Oleophobic Composite Membrane Coating That Preserves Air Permeability
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Solution Overview
Problem
Porous membranes, such as those made from expanded polytetrafluoroethylene (ePTFE), tend to absorb oils, compromising their hydrophobic and waterproof properties, and existing solutions like hydrophilic coatings can cause discomfort due to moisture retention and lack of air permeability.
Innovation Solution
A composite membrane with a porous base structure coated using a fluorinated acrylate copolymer and isocyanate crosslinker, applied via a low surface tension fluid like supercritical carbon dioxide, which enhances oleophobicity without blocking pores, ensuring air permeability and moisture vapor transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a continuous hydrophilic film is attached to the ePTFE membrane to protect from oil, then oleophobic protection is improved, but air permeability is lost and the film must contain moisture which causes discomfort
Solution Approach 1:
The patent applies a porous hydrophilic coating material that maintains open pore structure, allowing air and moisture vapor to pass through while providing oil protection. The coating contains interconnected pores that enable breathability unlike continuous non-porous films, eliminating the wet and clammy feeling while maintaining oleophobic properties.
Solution Approach 2:
The patent creates a composite structure combining ePTFE base membrane with a porous hydrophilic coating layer containing hydrophilic polymer particles. This composite material integrates the waterproof breathability of ePTFE with the oil resistance and moisture management of the porous hydrophilic coating, achieving multiple functions simultaneously.
2Object-affected harmful factors
If a hydrophilic coating is applied to protect the membrane from oil, then oleophobic properties are improved, but air flow is blocked causing discomfort
Solution Approach 1:
The coating material is specifically designed with a porous structure containing interconnected voids and channels that allow air molecules to pass through. The porosity enables maintenance of air flow productivity while the hydrophilic polymer particles provide oil protection, resolving the contradiction between protection and air flow.
3Reliability
If the membrane is made from ePTFE material, then hydrophobicity and waterproof properties are improved, but the membrane absorbs oil compromising the properties
Solution Approach 1:
The porous hydrophilic coating is applied to the ePTFE membrane surface before oil contamination can occur. The coating acts as a preliminary protective barrier that prevents oil from reaching and being absorbed by the ePTFE material, while allowing water vapor and air to pass through the porous structure.
Solution Approach 2:
The patent creates a composite material system where the ePTFE base layer provides waterproof reliability and the porous hydrophilic coating layer provides oil resistance. The combination of these two materials with complementary properties resolves the contradiction between maintaining waterproof properties and preventing oil absorption.
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 composite membrane maintains waterproof and wind-resistant properties while preventing oil contamination, providing comfort through air permeability and moisture vapor transmissivity, with improved oleophobic resistance and durability.
Implementation Method 1
The coating material is precipitated on the surfaces of the plurality of nodes and fibrils upon rendering the coating material insoluble in the low surface tension fluid
Implementation Method 2
applied via a low surface tension fluid like supercritical carbon dioxide
Implementation Method 3
The coating material comprises a copolymer formed from a fluorinated acrylate... provides oil and contaminating agent resistance
Data Source
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AI summary
An air permeable composite article (12) that in one embodiment includes a porous base membrane (16) that includes a plurality of nodes (22) and fibrils (24) defining a plurality of interconnecting pores (26) extending through the porous base membrane with each node and fibril having a surface. The composite article also includes a precipitated coating material (28) deposited on the surfaces of the plurality of nodes and fibrils. The coating material includes a copolymer formed from a fluorinated acrylate or methacrylate, an n-alkyl acrylate or methacrylate, and an isocyanate crosslinker. The precipitated coating material provides oil and contaminating agent resistance of at least a number six measured in accordance with AATCC 118 test method.