Thermoplastic Elastomer Pellet Foaming for Customized Footwear Cushioning
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Solution Overview
Problem
There is a need for improved methods of forming foams that can be customized for cushioning in footwear and protective wear, as existing methods do not allow for sufficient variability in density and composition to meet specific application requirements.
Innovation Solution
The method involves infusing thermoplastic elastomer pellets with a supercritical fluid, followed by rapid depressurization and heating to produce foamed pellets of varying densities, which are then molded into articles with distinct density and composition regions, allowing for customized cushioning and response rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single density foam is used throughout the footwear article, then the manufacturing process is simple, but the cushioning performance cannot be optimized for different regions of the foot
Solution Approach 1:
The footwear article is divided into multiple regions (heel, midfoot, forefoot) with different foam densities. The heel region uses higher density foam for maximum cushioning, while the forefoot uses lower density foam for flexibility and weight reduction. This segmentation allows each region to be optimized for its specific functional requirements.
Solution Approach 2:
Different physical properties (density, hardness, cushioning characteristics) are assigned to different locations within the footwear article. The heel area receives denser, more cushioning-focused foam, while the toe area receives lighter, more flexible foam, creating local quality variations that match the anatomical and functional needs of different foot regions.
2Manufacturing precision
If foam pellets are heated slowly, then the foam expansion is controlled and uniform, but the production time increases
Solution Approach 1:
The heating process uses periodic or cyclic temperature control, where the heating medium temperature is adjusted in stages. Initially, a moderate temperature is applied to allow uniform foam nucleation and expansion, then temperature is increased to complete the expansion and set the foam structure. This periodic heating achieves both uniformity and efficiency.
Solution Approach 2:
The foam expansion process utilizes phase transition of the blowing agent from liquid to gas. By controlling the heating rate and temperature profile, the phase transition occurs in a controlled manner, allowing uniform cell formation and expansion throughout the foam matrix, achieving both precision and reasonable production time.
3Strength
If high density foam is used throughout the footwear article, then structural strength is improved, but weight increases and comfort decreases
Solution Approach 1:
The footwear structure is segmented into high-strength zones (heel, arch support) and low-weight zones (forefoot, toe box). High density foam is strategically placed only where structural support is critical, while lower density foam is used in areas where weight reduction and flexibility are prioritized, achieving overall strength without excessive weight.
Solution Approach 2:
Different density levels are assigned to different anatomical regions based on their specific mechanical requirements. The heel and arch areas receive high density foam for load-bearing and structural support, while the forefoot and toe areas receive low density foam for flexibility and weight reduction, creating local quality optimization.
4Weight of moving object
If low density foam is used throughout the footwear article, then weight is reduced and comfort is improved, but structural integrity and support are compromised
Solution Approach 1:
The footwear is divided into structural support zones and comfort zones. Low density foam is used in comfort zones where weight reduction is beneficial, while high density foam is placed in structural zones where integrity and support are critical, ensuring both weight reduction and structural integrity are achieved through strategic segmentation.
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
This approach enables the creation of foamed articles with tailored density and composition profiles, enhancing cushioning and weight distribution in footwear and protective gear while maintaining structural integrity.
Implementation Method 1
infused with a supercritical fluid in a pressurized container, then rapidly depressurized and heated
Implementation Method 2
rapidly depressurized and heated either by immersion in a heated fluid
Implementation Method 3
heated either by immersion in a heated fluid that can rapidly heat the article or with infrared or microwave radiation
Implementation Method 4
heated either by immersion in a heated fluid that can rapidly heat the article or with infrared or microwave radiation
Implementation Method 5
heated either by immersion in a heated fluid that can rapidly heat the article or with infrared or microwave radiation
Data Source
AI summary
Pellets, beads, particles, or other pieces of a thermoplastic elastomer having a maximum size in at least one dimension of 10 mm or less (collectively, “pellets”) are infused with a supercritical fluid in a pressurized container, then rapidly depressurized and heated either by immersion in a heated fluid or with infrared or microwave radiation to foam the pellets The pellets are prepared with at least two different densities. Pellets with different densities, thermoplastic elastomer compositions, or foam response rates are placed in different areas of a mold. The mold is filled with pellets, then the pellets are molded into a part. The part has areas of different density as a result of the placement of pellets of different density.