Recyclable Polymer Foams with Thermoreversible Crosslinking
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Solution Overview
Problem
Existing polymer foams used in midsoles lack high melt strength and thermal stability during the foaming process, leading to cell rupture and poor mechanical properties.
Innovation Solution
Development of thermoreversible crosslinked polymer foams using a maleic anhydride grafted olefin block copolymer (MAH-g-OBC) and a secondary alcohol, which allows for high melt strength, easy processability, and uniform foam structure by forming and breaking crosslinks at different temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional crosslinking is used to achieve high melt strength, then the foam structure is maintained during foaming, but thermal stability issues occur during the foaming process
Solution Approach 1:
The patent employs dynamic crosslinks that can form and break reversibly in response to temperature changes. During foaming at elevated temperatures, the crosslinks break to allow cell expansion and prevent rupture, while upon cooling, they reform to maintain structural integrity. This dynamic behavior resolves the contradiction between needing strength during processing and stability during foaming.
Solution Approach 2:
The invention utilizes temperature-dependent parameter changes in the crosslinking system. The crosslink density and strength vary with temperature, being weaker at high temperatures during foaming and stronger at low temperatures during service. This parameter change allows the material to adapt its properties to different processing and service conditions, simultaneously achieving both melt strength and thermal stability.
2Strength
If high melt strength is required to prevent cell rupture during physical foaming, then foam structure is maintained, but processability is reduced
Solution Approach 1:
The dynamic crosslinking system allows the material to transition between crosslinked and uncrosslinked states during processing. The crosslinks can break under shear stress during mixing and molding operations, improving processability, then reform after processing to provide the necessary melt strength for foam structure maintenance. This dynamic behavior enables both ease of manufacture and structural integrity.
3Ease of repair
If recyclable polymer foams are developed through thermoreversible crosslinking, then ease of recycling is improved, but manufacturing precision may be affected
Solution Approach 1:
The thermoreversible crosslinking system utilizes controlled parameter changes during recycling processes. By carefully controlling temperature and time parameters during reprocessing, the crosslinks can be selectively broken and reformed to maintain uniform foam structure while enabling recyclability. The parameter control ensures that manufacturing precision is preserved even as the material is recycled.
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 foams exhibit superior mechanical performance, processability, and recyclability through hot pressing and physical foaming, maintaining structural integrity and thermal stability.
Implementation Method 1
thermally reversible crosslinking means that the crosslinks dissociate at high temperature and re-associate at room temperature
Implementation Method 2
the crosslinked reaction product of a maleic anhydride grafted olefin block copolymer (MAH-g-OBC) and a secondary alcohol
Implementation Method 3
physical foaming a thermoreversible crosslinkable composition
Data Source
AI summary
Embodiments of the present disclosure are directed to a foam, which may comprise the crosslinked reaction product of a maleic anhydride grafted olefin block copolymer (MAH-g-OBC) and a secondary alcohol. The foam may have a density less than or equal to 0.2 g/cc.