PVDF Substrate Bonding for PS PES Membranes
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Solution Overview
Problem
Current filtration apparatus face challenges in bonding polysulfone (PS) or polyethersulfone (PES) membranes to substrates due to skin formation during contact welding, and existing methods like laser, RF, vibration, and solvent welding either fail to produce strong bonds or result in particle generation or substrate degradation from caustic sterilization and gamma radiation exposure.
Innovation Solution
Heat bonding PS or PES membranes to polyvinylidene fluoride (PVDF) substrates, where the PVDF is partially melted to infiltrate the membrane pores, creating a strong and stable bond resistant to gamma radiation and caustic exposure, using a heating element with an anti-stick surface and pressure to ensure intimate contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If contact welding is used to bond PS or PES membranes to substrates, then bonding strength is improved, but skin formation occurs during the process which prevents good plate to plate bonding
Solution Approach 1:
The patent changes the material parameter from PS/PES to PVDF, which has different thermal properties. PVDF can be contact welded without forming a skin because its melting and bonding characteristics differ from PS/PES, allowing the heating element to be removed and plates pressed together before skin formation occurs.
Solution Approach 2:
The patent uses composite material construction with PVDF substrates and PS/PES membranes as separate components. The PVDF substrate provides the weldable structural component while the PS/PES membrane provides the filtration function, allowing each material to be optimized for its specific function without the conflicting requirements of a single material system.
2Strength
If PS or PES membranes are heat bonded to acrylic substrates, then bonding is achieved, but caustic resistance is lost
Solution Approach 1:
The patent employs a composite material system where PVDF substrates provide both structural integrity and caustic resistance, while PS/PES membranes provide filtration performance. This separation of functions allows each material to be selected for its optimal properties without compromise.
Solution Approach 2:
The patent adopts a disposable filtration element design where the entire assembly including PVDF substrate and membrane is designed for single use. This eliminates the need for repeated sterilization cycles that would degrade reusable components, ensuring consistent performance for the duration of use.
3Ease of manufacture
If laser or RF welding is used to bond PS or PES plates, then bonding is achieved, but bond strength is insufficient
Solution Approach 1:
The patent replaces advanced welding technologies (laser, RF) with simple contact welding mechanics. The PVDF material properties enable effective bonding through basic heating and pressing operations, eliminating the need for complex welding systems while achieving superior bond strength.
4Strength
If vibration or ultrasonic welding is used to bond PS or PES plates, then bonding is achieved, but particle generation occurs which is undesirable
Solution Approach 1:
The patent replaces vibration and ultrasonic welding mechanisms with thermal contact welding. This substitution eliminates the mechanical agitation that generates particles, using instead controlled heating to achieve bonding without disrupting the material structure or generating contaminants.
5Strength
If solvent welding with methylene chloride is used to bond PS or PES plates, then bonding is achieved, but the membrane material is changed or dissolved
Solution Approach 1:
The patent replaces chemical solvent welding with thermal contact welding. This substitution eliminates the need for aggressive solvents like methylene chloride, using instead controlled heating to melt and bond the PVDF material, thereby preserving the chemical integrity and composition of the membrane and substrate materials.
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 method provides a strong, stable bond between the membrane and substrate, allowing for easy assembly and resistance to caustic sterilization and gamma radiation, while avoiding previous issues of skin formation and particle generation, resulting in a reliable filtration device.
Implementation Method 1
Heat bonding is effected by applying a heating element under pressure to a membrane comprising PS or PES... which, in turn, is in contact with the PVDF substrate in order to partially melt the PVDF substrate
Implementation Method 2
the molten PVDF infiltrates the PS or PES membrane pores
Implementation Method 3
The heating element is removed and the molten PVDF is cooled to solidify it
Data Source
Figure 1
Figure 2
AI summary
A laminate is provided comprising at least one polysulfone and/or polyethersulfone porous membrane heat bonded to a polyvinylidene fluoride substrate.