Composite Foam Midsole Resilience and Delamination
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Solution Overview
Problem
Conventional polymer foams used in midsoles of performance athletic footwear suffer from reduced resilience and increased compression set over time, leading to mechanical failure due to insufficient bonding at the interface between different polymer components, resulting in delamination and degranulation during flexing and wear.
Innovation Solution
A composite foam composition is developed using expanded thermoplastic elastomers, such as eTPEE and eTPEA, embedded within a polyurethane matrix, which enhances interfacial bond strength and maintains desirable properties like resilience and wear resistance without compromising other characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymer foam materials are used in midsole construction, then cushioning and motion control are provided through compression and resiliency, but the foam suffers from reduced resilience and increased compression set over time leading to mechanical failure
Solution Approach 1:
The patent applies composite materials by combining thermoplastic elastomer particles with a polyurethane foam matrix. This composite structure allows the midsole to maintain resilience and resist compression set over time, solving the problem of mechanical failure in conventional single-material foams. The thermoplastic elastomer particles act as reinforcement within the foam matrix, preserving structural integrity and elastic properties during repeated flexing and wear.
Solution Approach 2:
The patent changes the material parameters by selecting specific thermoplastic elastomers with glass transition temperatures below -50°C and melting points above 100°C. These parameter specifications ensure the particles remain flexible at body temperature while maintaining structural stability during curing and wear, thereby improving long-term resilience and reducing compression set.
2Strength
If conventional polymer foam materials are used in midsole construction, then cushioning is provided through open or closed cells displaced by gas, but the foam exhibits delamination and degranulation during flexing and wear due to insufficient bonding at the interface
Solution Approach 1:
The composite structure of thermoplastic elastomer particles embedded in a polyurethane foam matrix creates strong interfacial bonding. The thermoplastic elastomer particles bond chemically and mechanically to the foam matrix, preventing delamination and degranulation that occur in conventional homogeneous foams. This composite approach strengthens the interface between different material phases, eliminating the harmful separation effects during flexing and wear.
Solution Approach 2:
The patent applies local quality by distributing thermoplastic elastomer particles throughout the foam matrix at a concentration of 5-50% by weight. This localized reinforcement at the micro-level creates regions of enhanced bonding strength throughout the midsole structure, preventing delamination without compromising the overall foam cushioning properties.
Data Source
AI summary
Embodiments herein relate generally to the field of footwear, and more particularly to components of performance footwear, such as midsoles, and in particular related to a high performance composite foam for a midsole, the composite foam comprising: a pelletized expanded thermoplastic elastomer; and a polyurethane (PU) matrix, wherein the pelletized expanded thermoplastic elastomer is mixed within the PU matrix. Midsoles made from a high performance composite foam and footwear including such midsoles. A method of making a high performance midsole is also provided.