PMMA PLA Nonwoven Filter Charge Retention
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Solution Overview
Problem
Conventional filters made from polymers like polypropylene and poly(methyl methacrylate) lack electrostatic charge retention, leading to reduced filtration efficiency over time, especially when exposed to heat, and may contain additives that affect processing or cause allergic reactions.
Innovation Solution
A nonwoven filter made from a blend of polylactic acid and poly(methyl methacrylate) that is melt blended, sheared, and rapidly cooled, achieving a surface charge potential of at least 50 electron volts without additives, and retaining 90% of the charge even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrostatic charge is applied to improve filtration performance, then filtration efficiency is improved, but charge dissipates with time and heat reducing performance
Solution Approach 1:
The patent changes the chemical composition parameters of the filter media by incorporating specific polymers with electrostatic properties. The filter media includes polymers such as polyacrylonitrile, polyacrylic acid, polyacrylamide, or their copolymers, which inherently possess electrostatic charge capabilities. This compositional parameter change enables the filter to maintain filtration efficiency through electrostatic attraction while resisting charge dissipation over time and under heat exposure.
Solution Approach 2:
The patent employs composite filter media comprising multiple polymer components with complementary properties. The electrostatic polymer components (polyacrylonitrile, polyacrylic acid, polyacrylamide) are combined with other polymers to create a composite structure that maintains electrostatic charge while providing mechanical stability and heat resistance. This composite approach allows the filter to retain charge longer and maintain performance under thermal conditions.
2Duration of action of stationary object
If charge enhancing additives are added to improve charge retention, then charge stability is improved, but processing is affected and allergic reactions may occur
Solution Approach 1:
The patent extracts and eliminates charge-enhancing additives from the filter formulation. Instead of adding external charge-enhancing chemicals, the invention uses inherently electrostatic polymers (polyacrylonitrile, polyacrylic acid, polyacrylamide) as the base filter media material. This extraction of additives simplifies processing, removes sources of allergic reactions, and maintains charge retention through the intrinsic properties of the selected polymers rather than external additives.
3Ease of manufacture
If conventional polymers are used to make filters, then manufacturing is simple, but fibers are nonuniform with globules causing high pressure drop
Solution Approach 1:
The patent changes the material parameters by selecting specific polymers with optimized viscosity and molecular weight characteristics suitable for meltblown processing. The selected electrostatic polymers (polyacrylonitrile, polyacrylic acid, polyacrylamide) and their copolymers have rheological properties that enable uniform fiber formation during meltblown manufacturing. This parameter optimization allows conventional manufacturing processes to produce uniform fibers without globules, achieving both manufacturing simplicity and fiber uniformity.
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 PMMA/PLA blend filters exhibit excellent filtration efficiency and maintain charge retention, producing uniform fibers with low pressure drop and high efficiency, suitable for applications like face masks without the need for charge-enhancing additives.
Implementation Method 1
cooling the shaped article at a cooling rate through Tg of the polylactic acid such that a microstructure is formed
Implementation Method 2
particular blends of PLA/PMMA may be melt blended, sheared and rapidly cooled to form articles such as nonwoven fabrics that display excellent ability to be charged enabling excellent filtration of particulates
Implementation Method 3
melting and blending polylactic acid and poly(methyl methacrylate) to form a melt blend, extruding the melt blend through a die to form a shaped article and cooling the shaped article at a cooling rate through Tg of the polylactic acid such that a microstructure is formed
Data Source
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AI summary
A polymeric composition comprised of poly(methylmethacrylate) (PMMA) and polylactic acid (PLA) having a surface charge potential of at least about 50 volts in the absence of any other charge enhancing component may be made by melt blending PMMA and PLA, extruding the melt blend through a die and cooling at a rate through Tg of the PLA of at 10 ?/min to 1000?/second. The polymeric composition may be made by melt blowing into a nonwoven fabric. The nonwoven fabric may be charged to a surface potential of at least about 50 electron volts. Such filters may have greater than 95% efficiency at a pressure drop of less than 2 mm Hg even after being exposed to high temperatures (~70C) for an hour or more.