Polyethylene Membrane Blend for Strength and Extrusion Flow
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Solution Overview
Problem
High molecular weight polyethylene polymers exhibit decreased flowability in the molten state, making conventional processing methods 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 decreases
Solution Approach 1:
The patent divides the polymer system into multiple segments with different molecular weights (first, second, and third polyethylene polymers). This segmentation allows each component to contribute different properties: lower molecular weight polymers provide flowability while higher molecular weight polymers provide mechanical strength, resolving the contradiction between processability and mechanical performance.
Solution Approach 2:
The patent changes the molecular weight parameter by using a distribution of different molecular weights rather than a single value. This parameter change enables the polymer blend to exhibit both good flow characteristics (from lower MW components) and high mechanical strength (from higher MW components), simultaneously addressing both requirements.
2Ease of manufacture
If polyethylene polymers are processed by conventional melt extrusion, then processing is simplified, but high molecular weight polymers with decreased flowability cannot be effectively processed
Solution Approach 1:
The patent introduces a plasticizer as an intermediary substance that facilitates the processing of high molecular weight polyethylene polymers. The plasticizer acts as a mediator between the polymer and the processing equipment, enabling conventional melt extrusion to effectively process high MW polymers that would otherwise be too viscous, while the plasticizer is subsequently removed to leave the desired polymer product.
3Reliability
If microporous membranes are formed through gel-processing, then ion permeability and shutdown effect are achieved, but mechanical properties such as puncture strength and tensile strength need improvement
Solution Approach 1:
The patent creates a composite polymer system blending multiple polyethylene polymers with different molecular weights. This composite approach allows the membrane to maintain the microporous structure necessary for ion permeability and shutdown effect while the higher molecular weight components provide enhanced mechanical strength, simultaneously achieving both functional and mechanical requirements.
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 polymer membranes exhibit improved puncture strength, pin strength, and tensile strength, making them suitable for battery separators with enhanced safety features.
Implementation Method 1
The resultant gel is extruded into a fiber or membrane
Implementation Method 2
the microporous membrane permits ions to pass through due to the porous nature of the material
Implementation Method 3
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.