Quantity of substance
If physical or chemical blowing agents are used alone, then the density can be reduced, but the process becomes less efficient compared to supercritical fluid alone
Solution Approach 1:
The patent applies preliminary action by incorporating the blowing agents and supercritical fluid into the polymer matrix before the actual foaming occurs during molding. The extrusion process pre-mixes the thermoplastic polyurethane elastomer with blowing agents and supercritical fluid under controlled conditions, ensuring uniform distribution before injection into the mold where foaming is triggered by heat and pressure release, thereby improving overall process efficiency
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 achieves a significantly lower density in foamed articles, enhancing their cushioning properties while maintaining durability, making them suitable for various applications including footwear and protective gear without excessive weight.
Implementation Method 1
a supercritical fluid, and up to 15% by weight, based on polymer weight, of a physical or chemical blowing agent other than a supercritical fluid
Implementation Method 2
foaming in the mold a mixture of thermoplastic polyurethane elastomer or a thermoplastic elastomer ethylene-vinyl acetate copolymer, a supercritical fluid
Implementation Method 3
The mold may contain a porous tool for absorbing gas generated during foaming of the thermoplastic polyurethane or EVA elastomer
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A method for making a low density foamed article includes placing a desired amount of thermoplastic polyurethane foam beads in a cavity of an injection mold (28) and closing the mold; combining in an extruder (12) connected to the mold a molten polymer selected from the group consisting of thermoplastic polyurethane elastomers and thermoplastic ethylene-vinyl acetate copolymers with both a physical or chemical blowing agent other than a supercritical fluid present in an amount up to about 15 wt% based on molten polymer weight and a supercritical fluid that is at least one of about 0.1 to about 5 weight percent of supercritical CO2 based on molten polymer weight or about 0.1 to about 4 weight percent of supercritical N2 based on molten polymer weight, to form a mixture and injecting the mixture into the mold and foaming the mixture to form the low density foamed article.