Polymeric Foam Shoe Soles for Compression Set Resistance
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Solution Overview
Problem
Existing shoe soles, particularly those made from Ethylene-Vinyl Acetate (EVA) foam, suffer from rapid 'compression set' and loss of resilience over time, leading to reduced durability and frequent replacement, which is environmentally unsustainable.
Innovation Solution
A polymeric foam compound comprising 28% to 32% organic polymer, 38% to 40% Ethylene Vinyl Acetate (EVA), 21% to 25% Olefin Block Copolymer (OBC), 7% to 10% BIIR-Butyl rubber, and 0.025% to 0.25% Graphene-based material, optimized for improved durability and resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EVA foam is used for midsoles, then durability and flexibility are improved, but compression set resistance deteriorates
Solution Approach 1:
The patent uses a composite material system consisting of EVA foam combined with butyl rubber and organic polymer in specific proportions (EVA: 38-40%, butyl rubber: 7-10%, organic polymer: 28-32%). This composite formulation leverages the complementary properties of each component: EVA provides flexibility and cushioning, butyl rubber enhances compression set resistance through its molecular structure, and the organic polymer adds durability. The synergistic combination resolves the contradiction by achieving both durability and compression set resistance simultaneously.
Solution Approach 2:
The patent optimizes the compositional parameters of the foam compound by precisely controlling the weight percentages of each component within specific ranges. Additionally, the foam density is controlled at 0.22-0.26 g/cm³, and the acetate content in EVA is maintained at 18-30%. These parameter optimizations ensure the material achieves the desired balance between durability and compression set resistance, transforming the trade-off into a controlled performance profile.
2Weight of moving object
If EVA foam density is reduced, then weight is reduced, but mechanical strength deteriorates
Solution Approach 1:
The composite formulation incorporates butyl rubber (7-10%) and organic polymer (28-32%) alongside EVA, creating a reinforced foam structure. The butyl rubber contributes to structural integrity through its elastomeric properties, while the organic polymer enhances overall mechanical strength. This composite approach allows the foam to maintain low density (0.22-0.26 g/cm³) for weight reduction while the synergistic material combination compensates for the strength typically lost at lower densities.
Solution Approach 2:
The patent creates local quality variations within the foam structure through the distributed network of closed cells and the specific arrangement of polymer chains. The heterogeneous microstructure, with cells averaging 0.1 mm in diameter, provides localized load-bearing regions that maintain mechanical strength despite the overall low density. This local structural optimization allows different regions of the material to perform different functions, balancing weight and strength requirements.
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 compound significantly reduces compression set and enhances resilience, maintaining mechanical properties over time, thus extending the shoe's lifespan and reducing environmental impact.
Implementation Method 1
the impact force transmitted from the ground through the shoe and into the feet and legs of the user is believed to be one of the leading causes of foot injuries
Implementation Method 2
one of the most important mechanical properties of performance footwear is its damping (cushioning) and rebound (energy return) behaviour
Implementation Method 3
optimised damping and rebound characteristics of the shoe can provide protection to the soft tissue of the human foot, as well as, support the involved muscle groups
Implementation Method 4
rebound (energy return) behaviour
Implementation Method 5
Compression set is understood as a thinning of an elastomeric foam material that is caused by excessive compression forces being placed repetitively on that material over time
Data Source
AI summary
The present invention provides for a sole for a footwear article, said sole is formed from a polymeric foam compound comprising: 28% to 32% by weight of an organic polymer; 38% to 40% by weight of Ethylene Vinyl Acetate (EVA); 21% to 25% by weight of an Olefin Block Copolymer (OBC); 7% to 10% by weight of BIIR-Butyl rubber, and 0.025% to 0.25% by weight of a Graphene-based material having lateral dimension in the region of 1 μm to 10 μm and a thickness in the region of 5 nm to 10 nm.