Aqueous Wetting of PTFE Microporous Membranes With Low VOC Coatings
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Solution Overview
Problem
Conventional solvent-based coating systems for low surface energy substrates, such as polytetrafluoroethylene (PTFE), face challenges including high VOC emissions, environmental concerns, and limited compatibility with aqueous fluoropolymers, making it difficult to achieve stable and fast wetting without compromising water repellency.
Innovation Solution
An aqueous delivery system using surfactants and water-insoluble wetting agents like alcohols with C5-C10 linear chains, along with stabilizers and functional additives, to lower surface tension and facilitate wetting of low surface energy substrates without phase separation, enabling the delivery of a range of materials, including oleophobic polymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solvent-based coating systems are used to wet low surface energy substrates, then wetting performance is improved, but VOC emissions increase and environmental compatibility worsens
Solution Approach 1:
The invention changes the fundamental parameter of the coating system from solvent-based to aqueous-based, while modifying the surface tension of the aqueous system through surfactant addition to achieve wetting performance comparable to solvent systems without the harmful VOC emissions
Solution Approach 2:
Surfactants act as intermediaries between the aqueous coating system and the low surface energy substrate, reducing surface tension and enabling the aqueous system to wet the substrate effectively without requiring volatile organic solvents
2Object-generated harmful factors
If aqueous coating systems are used to reduce VOC emissions, then environmental compatibility is improved, but wetting capability on low surface energy substrates deteriorates
Solution Approach 1:
The surface tension of the aqueous coating system is deliberately reduced through the addition of surfactants, changing the physical parameter that governs wetting behavior to enable effective coating of low surface energy substrates
Solution Approach 2:
Surfactants serve as intermediary substances that facilitate the interaction between the aqueous coating and the hydrophobic substrate, enabling wetting through surface tension reduction without compromising the environmental benefits of an aqueous system
3Reliability
If high surfactant concentrations are used to achieve wetting, then wetting performance is improved, but emulsion stability deteriorates
Solution Approach 1:
The invention optimizes the concentration parameter of surfactants to achieve the minimum effective level for wetting while maintaining emulsion stability, and adjusts other formulation parameters such as pH and ionic strength to enhance both wetting and stability simultaneously
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 aqueous system effectively wetts low surface energy substrates, allowing for uniform coatings that maintain air permeability and flexibility, while reducing VOC emissions and expanding compatibility with a broader range of additives, thus overcoming the limitations of solvent-based systems.
Implementation Method 1
An aqueous delivery system is produced when at least one surfactant is used to lower the surface tension of water
Implementation Method 2
at least one water-insoluble wetting agent is emulsified by the surfactant(s) in the aqueous delivery system
Implementation Method 3
The aqueous delivery system is applied to a low surface energy substrate... Spontaneous wetting occurs when the surface energy between the solid and liquid, γSL is less than the surface energy between the solid and air, γSA
Implementation Method 4
In order for a latex to spread across the substrate surface and form a uniform coating, it is necessary for it to 'wet' the substrate to which it is applied. 'Wetting' results when the contact angle, θ, between the aqueous latex and the solid substrate is less than about 90 degrees
Data Source
AI summary
An aqueous delivery system is described including at least one surfactant and at least one water insoluble alcohol. Further described are low surface energy substrates, such as microporous polytetrafluoroethylene, coated with such an aqueous solution so as to impart a change in at least one surface characteristic compared to the surface characteristics of the uncoated low surface energy substrate.