Polyethylene Membrane Blend for Strength and Gel Extrusion
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Solution Overview
Problem
High molecular weight polyethylene polymers exhibit reduced flowability in the molten state, making conventional processing techniques like melt extrusion challenging, and existing polyethylene membranes lack optimal mechanical properties such as puncture strength and tensile strength for battery separator applications.
Innovation Solution
A polymer composition blend of three different polyethylene polymers with varying molecular weights, combined with a plasticizer, is used to form gel-extruded articles like membranes, which are then processed to enhance mechanical properties and porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight polyethylene polymers are used to improve mechanical properties, then puncture strength and tensile strength are improved, but flowability in the molten state deteriorates
Solution Approach 1:
The patent applies parameter changes by blending polyethylene polymers with different molecular weights (ranging from 100,000 to 10,000,000 g/mol) to optimize both mechanical strength and flowability. The blend ratio of high molecular weight to low molecular weight polymers is adjusted as a key parameter to achieve the desired balance between puncture strength and processability during gel extrusion.
Solution Approach 2:
The patent uses composite materials by creating a blend of polyethylene polymers with different molecular weight characteristics. This composite approach combines the high strength properties of ultra-high molecular weight polyethylene with the better flow properties of lower molecular weight polyethylene, resulting in a material that exhibits both improved mechanical properties and acceptable processability.
2Strength
If polyethylene polymers with higher molecular weight are used to enhance mechanical properties, then membrane strength is improved, but processing by conventional techniques becomes difficult
Solution Approach 1:
The patent employs an intermediary approach by using gel extrusion as a processing method that bridges the gap between conventional melt extrusion and the requirements for high molecular weight polyethylene. The gel extrusion process uses a solvent medium to enable processing of high molecular weight polymers that would otherwise be too viscous for conventional melt processing, while still producing membranes with excellent mechanical properties.
3Reliability
If microporous structure is created for ion permeability, then ion permeability is improved, but mechanical strength may be reduced
Solution Approach 1:
The patent applies porous materials principles by creating a microporous structure in the polyethylene membrane through the gel extrusion process. The porous structure is formed by the removal of the solvent used during gel extrusion, leaving behind a controlled network of micro-pores that enable ion permeability while the surrounding polymer matrix maintains mechanical integrity.
Solution Approach 2:
The patent uses composite materials to balance porosity and strength by combining the microporous structure with high molecular weight polyethylene blend. The composite structure allows the porous regions to provide ion transport pathways while the denser polymer regions provide mechanical support, achieving both ion permeability and adequate mechanical strength.
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 blended polyethylene membranes exhibit improved puncture strength, pin strength, and tensile strength, with increased processability, making them suitable for battery separators with enhanced safety features.
Implementation Method 1
The polymer composition contains a blend of different polymers, such as at least three different polyethylene polymers, that when blended together produce an excellent combination of mechanical and physical properties
Implementation Method 2
The polymer composition of the present disclosure contains a plasticizer in combination with polymer particles
Implementation Method 3
the microporous membrane permits ions to pass through due to the porous nature of the material
Implementation Method 4
The shutdown effect refers to the self-closing of micro-pores within the polyethylene separator when it surpasses a certain temperature
Data Source
AI summary
A polymer composition for producing gel extruded articles is described. The polymer composition contains at least three different polyethylene polymers, namely a lower molecular weight polyethylene polymer, a mid-range molecular weight polyethylene polymer, and a high molecular weight polyethylene polymer. Combining the different polyethylene polymers in different ratios can optimize not only mechanical properties but improve processing.