Mechanical Devulcanization of Recycled Rubber for Footwear Outsoles
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Solution Overview
Problem
Conventional rubber recycling methods rely on chemical devulcanization, which reduces environmental benefits and results in recycled rubber products with inferior physical properties due to poor bonding with virgin rubber, limiting the recycled content in new products to less than 20% and compromising performance.
Innovation Solution
Mechanical devulcanization using a high-pressure water jet to create recycled rubber particles with a high surface area-to-mass ratio, allowing for blending with virgin rubber at higher loading rates without chemicals, enhancing bonding and physical properties in recycled rubber products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical devulcanization is used to process recycled rubber, then the rubber can be reformed, but the physical properties are much lower than virgin rubber due to poor bonding
Solution Approach 1:
The patent replaces chemical devulcanization processes with a mechanical approach using a hammer mill to grind recycled rubber into particles. This mechanical size reduction enables effective mixing and bonding with virgin rubber in the extrusion process, eliminating the bonding problems associated with chemical devulcanization while maintaining or improving physical properties.
Solution Approach 2:
The patent changes the particle size parameter of recycled rubber by grinding it in a hammer mill to create fine particles. This parameter change increases the surface area and improves the mixing and bonding characteristics with virgin rubber, directly addressing the poor bonding issue that plagues conventional recycled rubber products.
2Loss of substance
If recycled rubber content is increased in new products, then environmental benefits improve, but physical properties deteriorate due to poor bonding
Solution Approach 1:
By replacing chemical devulcanization with mechanical grinding in a hammer mill, the patent enables effective processing of high percentages of recycled rubber (70-100%). The fine particles produced by mechanical size reduction mix and bond properly with virgin rubber during extrusion, allowing high recycled content while maintaining physical properties.
Solution Approach 2:
The patent changes the particle size distribution parameter of recycled rubber through hammer mill grinding, creating a fine particle size that enables effective mixing and bonding at high recycled rubber loadings. This parameter change allows the formulation to achieve both high environmental benefit and acceptable physical properties.
3Ease of manufacture
If chemical devulcanization processes are used, then recycled rubber can be reformed, but environmental advantages are reduced due to added chemicals
Solution Approach 1:
The patent replaces chemical devulcanization processes with a purely mechanical approach using a hammer mill for size reduction. This eliminates the need for additional chemicals in the recycling process, maintaining environmental advantages while still enabling effective recycling and reformulation of rubber products.
Solution Approach 2:
The patent allows recycled rubber to be processed and reused through simple mechanical grinding without requiring chemical treatments. The hammer mill processing and subsequent extrusion enable the recycled rubber to serve itself in creating new products, eliminating the need for external chemical agents and their associated environmental impacts.
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 mechanical devulcanization process enables the production of footwear outsoles with improved tensile strength, elongation, tear resistance, and abrasion properties, allowing for higher recycled content (up to 50%) while maintaining or exceeding industry standards, thus enhancing environmental sustainability and product performance.
Implementation Method 1
mechanically devulcanizing the recycled rubber via a high-pressure water jet to form recycled rubber particles
Implementation Method 2
mechanically devulcanizing the recycled rubber via a high-pressure water jet to form recycled rubber particles with a high surface area-to-mass ratio
Data Source
AI summary
A footwear outsole created partially from a preferred recycled rubber consisting of a rubber powder of a high surface to area to volume ratio. The recycled rubber is created via a fully mechanical process and devulcanized without the use of chemicals. When mixed and re-vulcanized into new rubber, the surface area to volume ratio of the recycled rubber particles produce a rubber that mixes well with virgin rubber and results in a compound with excellent physical parameters. The recycled rubber powder has rubber particles that are preferably of a size between 250 and 1000 micrometers. Consumer products such as footwear outsoles, produced using the preferred recycled rubber mixed with virgin rubber display excellent physical properties for the intended use of footwear outsoles.