Porous PTFE Membrane Liquid-Repellent Coating for Waterproof Sound Transmission
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Solution Overview
Problem
Conventional gas-permeable membranes with liquid repellency are prone to wrinkling and sagging when cut and integrated into electronic device housings, leading to reduced sound transmission.
Innovation Solution
A porous PTFE membrane coated with a liquid-repellent agent obtained by polymerizing monomers consisting of CH2═CHCOOCH2CH2C6F13, which allows for stretching and reduces deformation, combined with a method involving forming, stretching, and liquid-repellent treatment steps to enhance flexibility and prevent wrinkling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gas-permeable membrane with liquid repellency is used, then liquid repellency is achieved, but the membrane is prone to wrinkling and sagging when cut and integrated into housings
Solution Approach 1:
The patent changes the chemical composition parameters of the liquid-repellent agent by using a fluorine-containing polymer with specific molecular weight (10,000 to 1,000,000) and fluorine content (50 to 90 mass%), which optimizes both liquid repellency and flexibility to prevent wrinkling and sagging
Solution Approach 2:
The patent creates a composite structure by coating the porous PTFE membrane with a fluorine-containing polymer liquid-repellent agent, combining the gas permeability of PTFE with the liquid repellency and flexibility enhancement from the fluorine polymer
2Stability of the object's composition
If the membrane is stretched to reduce wrinkling, then shape stability improves, but liquid repellency may be compromised
Solution Approach 1:
The patent optimizes the physical parameters of the liquid-repellent agent including molecular weight (10,000 to 1,000,000) and fluorine content (50 to 90 mass%) to ensure that the coating maintains liquid repellency even after the membrane is stretched during integration
3Object-generated harmful factors
If a thin membrane is used for good sound transmission, then sound transmission improves, but the membrane becomes more susceptible to deformation
Solution Approach 1:
The patent changes the mechanical properties of the thin membrane by coating it with a fluorine-containing polymer that enhances flexibility and reduces deformation, allowing the membrane to remain thin for good sound transmission while resisting deformation during cutting and integration
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 membrane achieves sufficient liquid repellency and reduced wrinkling and sagging, maintaining sound pressure loss of 2.0 dB or less and elongation at break between 200 to 600%, ensuring effective sound transmission and waterproofing.
Implementation Method 1
Even if a highly water-repellent porous PTFE membrane is used as a gas-permeable membrane, entry of a liquid with a low surface tension cannot be fully prevented
Implementation Method 2
a gas-permeable membrane having a porous polytetrafluoroethylene (PTFE) membrane is suitable... imparted with liquid repellency
Implementation Method 3
a gas-permeable membrane that allows passage of gasses but prevents entry of water
Implementation Method 4
a gas-permeable membrane having a porous polytetrafluoroethylene (PTFE) membrane
Implementation Method 5
Rf groups having 8 or more carbon atoms have significantly higher crystallinity than Rf groups having a smaller number of carbon atoms... The receding contact angle increases with increasing crystallinity
Data Source
AI summary
The present invention provides a porous polytetrafluoroethylene membrane having a surface coated with a liquid-repellent agent. In this porous polytetrafluoroethylene membrane, the liquid-repellent agent is a polymer obtained by polymerization of monomers consisting essentially of CH2═CHCOOCH2CH2C6F13. This porous polytetrafluoroethylene membrane is suitable for use as a gas-permeable membrane that allows passage of gases but prevents entry of liquids and/or dust, specifically as a waterproof sound-transmitting membrane, a waterproof gas-permeable membrane, or a dustproof gas-permeable membrane.