Recyclable Polymer Foams With Thermoreversible MAH-g-OBC Crosslinks
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Solution Overview
Problem
Existing polymer foams used in footwear 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 through thermally reversible crosslinking.
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 deteriorates during the foaming process
Solution Approach 1:
The patent changes the chemical nature of crosslinks from permanent covalent bonds to reversible hydrogen bonds, which can dynamically break and reform. This parameter change allows the material to exhibit high melt strength at processing temperatures through reversible crosslinking, while maintaining thermal stability as the crosslinks can re-establish after thermal exposure
Solution Approach 2:
The patent introduces dynamic, thermoreversible crosslinks that can break and reform in response to temperature changes. During foaming, the crosslinks dynamically adjust - breaking when needed to allow cell expansion and reforming to maintain structure - providing both high melt strength and thermal stability throughout the process
2Strength
If high melt strength is achieved through crosslinking, then foam structure is maintained, but processability worsens due to permanent crosslinked network
Solution Approach 1:
The thermoreversible crosslinks provide dynamic control over material properties. During processing, the crosslinks can break to allow flow and shaping, improving processability. After processing, the crosslinks reform to provide the necessary melt strength and structural integrity, eliminating the trade-off between these properties
3Ease of manufacture
If thermoreversible crosslinking is used, then processability and recyclability improve, but melt strength may deteriorate at high temperature
Solution Approach 1:
The thermoreversible crosslinks exhibit periodic breaking and reforming behavior in response to temperature cycles. During processing at elevated temperatures, the crosslinks periodically break to enable flow and shaping. Upon cooling, they reform to restore melt strength, creating a periodic cycle that alternates between processability and structural integrity
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, maintaining structural integrity and thermal stability, with densities less than 0.2 g/cc and recyclable through hot pressing and physical blowing.
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, which takes place near the melting point of the polymer
Implementation Method 4
the foam has a density less than or equal to 0.2 g/cc
Data Source
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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.