Foamed Thermoplastic Polymer Midsole via Crosslinking and Gas Infusion
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Solution Overview
Problem
Current methods for producing foamed articles, such as foamed midsoles for athletic footwear, require higher specific gravities and new molds for each design, limiting design flexibility and efficiency in the foaming process.
Innovation Solution
A method involving milling a block of unfoamed thermoplastic polymer to create a precursor with a cavity, crosslinking the polymer, and infusing it with inert gases to achieve foaming, which can include a second foaming step for further shaping and reducing density, allowing for the incorporation of inserts printed using a 3D printer for customized designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If injection molding is used to produce foamed midsoles, then production efficiency is improved, but the specific gravity must be higher and new molds are required for each design
Solution Approach 1:
The patent changes the physical and chemical parameters of the polymer material, specifically using crosslinking to transform thermoplastic polymer into thermosetting polymer. This parameter change allows the material to foam at lower specific gravities (0.08-0.20) while maintaining structural integrity during injection molding, resolving the contradiction between production efficiency and specific gravity requirements
Solution Approach 2:
The patent utilizes phase transition through crosslinking transformation, where the polymer transitions from thermoplastic to thermosetting state. This phase change enables the material to undergo controlled foaming at lower densities while maintaining the mechanical properties needed for injection molding processes, eliminating the need for higher specific gravities
2Manufacturing precision
If injection molding is used for each new design, then manufacturing precision is improved, but device complexity increases due to requiring new molds
Solution Approach 1:
The patent creates a universal mold that can produce multiple different foamed midsole designs through the flexibility of the foamable precursor material. The crosslinked polymer precursor can be molded into various shapes and then foamed in-situ, allowing a single mold to serve multiple design functions, thereby reducing device complexity while maintaining manufacturing precision
Solution Approach 2:
The patent performs preliminary crosslinking of the polymer before injection molding and foaming. This preliminary chemical action creates a thermosetting precursor that maintains dimensional stability during molding, allowing precise mold designs to be accurately reproduced without requiring multiple specialized molds for different designs
3Adaptability or versatility
If blocks of foam are cut to desired shapes, then design flexibility is improved, but material waste increases
Solution Approach 1:
The patent performs preliminary shaping by milling the foamable precursor to the exact desired geometry before foaming. This preliminary mechanical action creates a precise precursor shape that, when foamed in-situ, produces the final foam article with minimal material waste, eliminating the need to cut and trim foam blocks after foaming
Solution Approach 2:
The patent replaces the mechanical post-foaming cutting and trimming process with in-situ foaming of a pre-milled precursor. Instead of mechanically removing material after foam creation, the system uses controlled chemical foaming of a precisely shaped precursor, substituting mechanical waste-generating operations with a more efficient chemical process
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 production of foamed articles with improved design flexibility, reduced weight, and enhanced cushioning properties while minimizing material waste and the need for multiple molds, allowing for efficient production of foamed components like midsoles and other protective gear.
Implementation Method 1
The precursor and insert are then heated so that the thermoplastic polymer of each is infused with at least one inert gas
Implementation Method 2
the thermoplastic polymer of each is infused with at least one inert gas
Implementation Method 3
The precursor may be milled using a computerized numeric control. The block may be milled into a precursor for a foamed midsole. Before or following milling, the thermoplastic polymer is crosslinked
Implementation Method 4
The precursor and insert are then heated so that the thermoplastic polymer of each is infused with at least one inert gas. Each of the insert and the precursor is independently infused with inert gas below or up to a saturation point
Implementation Method 5
The precursor containing the insert is heated to a first temperature to soften the thermoplastic polymer of the precursor and the thermoplastic polymer of the insert and allow the precursor and the insert to at least partially foam. The thermoplastic polymer may be heated to the first temperature at a first pressure greater than atmospheric pressure, then the pressure may be reduced to a second pressure less than the first pressure to allow the thermoplastic polymer to at least partially foam
Data Source
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AI summary
The present application relates to a method of making a foamed article, comprising milling a block or sheet of thermoplastic polymer to form a precursor; crosslinking the thermoplastic polymer; heating the precursor to a first temperature to soften the thermoplastic polymer; infusing the thermoplastic polymer with at least one inert gas at a first pressure that is sufficient to cause the at least one inert gas to permeate into the softened thermoplastic polymer; and reducing the pressure to a second pressure below the first pressure to at least partially foam the precursor into a foamed article, wherein the foamed article is substantially the same shape as the precursor.