Composite Membrane Surface Roughness for Tape Adhesion
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Solution Overview
Problem
The adhesion between the separation functional layer and the protective tape in spiral membrane elements is reduced due to the smoothed surface provided by the coating layer, leading to a less effective reinforcing effect.
Innovation Solution
A composite semipermeable membrane with a coating layer having different surface roughnesses due to varying adhesion amounts of the coating material, featuring glossy portions with a surface roughness of 30 nm or less and non-glossy portions with a surface roughness of 50 nm or more, is used to enhance adhesion with the protective tape while maintaining the coating layer's effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer is provided on the surface of the separation functional layer to improve fouling resistance and durability, then the coating layer provides protective benefits, but adhesion between the separation functional layer and protective tape is reduced
Solution Approach 1:
The coating layer is designed with different surface roughness in different regions: a first region with lower surface roughness (Ra ≤ 30 nm) for maintaining fouling resistance, and a second region with higher surface roughness (Ra ≥ 50 nm) for enhancing adhesion with protective tape. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The coating layer is segmented into functionally distinct regions: a first region providing fouling resistance and a second region providing adhesion enhancement. This segmentation allows the coating layer to simultaneously deliver both protective benefits and bonding strength without compromise.
2Object-affected harmful factors
If the coating layer provides a smoothed surface to improve fouling resistance, then contamination resistance is enhanced, but the reinforcing effect of the protective tape is reduced
Solution Approach 1:
The coating layer features local quality variation with a first region having smoothed surface (Ra ≤ 30 nm) for contamination resistance and a second region having rougher surface (Ra ≥ 50 nm) for reinforcing effect. This resolves the contradiction by providing both anti-contamination and reinforcement functions in different locations.
3Strength
If the coating material adhesion amount is increased to improve adhesion, then bonding strength is enhanced, but the coating layer's protective effects are compromised
Solution Approach 1:
The coating layer is segmented into a first region with lower coating material adhesion for maintaining protective effects and a second region with higher coating material adhesion for enhancing bonding strength. This segmentation allows both objectives to be achieved simultaneously without compromise.
Solution Approach 2:
Different regions of the coating layer have different adhesion amounts of coating material: the first region has lower adhesion to preserve protective effects, while the second region has higher adhesion to enhance bonding strength. This local differentiation resolves the contradiction effectively.
Data Source
AI summary
Provided are a composite semipermeable membrane capable of enhancing adhesion between a separation functional layer provided with a coating layer and a protective tape while maintaining an effect of the coating layer to some extent, and a spiral membrane element using the composite semipermeable membrane.A composite semipermeable membrane includes: a porous support; a separation functional layer formed on the porous support; and a coating layer provided on a surface of the separation functional layer, the coating layer having different surface roughnesses due to different adhesion amounts of a coating material depending on locations. The composite semipermeable membrane has a coating layer-side surface on which a glossy portion having a surface roughness Ra of 30 nm or less and a non-glossy portion having a surface roughness Ra of 50 nm or more are provided.